Octagonal end roof
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Transcript of Octagonal end roof
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Octagonal Roof
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Notes to this Lesson• This demonstration develops from knowledge
gained from the development of Gable & Hip Roofs
• This PowerPoint does not explain the development of the Basic Roof Members
• If you require an understanding of these you should first look at the Gable & Hip Roof presentations
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Lesson ParametersTo be Provided by Trainer and used in Confirmation Excercises
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Critical Definition
• Plan Length • Is the distance a roofing member travels,
measured along the base of the Right Angled Triangle that it forms adjacent to the Pitch angle.
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Example
• In its most common form
PLAN LENGTH
27°
Pitch Angle
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Example
• Other Examples
PLAN LENGTH
27°
PL
AN
LE
NG
TH
27°
PLAN L
ENGTH
27°
PLAN LENGTH
27°
Pitch Angle
Pitch Angle
Pitch Angle
Pitch Angle
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Hip Rafter per 1m of Common Rafter Plan Length
½ Span
½ Span½ Span
22.5
°Plan Lengths
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Confirmation of Learning
• Determine which side is the “Plan Length”
27°
27°
63°
90°
63°
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Confirmation of Learning - Answer
• Determine which side is the “Plan Length”
27°
PLAN LENGTH
27°
63°
90°
63°
PLAN LENGTH
PL
AN
LE
NG
TH
PL
AN
LE
NG
TH
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Confirmation of Learning
• What are the Plan Lengths of these triangles?
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Confirmation of Learning - Answer
Plan Lengths
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Confirmation of Learning
25° 247
This Triangle
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Confirmation of Learning
25° 247
PLA
N LE
NG
TH
This Triangle
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Octagonal Roof
• A Regular Geometric Shape
1/2 SPAN
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Roof Members can be Determined
MAJOR CROWN END
CE
NT
RE
ING
RA
FT
ER
CE
NT
RE
ING
RA
FT
ER
MIN
OR CROW
N END
MINOR CROW
N END
HIP
RA
FT
ER
HIP RAFTER
HIP RAFTER
HIP
RA
FT
ER
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Class Works
• On an A3 drawing sheet conduct the following drafting excercise
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1/2 SPANWalls are parallel
Determine Set Out Points
Gathering Point is ½ Span Back from edge
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1/2 SPANWalls are parallel
Determine Set Out Points
Gathering Point is ½ Span Back from edgeThis will mean for our Practical Class Exercise, the Gathering Point will be ½ Rafter in from edge of the Table Frame
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Drawing Octagonal Roof without Compass
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Drawing An Octagonal End Roof
Draw 2 Construction Lines to scale to represent the Width of The Building
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Drawing An Octagonal End RoofBUILDING LENGTH
Draw Construction Line To Represent End of Building
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Drawing An Octagonal End RoofBUILDING LENGTH
Draw Construction Line To Represent End of Building
This end is not so important
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Drawing An Octagonal End RoofBUILDING LENGTH
==
Draw a Construction Line Mid Span to Represent the Ridgeline (i.e. Centre Span)
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Drawing An Octagonal End Roof
1/2 SPAN
BUILDING LENGTH
==
Locate Centring Rafters(1/2 Span from end)
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Drawing An Octagonal End Roof
1/2 SPAN
BUILDING LENGTH
==
Find Gathering Point
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Drawing An Octagonal End Roof
1/2 SPAN
BUILDING LENGTH
==
Scribe Semi Circle with ½ Span as Radius
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Drawing An Octagonal End Roof
1/2 SPAN
Draw in Centring Rafters
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Drawing An Octagonal End Roof
MAJOR CROWN
CE
NT
RE
ING
RA
FT
ER
CE
NT
RE
ING
RA
FT
ER
Draw in Major Crown End
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Drawing An Octagonal End Roof
MAJOR CROWN END
CE
NT
RE
ING
RA
FT
ER
CE
NT
RE
ING
RA
FT
ER
=
=
=
=
Bisect Centring & Crown End Rafters to form Minor Crown End
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Drawing An Octagonal End Roof
MAJOR CROWN END
CE
NT
RE
ING
RA
FT
ER
CE
NT
RE
ING
RA
FT
ER
45°
45°
45°
45°
Bisect Centring & Crown End Rafters to form Minor Crown End
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Drawing An Octagonal End Roof
MAJOR CROWN END
CE
NT
RE
ING
RA
FT
ER
CE
NT
RE
ING
RA
FT
ER
45°
45°
45°
45°
Extend Lines Perpendicular to RidgeAt ½ End Length= ½ Span x 0.414
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Drawing An Octagonal End Roof
MAJOR CROWN END
CE
NT
RE
ING
RA
FT
ER
CE
NT
RE
ING
RA
FT
ER
45°
45°
45°
45°
Extend Sides of Building by ½ End Length= ½ Span x 0.414
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Drawing An Octagonal End Roof
MAJOR CROWN END
CE
NT
RE
ING
RA
FT
ER
CE
NT
RE
ING
RA
FT
ER
45°
45°
45°
45°
Join up external Lines
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Drawing An Octagonal End Roof
MAJOR CROWN END
CE
NT
RE
ING
RA
FT
ER
CE
NT
RE
ING
RA
FT
ER
45°
45°
45°
45°
Draw in Hips
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Draw Octagonal End With Compass
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Drawing An Octagonal End Roof
Draw 2 Construction Lines to scale to represent the Width of The Building
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Drawing An Octagonal End RoofBUILDING LENGTH
Draw Construction Line To Represent End of Building
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Drawing An Octagonal End RoofBUILDING LENGTH
Draw Construction Line To Represent End of Building
This end is not so important
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Drawing An Octagonal End RoofBUILDING LENGTH
==
Draw a Construction Line Mid Span to Represent the Ridgeline (i.e. Centre Span)
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Drawing An Octagonal End Roof
1/2 SPAN
BUILDING LENGTH
==
Locate Centring Rafters(1/2 Span from end)
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Drawing An Octagonal End Roof
1/2 SPAN
BUILDING LENGTH
==
Find Gathering Point
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Drawing An Octagonal End Roof
1/2 SPAN
BUILDING LENGTH
==
Scribe Semi Circle with ½ Span as Radius
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Drawing An Octagonal End Roof
1/2 SPAN
Draw in Centring Rafters
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Drawing An Octagonal End Roof
MAJOR CROWN
CE
NT
RE
ING
RA
FT
ER
CE
NT
RE
ING
RA
FT
ER
Draw in Major Crown End
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Drawing An Octagonal End Roof
MAJOR CROWN END
CE
NT
RE
ING
RA
FT
ER
CE
NT
RE
ING
RA
FT
ER
=
=
=
=
Bisect Centring & Crown End Rafters to form Minor Crown End
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Drawing An Octagonal End Roof
MAJOR CROWN END
CE
NT
RE
ING
RA
FT
ER
CE
NT
RE
ING
RA
FT
ER
MIN
OR CROW
N END
MINOR CROW
N END
22,5°22,5°
22,5°
22,5°
22,5°22,5°
22,5
°
22,5
°
Bisect Centring & all Crown End Rafters to form Hip Rafters as extended “Light” Construction Lines
![Page 47: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/47.jpg)
MAJOR CROWN END
CE
NT
RE
ING
RA
FT
ER
CE
NT
RE
ING
RA
FT
ER
MIN
OR CROW
N END
MINOR CROW
N END
22,5°22,5°
22,5°
22,5°
22,5°22,5°
22,5
°
22,5
°
Drawing An Octagonal End Roof
Extend Lines Perpendicular to RidgeTo intersect with HIP
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MAJOR CROWN END
CE
NT
RE
ING
RA
FT
ER
CE
NT
RE
ING
RA
FT
ER
MIN
OR CROW
N END
MINOR CROW
N END
22,5°22,5°
22,5°
22,5°
22,5°22,5°
22,5
°
22,5
°
Drawing An Octagonal End Roof
Extend sides of BuildingTo intersect with HIP
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MAJOR CROWN END
CE
NT
RE
ING
RA
FT
ER
CE
NT
RE
ING
RA
FT
ER
MIN
OR CROW
N END
MINOR CROW
N END
22,5°22,5°
22,5°
22,5°
22,5°22,5°
22,5
°
22,5
°
Drawing An Octagonal End Roof
Clean Up & Draw in HIPS
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MAJOR CROWN END
CE
NT
RE
ING
RA
FT
ER
CE
NT
RE
ING
RA
FT
ER
MIN
OR CROW
N END
MINOR CROW
N END
22,5°22,5°
22,5°
22,5°
22,5°22,5°
22,5
°
22,5
°
Drawing An Octagonal End Roof
Join up external lines
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Confirmation of Learning
• On the A3 Paper Supplied, Draw to scale and Octagonal End Roof based on the following
• Building Length = 7600mm
• Building Width = 4500mm
• Correctly Label all Roof Members
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Answer
• Retain your drawing for future use and submission.
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Review Geometry
Angle Between Major Crown End & Centring Rafters = 90⁰
All Angles are plan angles
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Clean Up Drawing
Angle Between Crown End Rafters = 45⁰
All Angles are plan angles
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Clean Up Drawing
Angle Between Crowns Ends & Hips = 22.5⁰
All Angles are plan angles
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Angles formed by the Roof
These angles are the same no matter the size of Roof as it is a Geometric Shape
All Angles are plan angles
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Octagonal Roof TheoryIf the angle between the members is constant 22.5⁰
We can say in all cases, no matter the size of the roof½ End = ½ Span x tan 22.5⁰
= ½ Span x 0.414
All Angles are plan angles
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If the angle between the members is constant 22.5⁰
We can say in all cases, no matter the size of the roof
½ End = ½ Span x 0.414
Octagonal Roof Theory
The Triangles are the same
All Angles are plan angles
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If the angle between the members is constant 22.5⁰
We can say in all cases, no matter the size of the roof
½ End = ½ Span x 0.414
Octagonal Roof Theory
The Triangles are the same
All Angles are plan angles
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If the angle between the members is constant 22.5⁰
We can say in all cases, no matter the size of the roof
½ End = ½ Span x 0.414
Octagonal Roof Theory
Top Plate Projection= ½ End
All Angles are plan angles
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If the angle between the members is constant 22.5⁰
In all cases, we can say
Full End = ½ Span x 0.414 x 2
Octagonal Roof Theory
All Angles are plan angles
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If the angle between the members is constant 22.5⁰
Also in all cases, the full end will be
Full End = ½ Span x 0.828
Octagonal Roof Theory
All Angles are plan angles
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These formulas are the same no matter the size of the Roof
Top Plate Projection = ½ Span x 0.414 (Also ½ End)Full End = ½ Span x 0.828
Octagonal Roof Theory
Top Plate Projection
Ful
l End
s
NOTE – These are all Centreline Measurements
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3. Set Out Roof
• t
22.5° between Roof Members
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2. Set Out Roof
22.5° between Roof Members
(a) Top Plate projection = Tan 22.5°
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2. Set Out Roof(b) Octagonal End = 2 x Tan 22.5°
2X
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2. Worked Example
• Based on the dimensions on the example sheet previous drafting exercise determine,
Top Plate Projection½ Span x 0.414 = 3800 x 0.414 = 931.5
Octagonal End ½ Span x 0.828 = 3800 x 0.828 = 1863
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Confirmation of Learning
• Based on the full size dimensions given to you by your trainer determine,
1.Top Plate Projection
2.Octagonal End
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Confirmation of Learning - Answer
• Based on the full size dimensions used in your previous drafting exercise determine,
(Click on Spread Sheet Below to Check Answers)
Span (mm) 76001/2 Span 3800
Top Plate Projection 1574Octagonal End 3148
Entry only allowed in this cell
Note minor discrepancies are rounding errors
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Determine Roof Members
• As with all previous roof
• We must solve the 1m triangle
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Solve 1m Triangle - Example(3a) Rafter Length per plan 1m of Travel of Rafter in Plan
• Rafter Length per 1m = 1 ÷ Cos 22.5° = 1.082 (This is the Rafter Multiplier)
22.5°
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Solve 1m Triangle - Example3(b) Rise per plan 1m Travel of Rafter in Plan
• Rise = 1 x Tan 22.5° = 0.414 (This is the Rise Multiplier)
1.082
22.5°
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Solve 1m Triangle - Example3(c) Hip Rafter Plan Length per 1m Travel of Rafter in Plan
Lets have a close look at why the Plan Length of Hip is ALWAYS 1.082 for every 1m of Rafter plan length
1.082
0.41
4
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The Octagonal Roof is a geometric shape
No matter the size the angles are always the same
Plan Length Hip Rafter
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The Octagonal Roof is a geometric shape
No matter the size the angles are always the same
Plan Length Hip Rafter
These angles are always 90⁰
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The Octagonal Roof is a geometric shape
No matter the size the angles are always the same
Plan Length Hip Rafter
These angles are always 45⁰
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The Octagonal Roof is a geometric shape
No matter the size the angles are always the same
Plan Length Hip Rafter
These angles are always 22.5⁰
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These relationships are constant on all properly built Octagonal Roofs
Plan Length Hip Rafter
These angles are always 22.5⁰
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Calculate Plan Length of Hip
Method 1
Plan Hip Length = √((1/2 Span)² (1/2 Span x 0.414)²) = 1.082 per 1m of Rafter Plan Length
Plan Length Hip Rafter
Hip Rafters
1.082
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Calculate Plan Length of Hip
Method 2
Plan Hip Length = ½ Span ÷ cos 22.5⁰ = 1.082 per 1m of Rafter Plan Length
Plan Length Hip Rafter
1.082
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Calculate Plan Length of Hip
Method 2
Plan Hip Length = ½ Span ÷ cos 22.5⁰ = 1.082 per 1m of Rafter Plan Length
Plan Length Hip Rafter
1.082
The Hip Plan Length isAlways 1.082 x ½ Span
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Hip Rafter per 1m of Common Rafter Plan Length
In ALL Cases Plan Length Hip =1.082 x ½ Span
½ Span
½ Span½ Span
22.5
°
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= Tan 22.5° x 1= 1.082Note – This is always the case regardless of Pitch
Solve 1m Triangle - Example2(c) Hip Rafter Plan Length per 1m Travel of Rafter in Plan
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Solve 1m Triangle - Example2(d) Hip Rafter Length per 1m Travel of Rafter in Plan
Hip Length / m = √(0.4142 + 1.0822 )= √(0.171 + 1.171)= 1.159
(This is the Hip Rafter Multiplier per 1m of Rafter in plan)
1.082
22.5°
0.41
4
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Solve 1m Triangle - Example2(e) Hip Pitch = Tan-1 (Rise per metre ÷ 1.082)
Hip Pitch = Tan-1(RISE ÷ 1.082) = Tan-1(0.414 ÷ 1.082) = Tan-1(0.383) = 20.9° say 21°
1.082
22.5°
0.41
4
1.159
Remember this is always 1082
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1m Triangle Multipliers - Example
1.082
22.5°
1.159
20.9°
As with previous Roofs the 1m triangle will be the basis of your calculation of Roof Members
Common Rafter Multiplier Hip Rafter Multiplier
0.41
4
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Confirmation of Learning
• On your worksheet Solve the 1m triangle and determine the multipliers for the Roof Pitch given to you by your trainer
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1m Triangle - Answer
Click on table below to open Spread sheet
Pitch Given to Learners 25.0 °
a. Rafter Length per 1m Travel of Rafter in Plan b. Rise per plan 1m Travel of Rafter in Plan c. Hip Rafter Plan Length per 1m Travel of Rafter in Pland. Hip Rafter Length per 1m Travel of Rafter in Plane. Hip Pitch 23.315
Answers1.1030.4661.0821.178
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4. RISE
22.5°
1/2 SPAN
RIS
E
Rise is Calculated to the Pitching Line
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22.5°
3800
RIS
E =
4. Rise
(a) Rise = ½ Span x Rise per metre (Note –Rise is calculated to pitching line)
Rise Multiplier
For every 1m of Plan Travel, the Roof Rises 0.414m
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22.5°
3800
RIS
E =
157
4
4. Rise
(a) Rise = ½ Span x Rise per metre (Note –Rise is calculated to pitching line)
Rise = 3800 x 0.414 = 1574
For every 1m of Plan Travel, the Roof Rises 0.414m
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4. RISE
22.5°
3800
RIS
E =
157
4
Remember that rise is calculated to the pitching line
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4. RISE
22.5°
3800
TO
TA
L R
ISE
The full height is calculated by determining Total Rise
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4. RISE4(b) Total Rise
22.5°
3800
TO
TA
L R
ISE
Total Rise is a 3 Step process
1.Determine Required Height above Pitching Line Perpendicular to Rafter Total Rise
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224
38
45
17
10
152Total Rise
Total Rise is a 3 Step process
1.Determine Required Height above Pitching Line Perpendicular to Rafter
Pitching Line
AllowancesRafter = 152Battens = 45Custom Orb = 17Ridge Cap = 10
Total = 224Note Rafter 190 x 3538mm Birdsmouth152 above Pitching Line
(All measurements perpendicular to Rafter)
4. RISE4(b) Total Rise
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4. RISE4(b) Total Rise
22.5°
3800
TO
TA
L R
ISE
224
Total Rise is a 3 Step process
1.Determine Required Height above Pitching Line Perpendicular to Rafter Total Rise
AllowancesRafter = 152Battens = 45Custom Orb = 17Ridge Cap = 10
Total = 224
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4. RISE4(b) Total Rise
22.5°
3800
PLU
MB
HE
IGH
T
224
Total Rise is a 3 Step process
1.Determine Required Height above Pitching Line Perpendicular to Rafter2.Determine Plumb Height
Total Rise
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4. RISE4(b) Total Rise
22.5°
3800
PLU
MB
HE
IGH
T
224
90°
67.5°
Total Rise is a 3 Step process
1.Determine Required Height above Pitching Line Perpendicular to Rafter2.Determine Plumb Height
To determine Plumb HeightWe must solve the HypotenuseOf this Triangle
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4. RISE4(b) Total Rise
22.5°
3800
PLU
MB
HE
IGH
T
224
90°
67.5°
Total Rise is a 3 Step process
1.Determine Required Height above Pitching Line Perpendicular to Rafter2.Determine Plumb Height
This must be a Right Angle
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4. RISE4(b) Total Rise
22.5°
3800
PLU
MB
HE
IGH
T
224
90°
67.5°
Total Rise is a 3 Step process
1.Determine Required Height above Pitching Line Perpendicular to Rafter2.Determine Plumb Height
This must be a 90° - Roof Pitch
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4. RISE4(b) Total Rise
22.5°
3800
PLU
MB
HE
IGH
T
224
90°
67.5°
Total Rise is a 3 Step process
1.Determine Required Height above Pitching Line Perpendicular to Rafter2.Determine Plumb Height
This also must be a 90° - Roof Pitch
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4. RISE4(b) Total Rise
224
67.5°
22.5°
242
Total Rise is a 3 Step process
1.Determine Required Height above Pitching Line Perpendicular to Rafter2.Determine Plumb Height
This must equal the Roof Pitch
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4. RISE4(b) Total Rise
224
67.5°
22.5°
Total Rise is a 3 Step process
1.Determine Required Height above Pitching Line Perpendicular to Rafter2.Determine Plumb Height
This is a similar triangle thatWe used to determine the Rafter Multiplier
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4. RISE4(b) Total Rise
224
67.5°
22.5°
242
Total Rise is a 3 Step process
1.Determine Required Height above Pitching Line Perpendicular to Rafter2.Determine Plumb Height Plumb Height = Amount Left On x Rafter Length per metre = 224 x 1.082 = 242
To determine HypotenuseWe multiply “Amount Left onBy Rafter Multiplier”
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4. RISE4(b) Total Rise
22.5°
3800
224
90°
67.5°
67.5°
22.5°
242
157
4
TO
TA
L R
ISE
= 1
816
Total Rise is a 3 Step process
1.Determine Required Height above Pitching Line Perpendicular to Rafter2.Determine Plumb Height = 2423.Add answer to Rise
Rise = 1574Plumb Height = 242Total Rise = 1816
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4. RISE4(b) Total Rise
22.5°
3800
90°
67.5°
67.5°
22.5°
164
1574 17
38
152
Total Rise is a 3 Step process
1.Determine Required Height above Pitching Line Perpendicular to Rafter2.Determine Plumb Height = 2423.Add answer to Rise
Rise = 1574Plumb Height = 164 (152 x 1.082)Total Rise = 1738
If you wanted to find the height toTop of Rafter – you would substitute the perpendicular distance to the top of Rafter
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Confirmation of Learning• Based on data
– Span To be Supplied by Trainer– Pitch To be Supplied by Trainer– Timber Depth To be Supplied by Trainer
Timber Depth is used to determine amount left on
Determine1.Rise2.Amount Left On Plumb Height
3.Total Rise
Click on Spread sheet to determine answers
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Confirmation of Learning - Answer• Based on data
– Span To be Supplied by Trainer– Pitch To be Supplied by Trainer– Timber Depth To be Supplied by Trainer
Timber Depth is used to determine amount left on
Determine1.Rise2.Amount Left On Plumb Height
3.Total Rise
Click on Spread sheet to determine answers
Roof Pitch 22.5Span 7600Amount Left On 152
Amount Left On Plumb Height 165Rise 1574Total Rise 1739
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(5) Major Crown End Rafter
RA
FT
ER
MAJOR CROWN
½ SPAN
½ S
PA
N
(a)Centreline Length
How far does it travel in “Plan” ?
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(a)Centreline Length
How far does it travel in “Plan” ?
(5) Major Crown End Rafter
1/2
SP
AN
1/2 SPAN
RIS
E
1/2 SPAN
PLUMB CUT
ROOF PITCH
RIDGE
Rafter Travels toGathering Point
Plan View
Side Elevation
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(a) Centreline Length
How far does it travel in “Plan” ?
(5) Major Crown End Rafter
RA
FT
ER
MAJOR CROWN
½ SPAN
½ S
PA
N
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1/2
SP
AN
1/2 SPAN
RIS
E
1/2 SPAN
PLUMB CUT
ROOF PITCH
RIDGE
(a) Centreline Length, Which Multiplier?
(5) Major Crown End Rafter
Plan Length = ½ Span
The Rise must be the same as
1.Common Rafter
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1/2
SP
AN
1/2 SPAN
RIS
E
1/2 SPAN
PLUMB CUT
ROOF PITCH
RIDGE
(a) Centreline Length, Which Multiplier?
(5) Major Crown End Rafter
Plan Length = ½ Span
The Rise must be the same as
1.Common Rafter
The Plan Length is the same as
1. Common Rafter
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1/2
SP
AN
1/2 SPAN
RIS
E
1/2 SPAN
PLUMB CUT
ROOF PITCH
RIDGE
(a) Centreline Length, Which Multiplier?
(5) Major Crown End Rafter
Plan Length = ½ Span
The Rise must be the same as
1.Common Rafter
The Plan Length is the same as
1.Common Rafter
The Pitch must be the same as
1. Common Rafter
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1/2
SP
AN
1/2 SPAN
RIS
E
1/2 SPAN
PLUMB CUT
ROOF PITCH
RIDGE
(a) Centreline Length, Which Multiplier?
(5) Major Crown End Rafter
The Rise must be the same as
1.Common Rafter
The Plan Length is the same as
1.Common Rafter
The Pitch must be the same as
1. Common Rafter
We use the Common Rafter Multiplier = Rafter Length per metre
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1m Triangle Multipliers
1.082
22.5°
0.41
4
1.159
20.9°
Common Rafter Multiplier
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(a) Centreline Length = ½ Span x Rafter Length per m
How far does it travel in “Plan” ?
(5) Major Crown End Rafter
RA
FT
ER
MAJOR CROWN
½ SPAN
½ S
PA
N
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Worked ExampleExercise 5a
• Determine Major Crown End Centreline Length• Span = 7600• Pitch = 22.5°
Centreline Length = Plan Length x Rafter Length per m
Note – Plan Length = ½ Span
Centreline Length = 3800 x 1.082= 4112
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Confirmation of Learning Exercise 5a
• Based on data given to you by you trainer determine,
Centreline Length Major Crown
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Confirmation of Learning - AnswerExercise 5a
• Based on data given to you by you trainer determine,
Centreline Length Major CrownClick on Spread Sheet to determine answers
°
Centreline Length = 3800 x 1.082= 4113
SpanPitch
760022.5
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5. Major Crown End(b) True LengthHow far does it Travel in Plan ?
RA
FT
ER
MAJOR CROWN
½ SPAN
½ S
PA
N
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5. Major Crown End(b) True LengthHow far does it Travel in Plan ?
Cen
trin
g R
afte
r
½ Span – ½ Rafter
RIS
E
½ Span – ½ Rafter ROOF PITCH
RIDGE
True Length Rafter
Travels to edge ofCentring Rafter
Major Crown End
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5. Major Crown End(b) True LengthHow far does it Travel in Plan ?
RA
FT
ER
MAJOR CROWN
½ SPAN - ½ Rafter
½ S
PA
N
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5. Major Crown End(b) True Length= (½ Span – ½ Rafter) x Rafter Length per m
RA
FT
ER
MAJOR CROWN
½ SPAN - ½ Rafter
½ S
PA
N
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Worked ExampleExercise 5b
• Determine Major Crown End Centreline Length• Span = 7600• Pitch = 22.5°• Rafter Width = 35mm (1/2 Rafter = 35 ÷ 2)• True Length = Plan Length x Rafter Length per m
– Note Plan Length = ½ Span – ½ Rafter
True Length = (3800 – (35 ÷ 2)) x 1.082= (3800 – 17.5) x 1.082
= 3782.5 x 1.082= 4093
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Confirmation of LearningExercise 5a
• Based on data given to you by you trainer determine,
True Length Major Crown End Rafter
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Confirmation of Learning - AnswerExercise 5a
• Based on data given to you by you trainer determine,
True Length Major Crown End RafterClick on Spread Sheet to determine answers
°Rafter Thickness mm
Centreline Length = 3783 x 1.082= 4094
SpanPitch
760022.5
35
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5. Major Crown End(i) Plumb Cut Graphically
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Establish False Top Plate
5. Major Crown End(i) Plumb Cut Graphically
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Establish ½ Span
5. Major Crown End(i) Plumb Cut Graphically
![Page 131: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/131.jpg)
Establish Rise
5. Major Crown End(i) Plumb Cut Graphically
![Page 132: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/132.jpg)
Plumb Cut
Establish Crown End Rafter
5. Major Crown End(i) Plumb Cut Graphically
![Page 133: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/133.jpg)
Plumb Cut
Establish Crown End Rafter
•Rise is Same as Common Rafter•Plan Length is Same as Common Rafter
5. Major Crown End(i) Plumb Cut Graphically
![Page 134: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/134.jpg)
Plumb Cut
Establish Crown End Rafter
•Rise is Same as Common Rafter•Plan Length is Same as Common Rafter•Plumb Cut must be the same as Common Rafter
5. Major Crown End(i) Plumb Cut Graphically
![Page 135: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/135.jpg)
Confirmation of Learning
• On the Drawing previously developed based on data given to you by your Trainer by the Graphical Method shown to you develop on an A3 Sheet,
• (Trainer should select a pitch between 15 to 35°)
Plumb Cut - Major Crown End
![Page 136: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/136.jpg)
Confirmation of Learning - Answer
• On the Drawing previously developed based on data given to you by your Trainer by the Graphical Method shown to you develop on an A3 Sheet,
Plumb Cut - Major Crown End- Print Answer Drawing 1 on a clear sheet to compare with learners
submissions will provide angles from 15 to 35°
![Page 137: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/137.jpg)
15°
20°
25°30°
35°Answer Drawing 1 – Click on Drawing to Open File
![Page 138: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/138.jpg)
5. Major Crown End(ii) Plumb Cut – Steel Square Method
![Page 139: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/139.jpg)
Plumb Cut – Steel Square Method5. (ii) – Worked Example
1.082
22.5°
0.41
4
1.159
20.9°
Common Rafter Multiplier
Run
Rafter Plumb Cut
Rise = 0.414 ÷ 2 = 0.207
Run = 1.000 ÷ 2 = 0.500
Rise
![Page 140: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/140.jpg)
Plumb Cut – Steel Square Method5. (ii) – Worked Example
1.082
22.5°
0.41
4
1.159
20.9°
Common Rafter Multiplier
Run = 500
Rafter Plumb Cut
Rise = 414 ÷ 2 = 207
Run = 1000 ÷ 2 = 500
Rise = 207
![Page 141: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/141.jpg)
Plumb Cut – Steel Square Method5. (ii)
1.082
22.5°
0.41
4
1.159
20.9°
Common Rafter Multiplier
Run
Rafter Plumb Cut
The Steel Square relies on principle of similar triangles
If we reduce the 1m by half the angles will stay the same
Rise
![Page 142: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/142.jpg)
Confirmation of Learning
• Based on the Roof Pitch given to you by the Trainer, Determine the required measurements to set the Steel Square for
– Plumb Cut Major Crown
![Page 143: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/143.jpg)
Confirmation of Learning - Answer
• Based on the Roof Pitch given to you by the Trainer, Determine the required measurements to set the Steel Square for
– Plumb Cut Major Crown– Click on Spread Sheet for Answers
Roof Pitch 22.5
Rise 207Run 500
![Page 144: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/144.jpg)
Plumb Cut Offset Method
![Page 145: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/145.jpg)
22.5°
22438
45
17
10
3800
152
90°
5. Major Crown End(ii) Plumb Cut Offset Method
Total of Internal angles of Triangle formed by Roof = 180°
![Page 146: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/146.jpg)
22.5°
22438
45
17
10
3800
152
90°
67.5°
5. Major Crown End(ii) Plumb Cut Offset Method
In a Right Angled Triangle one of the angles = 90°
![Page 147: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/147.jpg)
22.5°
22438
45
17
10
3800
152
90°
5. Major Crown End(ii) Plumb Cut Offset Method
The other 2 angles must = 90°(180° – 90° = 90°)
![Page 148: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/148.jpg)
22.5°
22438
45
17
10
3800
152
90°
5. Major Crown End(ii) Plumb Cut Offset Method
Therefore this angleMust = 90° - Roof Pitch
![Page 149: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/149.jpg)
22.5°
22438
45
17
10
3800
152
90°
67.5°
5. Major Crown End(ii) Plumb Cut Offset Method
Therefore this angle= 90° - 22.5°= 67.5°
![Page 150: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/150.jpg)
22.5°
22438
45
17
10
3800
152
90°
67.5°
5. Major Crown End(ii) Plumb Cut Offset Method
This Triangle is formed by the Roof
![Page 151: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/151.jpg)
22.5°
22438
45
17
10
3800
152
90°
67.5°
5. Major Crown End(ii) Plumb Cut Offset Method
A SIMILAR triangle is also formed in this position
![Page 152: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/152.jpg)
22.5°
22438
45
17
10
3800152
90°
67.5°
22.5°
22438
45
17
10
3800
152
90°
67.5°
5. Major Crown End(ii) Plumb Cut Offset Method
As the triangles are SIMILAR these angles must be the same
![Page 153: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/153.jpg)
22.5°
22438
45
17
10
3800
152
90°
67.5°
This Angle must = 90° - Roof Pitch = 67.5°
5. Major Crown End(ii) Plumb Cut Offset Method
![Page 154: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/154.jpg)
22438
45
17
10
152
67.5°
5. Major Crown End(ii) Plumb Cut Offset Method
This Angle must = 90° - Roof Pitch = 67.5°
![Page 155: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/155.jpg)
If we mark a square line at Top of Rafter & Extend Base
5. Major Crown End(ii) Plumb Cut Offset Method
22438
45
17
10
152
67.5°
![Page 156: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/156.jpg)
38
45
17
10
152
67.5°22.5°90.0°
A Triangle is Formed
5. Major Crown End(ii) Plumb Cut Offset Method
![Page 157: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/157.jpg)
38
45
17
10
152
67.5°22.5°90.0°
This angle is the same as the Roof Pitch
5. Major Crown End(ii) Plumb Cut Offset Method
![Page 158: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/158.jpg)
38
45
17
10
152
67.5°22.5°90.0°
This angle must be 90°
5. Major Crown End(ii) Plumb Cut Offset Method
![Page 159: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/159.jpg)
38
45
17
10
152
67.5°22.5°90.0°
This angle must be 90° - Roof Pitch
5. Major Crown End(ii) Plumb Cut Offset Method
![Page 160: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/160.jpg)
38
45
17
10
152
67.5°22.5°90.0°
This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter
5. Major Crown End(ii) Plumb Cut Offset Method
![Page 161: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/161.jpg)
38
45
17
10
152
67.5°22.5°90.0°
This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter
5. Major Crown End(ii) Plumb Cut Offset Method
1.082
22.5°
0.41
4
![Page 162: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/162.jpg)
38
45
17
10
152
67.5°22.5°90.0°
This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter
5. Major Crown End(ii) Plumb Cut Offset Method
1.082
22.5°
0.41
4
Therefore we can use the same multipliers to determine its dimensions
![Page 163: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/163.jpg)
38
45
17
10
152
67.5°22.5°
90.0°
This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter
5. Major Crown End(ii) Plumb Cut Offset Method
What is the Pitch angle of this triangle?
![Page 164: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/164.jpg)
38
45
17
10
152
67.5°22.5°
90.0°
This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter
5. Major Crown End(ii) Plumb Cut Offset Method
What is the Plan Length?
Pitch Angle = 22.5°
![Page 165: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/165.jpg)
38
45
17
10
152
67.5°22.5°
90.0°
This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter
5. Major Crown End(ii) Plumb Cut Offset Method
What is the Plan Length?
Pitch Angle = 22.5°
Plan Length = 152 + 38= 190
![Page 166: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/166.jpg)
38
45
17
10
152
67.5°22.5°
90.0°
This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter
5. Major Crown End(ii) Plumb Cut Offset Method
Offset = Rise Multiplier x Plan Length = 0.414 x 190 = 77mm
Pitch Angle = 22.5°
This length isSimilar toThe Rise
![Page 167: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/167.jpg)
Worked Example - 1
• Roof Pitch 22.5°• Timber Depth 190
= (Tan 22.5°) x 190= 0.414 x 190= 79mm
![Page 168: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/168.jpg)
• There 2 Formulas to Determine the Plumb
1.= Tan (Roof Pitch°) x Timber Depth or
2.= Rise per m of Rafter x Timber Depth
(The first formula is probably the easiest as the second formula gets complicated with hips)
5. Major Crown End(ii) Plumb Cut Offset Method
![Page 169: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/169.jpg)
Worked Example - 1
• Roof Pitch 22.5°• Timber Depth 190
= (Tan 22.5°) x 190= 0.414 x 190= 79mm
![Page 170: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/170.jpg)
Worked Example - 2
• Roof Pitch 22.5°• Timber Depth 190
= 0.414 x 190= 79mm
![Page 171: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/171.jpg)
• Pattern Rafter (90 x 45)90
5. Major Crown End(ii) Plumb Cut Offset Method
![Page 172: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/172.jpg)
• Pattern Rafter (90 x 45)1. Mark Square Line
90
5. Major Crown End(ii) Plumb Cut Offset Method
![Page 173: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/173.jpg)
• Pattern Rafter (90 x 45)1. Mark Square Line2. Determine Plumb Cut Offset and Mark Out
= 90 x Rise per 1m of Rafter in plan or 90 x (Tan 22.5°) = 90 x 0.414 = 37mm
90
37
5. Major Crown End(ii) Plumb Cut Offset Method
![Page 174: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/174.jpg)
• Pattern Rafter (90 x 45)1. Mark Square Line2. Determine Plumb Cut Offset and Mark Out
90 x 0.414= 37mm3. Mark Plumb Cut
90
Plumb Cut
5. Major Crown End(ii) Plumb Cut Offset Method
37
![Page 175: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/175.jpg)
Worked Example• Based on the pitch of 25°and using a 150mm Deep Rafter determine ,
Plumb Cut Offset- Major Crown End
= 190 x Rise per 1 metre of Rafter in plan= 0.414 x 190mm= 79mm
![Page 176: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/176.jpg)
Worked Example - Answer
![Page 177: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/177.jpg)
Confirmation of Learning
• Based on the pitch & Timber Width supplied by the Trainer determine ,
Plumb Cut Offset- Major Crown End
On the Supplied A4 sheet demonstrate the set out of the “Plumb Cut”
![Page 178: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/178.jpg)
Confirmation of Learning - Answer• Based on the pitch & Timber Width supplied by the
Trainer determine ,
Plumb Cut Offset- Major Crown End
On the Supplied A4 sheet demonstrate the set out of the “Plumb Cut”
Click on Spreadsheet below to generate Answers
Roof Pitch 25 °Timber Width 90
Offsett(mm) 42
![Page 179: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/179.jpg)
Minor Crown End Rafters join in a similar manner to a hip rafter
6.Minor Crown End Rafters
Major Crown End Rafter
Minor Crown End Rafter
![Page 180: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/180.jpg)
CE
NT
RE
ING
RA
FT
ER
MAJOR CROWN
MINOR CROW
N
MIN
OR CROW
N
CE
NT
RE
ING
RA
FT
ER
(6) Minor Crown End Rafters
Radius = ½ Span
Octagonal End Based on Semi Circle
(a) Centreline Length How Far does it Travel in plan?
![Page 181: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/181.jpg)
CE
NT
RE
ING
RA
FT
ER
MAJOR CROWN
MINOR CROW
N
MIN
OR CROW
N
CE
NT
RE
ING
RA
FT
ER
(6) Minor Crown End Rafters
Plan Length = ½ Span
Octagonal End Based on Semi Circle
Major Crown is a Radius
(a) Centreline Length How Far does it Travel in plan?
![Page 182: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/182.jpg)
CE
NT
RE
ING
RA
FT
ER
MAJOR CROWN
MINOR CROW
N
MIN
OR CROW
N
CE
NT
RE
ING
RA
FT
ER
(6) Minor Crown End RaftersPlan Length = ½ Span
Octagonal End Based on Semi Circle
Major Crown is a Radius
Minor Crown also is a Radius
(a) Centreline Length How Far does it Travel in plan?
![Page 183: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/183.jpg)
1/2
SP
AN
1/2 SPAN
RISE
1/2 SPAN
PLUMB CUT
ROOF PITCH1/2 SPAN
1/2
SPAN
(6) Minor Crown End Rafters
Plan Length = ½ Span
Minor Crown End Rafters travel to Gathering Point
(a) Centreline Length How Far does it Travel in plan?Plan Length = ½ Span
Mino
r Cro
wn End
Minor Crown End
![Page 184: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/184.jpg)
(6) Minor Crown End Rafters
Plan Length = ½ Span
1/2
SP
AN
1/2 SPAN
RISE
1/2 SPAN
PLUMB CUT
ROOF PITCH1/2 SPAN
1/2
SPAN
(a) Centreline Length Determine Centreline Length: Which Multiplier?
The Rise be same as1.Common Rafter &2.Major Crown End Rafter
Mino
r Cro
wn End
Minor Crown End
![Page 185: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/185.jpg)
(6) Minor Crown End Rafters
Plan Length = ½ Span
1/2
SP
AN
1/2 SPAN
RISE
1/2 SPAN
PLUMB CUT
ROOF PITCH1/2 SPAN
1/2
SPAN
(a) Centreline Length Determine Centreline Length: Which Multiplier?
The Rise be same asCommon Rafter &Major Crown End Rafter
The Plan Length is the same asCommon Rafter &Major Crown End Rafter
Mino
r Cro
wn End
Minor Crown End
![Page 186: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/186.jpg)
(6) Minor Crown End Rafters
Plan Length = ½ Span
1/2
SP
AN
1/2 SPAN
RISE
1/2 SPAN
PLUMB CUT
ROOF PITCH1/2 SPAN
1/2
SPAN
(a) Centreline Length Determine Centreline Length: Which Multiplier?
The Rise be same asCommon Rafter &Major Crown End Rafter
The Plan Length is the same asCommon Rafter &Major Crown End Rafter
The Pitch must be the same asCommon Rafter &Major Crown End Rafter
Mino
r Cro
wn End
Minor Crown End
![Page 187: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/187.jpg)
1/2
SP
AN
1/2 SPAN
RISE
1/2 SPAN
PLUMB CUT
ROOF PITCH1/2 SPAN
1/2
SPAN
(6) Minor Crown End Rafters(a) Centreline Length Determine Centreline Length: Which Multiplier?
The Rise be same asCommon Rafter &Major Crown End Rafter
The Plan Length is the same asCommon Rafter &Major Crown End Rafter
The Pitch must be the same asCommon Rafter &Major Crown End Rafter
Mino
r Cro
wn End
Minor Crown End
We use the Common Rafter Multiplier = Rafter Length per metre
![Page 188: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/188.jpg)
1m Triangle Multipliers
1.082
22.5°
0.41
4
1.159
20.9°
Common Rafter Multiplier
![Page 189: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/189.jpg)
CE
NT
RE
ING
RA
FT
ER
MAJOR CROWN
MINOR CROW
N
MIN
OR CROW
N
CE
NT
RE
ING
RA
FT
ER
(a) Centreline Length = Plan Length x Rafter Length per m
Note - Plan Length = ½ Span (Which is the same as the Major Crown)
(6) Minor Crown End Rafters
Plan Length = ½ Span
![Page 190: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/190.jpg)
Worked ExampleExercise 6a
• Determine Minor Crown End Centreline Length• Span = 7600• Pitch = 22.5°
Centreline Length = Plan Length x Rafter Length per m
Note – Plan Length = ½ Span
Centreline Length = 3800 x 1.082= 4112
![Page 191: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/191.jpg)
Confirmation of LearningExercise 6a
• Based on data given to you by you trainer determine,
True Length Minor Crown End Rafter
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Confirmation of Learning - AnswerExercise 6a
• Based on data given to you by you trainer determine,
Centreline Length Major CrownClick on Spread Sheet to determine answers
°
Centreline Length = 3800 x 1.082= 4113
SpanPitch
760022.5
![Page 193: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/193.jpg)
To Determine the True Length we must determine the reduction in length from the Centreline Length
This is called the Shortening
(6) Minor Crown End Rafters
Major Crown End Rafter
Minor Crown End Rafter
![Page 194: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/194.jpg)
There are 2 methods to determine the Shortening
I.MathematicallyII.Graphically
(6) Minor Crown End Rafters(b) Shortening
Minor Crown End Rafter
Major Crown End Rafter
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(b)(i) Shortening of Crown End Rafters from Centreline Length - Mathematically
Remember Centreline Plan Length = ½ Span
(6) Minor Crown End Rafters
Minor Crown End Rafter
Major Crown End Rafter
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(b)(i) Shortening of Crown End Rafters from Centreline Length - Mathematically
(6) Minor Crown End Rafters
1/2
SP
AN
1/2 SPAN
PLUMB CUT
ROOF PITCH1/2 SPAN
1/2
SPAN
MAJOR CROWN
MIN
OR CROW
N
MINOR CROW
NC
EN
TR
EIN
G R
AF
TE
RS
Rafter travels to Intersection of
•Centring Rafter &•Major Crown
![Page 197: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/197.jpg)
½ RAFTER
½ R
AF
TE
R
½ RAFTER x 1.414
(b)(i) Shortening of Crown End Rafters from Centreline Length - Mathematically
The Rafters Plan length is reduced by
√(½ Rafter2 + ½ Rafter2)
We know form our previous studyOf HIP ROOFS that this can be simplified to
½ Rafter x 1.414
(6) Minor Crown End Rafters
Major Crown End Rafter
Note 1.414 = √2
Minor Crown End Rafter
Shortening
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½ RAFTER
½ R
AF
TE
R
½ RAFTER x 1.414
(b)(i) Shortening of Crown End Rafters from Centreline Length - Mathematically
Shortening = ½ Rafter x 1.414
(6) Minor Crown End Rafters
Major Crown End Rafter
Shortening
Note 1.414 = √2
Minor Crown End Rafter
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½ RAFTER
½ R
AF
TE
R
½ RAFTER x 1.414
(b)(i) Shortening of Crown End Rafters from Centreline Length - Mathematically
Shortening = ½ Rafter x 1.414
Worked Example
Rafter = 35mm
Shortening = ½ Rafter x 1.414 = (35 ÷ 2) x 1.414 = 17 x 1.414 = 24mm
(6) Minor Crown End Rafters
Major Crown End Rafter
Shortening
Note 1.414 = √2
Minor Crown End Rafter
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Confirmation of Learning
• Determine the shortening of the Rafter Width nominated by your trainer.
• Note – this is a mathematical exercise and the width need not be an orderable width
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Confirmation of Learning - Answer
• Determine the shortening of the Rafter Width nominated by your trainer.
• Note – this is a mathematical exercise and the width need not be an orderable width.– Click On Spread sheet to generate answers
Timber Width (mm)
Shortening = x 1.414= ( 42 ÷ 2 ) x 1.414= x 1.414=
42
Width ÷ 2
2129.694
![Page 202: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/202.jpg)
½ RAFTER
½ R
AF
TE
R
½ RAFTER x 1.414
(b)(i) Shortening of Crown End Rafters from Centreline Length - Mathematically
Shortening = ½ Rafter x 1.414
Worked Example
Rafter = 35mm
Shortening = ½ Rafter x 1.414 = (35 ÷ 2) x 1.414 = 17 x 1.414 = 24mm
(6) Minor Crown End Rafters
Major Crown End Rafter
Shortening
Note 1.414 = √2
Minor Crown End Rafter
This is a relatively easy calculation if all Roof members are the same thickness
If the Centring & Major Crown Rafters are different thicknesses you should considerUsing the “Graphical Method”
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6. Minor Crown End Rafter(b)(ii) Shortening of Crown End Rafters - Graphically
•You should develop an understanding of this method
– It works on any Roof– It develops all bevels & shortenings– No formulas to remember only a method
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Gathering Point
CE
NT
RIN
G R
AF
TE
RS
MIN
OR CROW
N END R
AFTER
MINOR CROW
N END
MAJOR CROWN END RAFTER
Draw Centrelines
6. Minor Crown End Rafter(b)(ii) Shortening of Crown End Rafters - Graphically
![Page 205: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/205.jpg)
17.5
Gathering Point
CE
NT
RIN
G R
AF
TE
RS
MIN
OR CROW
N END R
AFTER
MINOR CROW
N END
MAJOR CROWN END RAFTER
Draw Timber Thicknesses at full size
In this case all Roof MembersAre 35mm thick
i.e. 17.5 either side of Centreline
6. Minor Crown End Rafter(b)(ii) Shortening of Crown End Rafters - Graphically
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Gathering Point
CE
NT
RIN
G R
AF
TE
RS
MIN
OR CROW
N END R
AFTER
MINOR CROW
N END
MAJOR CROWN END RAFTER
Dimension Shortening from Centreline
Note Zoomed in for Clarity
6. Minor Crown End Rafter(b)(ii) Shortening of Crown End Rafters - Graphically
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Gathering Point
CE
NT
RIN
G R
AF
TE
RS
MIN
OR CROW
N END R
AFTER
MINOR CROW
N END
MAJOR CROWN END RAFTER
To put this drawing into practical use you need to understand that
1.This is a TRUE representation of the actualIntersection of Roof members in PLAN
If we can transfer these dimension to our Rafter we can determine the True length and All required edge bevels
6. Minor Crown End Rafter(b)(ii) Shortening of Crown End Rafters - Graphically
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6. Minor Crown End Rafterb) ii. Shortening from Centreline Length - Graphically
Select a timber of Suitable Length to use as the Minor Crown Rafter
Side Elevation
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6. Minor Crown End Rafterb) ii. Shortening from Centreline Length - Graphically
Mark Out Centreline Length as determined in 6a
CENTRELINE LENGTH
22.5
°
Side Elevation
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6. Minor Crown End Rafterb) ii. Shortening from Centreline Length - Graphically
Mark Out Plumb Cuts as determined in 6c
CENTRELINE LENGTH
22.5
°
Side Elevation
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6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
Mark Lines square on Top of Rafter
CENTRELINE LENGTH
22.5
°
Side Elevation
![Page 212: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/212.jpg)
CENTRELINE LENGTH
22.5
°
6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
Isometric View
Centreline Length
You Rafter should now be marked with1.Centreline Length
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6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
CENTRELINE LENGTH
22.5
°
These lines are Plumb
Side Elevation
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6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
CENTRELINE LENGTH
22.5
°
90°
A line 90° to Plumb will be level
Side Elevation
![Page 215: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/215.jpg)
6. Minor Crown End Rafter) ii. Shortening from Centreline Length - Graphically
Mark Out Plumb Cuts as determined in 6c
CENTRELINE LENGTH
22.5
°
90°
The measurements on the drawingare in the level plane.
The set out must also be in the level plane
Side Elevation
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6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
Mark Out a level line approximately ½ way down the top plumb cut
CENTRELINE LENGTH
22.5
°
90°
Side Elevation
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6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
25
Transfer plan measurements determined in 6 (b) (ii)
Mark Centreline
Shortening Distance
Side Elevation
Plan View
All measurements are taken from Centreline Length
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6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
25
Transfer plan measurements determined in 6 (d) (ii)
Mark Line using Plumb Cut Bevel
Side Elevation
Plan View
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6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
25
Transfer plan measurements determined in 6 (d) (ii)
Mark Line using Plumb Cut Bevel
Which represents this point in PLAN
Side Elevation
Plan View
![Page 220: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/220.jpg)
6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
Mark Out Plumb Cuts as determined in 6c
25
90°
Isometric View
Mark Line square on Top of Rafter
Centreline Length
![Page 221: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/221.jpg)
6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
Mark Out Plumb Cuts as determined in 6c
25
90°
Isometric View
Mark Centreline
Centreline Length
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6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
42
25
Transfer plan measurements determined in 6 (d) (ii)
Mark Edge Bevel Shortening Distance
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6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
42
25
Transfer plan measurements determined in 6 (d) (ii)
Mark Line using Plumb Cut Bevel
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6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
42
25
Transfer plan measurements determined in 6 (d) (ii)
Mark Line using Plumb Cut Bevel
Which represents these points in PLAN
![Page 225: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/225.jpg)
6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
42
90°
Isometric View
Mark Lines square on Top of Rafter
Centreline Shortening
Centreline Length
![Page 226: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/226.jpg)
CENTRELINE LENGTH
22.5
°
25
42
6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
Isometric View
You Rafter should now be marked with1.Centreline Length2.Centreline Shortening3.Edge Bevel Shortening4.Thickness Centreline Mark
Thickness Centreline Mark
![Page 227: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/227.jpg)
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25
42
Isometric ViewPlan View
Centreline Length
6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
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6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
25
42
Isometric ViewPlan View
Centreline Length
Centreline Shortening
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6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
25
42
Isometric ViewPlan View
Centreline Length
Centreline Shortening
Edge Bevel Shortening
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6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
25
42
Isometric View
Thickness Centreline Mark
Plan View
Centreline Length
Centreline Shortening
Edge Bevel Shortening
![Page 231: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/231.jpg)
6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
CE
NT
RE
LIN
E L
EN
GT
H
CE
NT
RE
LIN
E S
HO
RT
EN
ING
ED
GE
BE
VE
L S
HO
RT
EN
ING
Isometric View
This is the Shape of theend of the Rafter in Plan
Plan View
![Page 232: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/232.jpg)
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6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
CE
NT
RE
LIN
E L
EN
GT
H
CE
NT
RE
LIN
E S
HO
RT
EN
ING
ED
GE
BE
VE
L S
HO
RT
EN
ING
Isometric View
This is the Shape of theEnd of the Rafter
It is based on the measurementsDetermined previously
Plan View
![Page 233: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/233.jpg)
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6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
CE
NT
RE
LIN
E L
EN
GT
H
CE
NT
RE
LIN
E S
HO
RT
EN
ING
ED
GE
BE
VE
L S
HO
RT
EN
ING
Isometric View
This is the Shape of theEnd of the Rafter
It is based on the measurementsDetermined previously
Plan View
We now replicate what we see in Plan on the Actual Rafter
![Page 234: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/234.jpg)
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6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
CE
NT
RE
LIN
E L
EN
GT
H
CE
NT
RE
LIN
E S
HO
RT
EN
ING
ED
GE
BE
VE
L S
HO
RT
EN
ING
Isometric View
This is the Shape of theEnd of the Rafter
It is based on the measurementsDetermined previously
Plan View
Draw Lines Starting From 1.Edge Bevel Shortening
![Page 235: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/235.jpg)
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6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
CE
NT
RE
LIN
E L
EN
GT
H
CE
NT
RE
LIN
E S
HO
RT
EN
ING
ED
GE
BE
VE
L S
HO
RT
EN
ING
Isometric View
This is the Shape of theEnd of the Rafter
It is based on the measurementsDetermined previously
Plan View
Draw Lines Starting From 1.Edge Bevel Shortening to Intersection of2.Centreline Shortening & Thickness Centreline to
![Page 236: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/236.jpg)
6. Minor Crown End Rafterd) ii. Shortening from Centreline Length - Graphically
CE
NT
RE
LIN
E L
EN
GT
H
CE
NT
RE
LIN
E S
HO
RT
EN
ING
ED
GE
BE
VE
L S
HO
RT
EN
ING
Isometric View
The Rafter is then cut to This Shape
The length has also been shortenedAnd ready to be installed
Mark Out Plumb Cuts as determined in 6cPlan View
![Page 237: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/237.jpg)
Confirmation of Learning
• Develop in Plan the Shortening of an Octagonal End Roof • Timber Widths to be supplied by Trainer is 45mm thick
•On Timber Supplied Develop required shortening based on a pitch of 27° & ½ Span of 300mm– Timber to be supplied by Trainer
![Page 238: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/238.jpg)
Confirmation of Learning - Answers
1. Develop in Plan the Shortening of an Octagonal End Roof
a) Timber Widths to be supplied by Trainer is 45mm thick
Submission should be as Answer 12.On Timber Supplied Develop shortening based on a pitch of 27° & ½ Span of 300mmb) Timber to be supplied by Trainer
![Page 239: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/239.jpg)
Confirmation of Learning – Answer 1
• Shortening in Plan
32
54
54
![Page 240: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/240.jpg)
Confirmation of Learning – Answer 2
• Shortening in Elevation
CENTERLINE LENGTH = 337MM
27°
32
54
ED
GE
BE
VE
L S
HO
RT
EN
ING
CE
NT
RE
LIN
E S
HO
RT
EN
ING
CE
NT
RE
LIN
E L
EN
GT
H
![Page 241: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/241.jpg)
(c) True Length
(6) Minor Crown End Rafters
1/2
SP
AN
1/2 SPAN
½ SPAN – (½
RAFTER x 1.414)
PLUMB CUT
ROOF PITCH1/2 SPAN
1/2
SPAN
MAJOR CROWN
MIN
OR CROW
N
MINOR CROW
NC
EN
TR
EIN
G R
AF
TE
RS
Rafter travels to Intersection of
•Centring Rafter &•Major Crown
![Page 242: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/242.jpg)
½ RAFTER
½ R
AF
TE
R
½ RAFTER x 1.414
(c) True Length
How far does it travel in plan?
Remember Centreline Plan Length = ½ SpanTrue Length in Plan = ½ Span – ½ Rafter x 1.414
(6) Minor Crown End Rafters
Rafter Plan Reduction
Major Crown End Rafter
Minor Crown End Rafter
![Page 243: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/243.jpg)
45,0
°(½ Span – (½
Rafter x 1.414)) x Rafter Length per m
(b) True Length = Plan Length x Rafter Length per m
Note – Plan Length = (½ Span – Shortening)) or = (½ Span – (½ Rafter x 1.414))
(6) Minor Crown End Rafters
![Page 244: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/244.jpg)
Worked Example
• Minor Crown True Length =– Plan Length x Rafter Length per m– Plan Length = (½ Span – ½ Rafter x 1.414)
= (3800 –(35 ÷ 2) x 1.414) x 1.082= (3800 – 17.5 x 1.414) x 1.082= (3800 – 25) x 1.082= 3775 x 1.082= 4085
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Confirmation of Learning• Determine the True Length of the Minor
Crown End Rafter based on data given to you by the Trainer.– Span To be Supplied by Trainer– Pitch To be Supplied by Trainer– Timber Width To be Supplied by Trainer
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Confirmation of Learning - Answer• Determine the True Length of the Minor
Crown End Rafter based on data given to you by the Trainer.– Span To be Supplied by Trainer– Pitch To be Supplied by Trainer– Timber Width To be Supplied by Trainer Click on Spread Sheet to check answers
Timber Width (mm)Span (mm)Pitch°Rafter per m
Shortening = x= ( 35 ÷ 2) x 1.414= 17.5 x=
Note Plan Length = 1/2 Span - ShorteningTrue Length = x Rafte Length per m
= ( 3800 - 25 ) x = 3775 x= 4086
35
24.745
1.08222.57600
Plan Length
Width ÷ 2 1.414
1.414
1.0821.082
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(c) Plumb Cut Minor Crown
As we use the Common Rafter multiplier we can use the Common Rafter Plumb CutThe following slides demonstrate how to develop the plumb cut
(6) Minor Crown End Rafters
1/2
SP
AN
1/2 SPAN
1/2 SPAN
1/2
SPAN
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(c) Plumb Cut Minor Crowni. Graphically
(6) Minor Crown End Rafters
1/2
SP
AN
1/2 SPAN
1/2 SPAN
1/2
SPAN
Extend Construction LinesPerpendicular to ends of Rafter
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(c) Plumb Cut Minor Crowni. Graphically
(6) Minor Crown End Rafters
1/2
SP
AN
1/2 SPAN
1/2 SPAN
1/2
SPAN
Establish False Top Plate
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(c) Plumb Cut Minor Crowni. Graphically
(6) Minor Crown End Rafters
1/2
SP
AN
1/2 SPAN
1/2 SPAN
1/2 SPAN
1/2
SPAN
Establish Plan Length
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(c) Plumb Cut Minor Crowni. Graphically
(6) Minor Crown End Rafters
1/2
SP
AN
1/2 SPAN
RISE
1/2 SPAN
1/2 SPAN
1/2
SPAN
Establish Rise
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(c) Plumb Cut Minor Crowni. Graphically
(6) Minor Crown End Rafters
1/2
SP
AN
1/2 SPAN
RISE
1/2 SPAN
PLUMB CUT
ROOF PITCH1/2 SPAN
1/2
SPAN
Draw in Rafter•Establish Plumb Cut•Establish Roof Pitch
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Confirmation of Learning
• Using your previous drafting exercise determine graphically,
Plumb Cut - Minor Crown End
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1/2
SP
AN
MAJOR CROWN
MINOR CROW
N
MIN
OR CROW
N
45°
6. Minor Crown End Rafters(e) Edge Bevel Development
In Plan this Angle = 45⁰
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1/2
SP
AN
MAJOR CROWN
MINOR CROW
N
MIN
OR CROW
N
45°
6. Minor Crown End Rafters(e) Edge Bevel Development
In Plan this Angle = 45⁰
When can you use the plan angle?
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1/2
SP
AN
MAJOR CROWN
MINOR CROW
N
MIN
OR CROW
N
45°
6. Minor Crown End Rafters(e) Edge Bevel Development
In Plan this Angle = 45⁰
When can you use the plan angle?
When you use a power tool such as1.Drop Saw2.Power Saw etc
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Edge Bevel Minor Crown End RaftersPlan Angle
Plan Angle = 45⁰
Plan Angle = 90⁰
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Edge Bevel Minor Crown End RaftersPlan Angle
Plan Angle = 45⁰
Plan Angle = 90⁰
Both Sides MustBe Equal
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Edge Bevel Minor Crown End RaftersPlan Angle
Plan Angle = 45⁰
Plan Angle = 90⁰
Both Sides MustBe Equal
When Can You Use The Plan For the Edge Bevel ?
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Edge Bevel Minor Crown End RaftersPlan Angle
Plan Angle = 45⁰
Plan Angle = 90⁰
Both Sides MustBe Equal
When Can You Use The Plan For the Edge Bevel ?
1/2
SP
AN
MAJOR CROWN
MINOR CROW
N
MIN
OR CROW
N
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Minor Crown True Angle
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Minor Crown True Angle
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Minor Crown True Angle
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Minor Crown True Angle
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Minor Crown True Angle
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Minor Crown True Angle
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Minor Crown True Angle
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Minor Crown True Angle
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Edge Bevel Minor Crown End RaftersTrue Angle
What members form the triangle?
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Edge Bevel Minor Crown End RaftersTrue Angle
What members form the triangle?
Centreline Length Rafter
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Edge Bevel Minor Crown End RaftersTrue Angle
What members form the triangle?
Centreline Length Rafter
If this angle is 45⁰
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Edge Bevel Minor Crown End RaftersTrue Angle
What members form the triangle?
Centreline Length Rafter
This angle must 45⁰
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Edge Bevel Minor Crown End RaftersTrue Angle
What members form the triangle?
Centreline Length Rafter
Both these sides must be equal
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Edge Bevel Minor Crown End RaftersTrue Angle
What members form the triangle?
Centreline Length Rafter
This line runs parallel with the top Of the Rafter
Which is level
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The Octagonal Roof is a geometric shape
No matter the size the angles are always the same
7.Plan Length Hip Rafter
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The Octagonal Roof is a geometric shape
No matter the size the angles are always the same
7. Plan Length Hip Rafter
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The Octagonal Roof is a geometric shape
No matter the size the angles are always the same
7.Plan Length Hip Rafter
These angles are always 90⁰
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The Octagonal Roof is a geometric shape
No matter the size the angles are always the same
7.Plan Length Hip Rafter
These angles are always 45⁰
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The Octagonal Roof is a geometric shape
No matter the size the angles are always the same
7.Plan Length Hip Rafter
These angles are always 22.5⁰
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These relationships are constant on all properly built Octagonal Roofs
7.Plan Length Hip Rafter
These angles are always 22.5⁰
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Calculate Plan Length of Hip
Plan Hip Length = ½ Span ÷ cos 22.5⁰ = ½ Span ÷ 0.924 = 1.082 (That it is equal to the Rafter Multiplier is a coincidence in this case)
7.Plan Length Hip Rafter
This is a fixed relationshipRegardless of pitch
MAJOR CROWN
½ SPAN - ½ Rafter
½ S
PA
N
1/2 Span x 1.082
22.5
°
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Calculate Plan Length of Hip
Simple Rule
Plan Hip Length = ½ Span x 1.082 (That it is equal to the Rafter Multiplier is a coincidence)
7.Plan Length Hip Rafter
This is a fixed relationshipRegardless of pitch
MAJOR CROWN
½ SPAN - ½ Rafter
½ S
PA
N
1/2 Span x 1.082
22.5
°
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Worked Example7. Plan Length of Hip
• Determine Plan Length of Hip– Span 7600
Plan Length = ½ Span x 1.082= (7600 ÷ 2) x 1.082= 3800 x 1.082= 4112
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1m Triangle Multipliers
1.082
22.5°
0.41
4
1.159
20.9°
Hip Rafter Multiplier
When we solved the 1m Triangle we developed the Hip Multiplier
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8.Centerline Length of Hip Rafter
As with all Roof members to determine the length we 1.Determine how far it travels in plan2.Apply the multiplier
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8.Centerline Length of Hip Rafter
As with all Roof members to determine the length we 1.Determine how far it travels in plan ?2.Apply the multiplier
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1m Triangle Multipliers
1.082
22.5°
0.41
4
1.159
20.9°
Hip Rafter Multiplier
If we remember our multiplier is derived on the following premise
Hip Rafter Length for every 1m metre of Rafter in Plan
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1m Triangle Multipliers
1.082
22.5°
0.41
4
1.159
20.9°
Hip Rafter Multiplier
If we remember our multiplier is derived on the following premise
Hip Rafter Length for every 1m metre of Rafter in Plan
It is the Plan Length of the Rafter that we must determine!
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8.Centerline Length of Hip Rafter
How far does the Rafter Travel in plan to intersect the Hip in plan?
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8.Centerline Length of Hip Rafter
How far does the Rafter Travel in plan to intersect the Hip in plan?
The Rafter travels ½ Span
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8.Centerline Length of Hip Rafter
How far does the Rafter Travel in plan to intersect the Hip in plan?
The Rafter travels ½ Span
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8.Centerline Length of Hip Rafter
As with all Roof members to determine the length we 1.Determine how far it travels in plan = ½ Span2.Apply the multiplier
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8.Centerline Length of Hip Rafter
As with all Roof members to determine the length we 1.Determine how far it travels in plan = ½ Span2.Apply the multiplier
![Page 294: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/294.jpg)
1m Triangle Multipliers
1.082
22.5°
0.41
4
1.159
20.9°
Hip Rafter Multiplier
Hip Rafter Multiplier for 22.5° = 1.159
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8.Centerline Length of Hip Rafter
As with all Roof members to determine the length we 1.Determine how far it travels in plan = ½ Span2.Apply the multiplier = As per 1m triangle multiplier
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8.Centerline Length of Hip Rafter
Centreline Length of Hip = Plan Length x Hip Rafter Length per mNote - Plan Length = ½ Span
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Worked Example• Determine Centreline length of Hip Rafter
– Span 7600mm– Pitch 22.5°– Hip Multiplier 1.159
Centreline Length of Hip = Plan Length x Hip Rafter Length per mNote - Plan Length = ½ Span
= (7800 ÷ 2) x 1.159= 3800 x 1.159= 4404
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Confirmation of Learning• Determine Centreline length of Hip Rafter
– Span Supplied by Trainer– Pitch Supplied by Trainer– Hip Multiplier As derived from pitch
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Confirmation of Learning - Answer• Determine Centreline length of Hip Rafter
– Span Supplied by Trainer– Pitch Supplied by Trainer– Hip Multiplier As derived from pitchClick on Spread Sheet for Answers
SpanPitch °Hip Multiplier
Hip Centreline = 3800 x 1.159= 4404
22.57600
1.159
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9. Hip Plumb Cut
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9a.Hip Plumb - Graphically
Draw in False Top Plate
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9a.Hip Plumb - Graphically
Establish Rise of RoofBy drawing in Common Rafter
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9a.Hip Plumb - Graphically
Draw in Ridge Line
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9a.Hip Plumb - Graphically
Rotate Length of Hip onto Ridge
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9a.Hip Plumb - Graphically
Extend this length up to false Top Plate
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9a.Hip Plumb - Graphically
Establish the rise The Rise will be the same as theCommon Rafter Rise
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9a.Hip Plumb - Graphically
Draw in Hip Rafter
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9a.Hip Plumb - Graphically
Plumb Cut Hip
Plumb Cut as Shown
![Page 309: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/309.jpg)
Confirmation of Learning
• Using the A3 drawing previously developed using the method outlined
• Develop Plumb Cut - Graphically
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Confirmation of Learning - Answer
• Using the A3 drawing previously developed using the method outlined
• Develop Plumb Cut – Graphically• Click on Spread Sheet to determine Hip pitch
based on Common Rafter Pitch, Using Pitching template on next slide to confirm
Roof Pitch 25 °Hip Pitch 23.3 °
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15°
20°
25°30°
35°Answer Drawing 1 – Click on Drawing to Open File
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9b.Hip Plumb – Steel Square Method
Rise
Hip Run
Hip Plumb Cut
1.082
22.5°
0.41
4
1.159
20.9°
Reduce Hip Triangle to Steel Square
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9b.Hip Plumb – Steel Square Method
Rise
Hip Run
Hip Plumb Cut
1.082
22.5°
0.41
4
1.159
20.9°
Reduce Hip Triangle to Steel SquareDivide by 2
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9b.Hip Plumb – Steel Square Method
Rise
Hip Run
Hip Plumb Cut
1.082
22.5°
0.41
4
1.159
20.9°
Reduce Hip Triangle to Steel SquareDivide by 2
Rise = 207Hip Run = 541
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9b.Hip Plumb – Steel Square Method
207
541
Hip Plumb Cut
1.082
22.5°
0.41
4
1.159
20.9°
Reduce Hip Triangle to Steel SquareDivide by 2
Rise = 207Hip Run = 541
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9b.Hip Plumb – Offset Method
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9b.Hip Plumb – Offset Method
1.082
22.5°
0.41
4
1.159
20.9°
Common Rafter Multiplier
Plumb Cut Offset = Tan(Hip Pitch°) x Timber Depth or= (Timber Depth ÷ 1.082) x Rise
![Page 318: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/318.jpg)
Worked Example 1Using Derived Hip Pitch
Roof Pitch = 22.5Hip Pitch = 20.9°Timber Depth = 190mm
= (Tan 20.9°) x Timber Depth= 0.382 x 190= 73mm
![Page 319: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/319.jpg)
Worked Example 2Using 1m Trainagle Data
Roof Pitch = 22.5Rise = 0.414Timber Depth = 190mm
= (Timber Depth ÷ 1.082) x 0.414= (190 ÷ 1.082) x 0.414= 175.6 x 0.414= 73mm
![Page 320: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/320.jpg)
10. True Length Hip Rafter
Cen
trei
ng R
afte
r
MAJOR CROWN
HIP RAFTERM
INOR CROWN
HIP
RA
FT
ER
HIP RAFTER
MIN
OR CROW
N
HIP
RA
FT
ER
To determine the True Length 1.Determine how far it travels 2.Apply the correct multiplier
![Page 321: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/321.jpg)
10 True Length Hip Raftera) Shortening
HIP RAFTERM
INOR CROWN
HIP
RA
FT
ER
PLA
N L
EN
GT
H
To determine the True Length 1.Determine how far it travels2.Apply the correct multiplier
We must determine howFar in the direction of the Rafter does the hip travel
![Page 322: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/322.jpg)
9. True Length Hip Raftera) Shortening
HIP RAFTERM
INOR CROWN
HIP
RA
FT
ER
PLA
N L
EN
GT
H
1/2
SP
AN
To determine the True Length 1.Determine how far it travels2.Apply the correct multiplier
We must determine theDistance from ½ Span to The plan length
This is called the shortening
![Page 323: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/323.jpg)
HIP RAFTERM
INOR CROWN
HIP
RA
FT
ER
PLA
N L
EN
GT
H
1/2
SP
AN
½ R
IDG
E
9. True Length Hip Raftera) Shortening
To determine the True Length 1.Determine how far it travels2.Apply the correct multiplier
We Reduce from ½ Span1.½ Ridge Thickness
![Page 324: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/324.jpg)
9. True Length Hip Raftera) Shortening
HIP RAFTERM
INOR CROWN
HIP
RA
FT
ER
PLA
N L
EN
GT
H
1/2
SP
AN
½ R
IDG
E
½ R
AF
TE
R x
1.4
14
To determine the True Length 1.Determine how far it travels2.Apply the correct multiplier
We Reduce from ½ Span1.½ Ridge Thickness2.½ Rafter x 1.414
![Page 325: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/325.jpg)
9. True Length Hip Raftera) Shortening
HIP RAFTERM
INOR CROWN
HIP
RA
FT
ER
PLA
N L
EN
GT
H
1/2
SP
AN
½ R
IDG
E
½ R
AF
TE
R x
1.4
14
To determine the True Length 1.Determine how far it travels2.Apply the correct multiplier
We Reduce from ½ Span1.½ Ridge Thickness2.½ Rafter x 1.414
This Reduction is call the Shortening
= ½ Ridge Thickness + ½ Rafter x 1.414
![Page 326: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/326.jpg)
9. True Length Hip Raftera) Shortening – Worked Example
HIP RAFTERM
INOR CROWN
HIP
RA
FT
ER
PLA
N L
EN
GT
H
1/2
SP
AN
½ R
IDG
E
½ R
AF
TE
R x
1.4
14
To determine the True Length 1.Determine how far it travels2.Apply the correct multiplier
All members 35mm= ½ Ridge Thickness + (½ Rafter x 1.414)= 17.5 + (17.5 x 1.414)= 17.5 + 25= 42.5mm
![Page 327: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/327.jpg)
Conformation of Learning
• Based on Data given to you by the Trainer– Ridge Thickness Supplied by Trainer– Rafter Thickness Supplied by Trainer
• Determine the Shortening
![Page 328: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/328.jpg)
9. True Length Hip Raftera (i) Edge Bevel – Graphically
This Dimension measured from True Length in Plan
ED
GE
BE
VE
L SH
OR
TEN
ING
![Page 329: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/329.jpg)
TR
UE
LE
NG
TH
Isometric Elevation
9. True Length Hip Raftera (iii) Edge Bevel – Graphically
![Page 330: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/330.jpg)
TR
UE
LE
NG
TH
ED
GE
BE
VE
L S
HO
RT
EN
ING
EDGE BEVEL SHORTENING
Isometric Elevation
This measurementIs at 90° to the Plumb Cut
9. True Length Hip Raftera (iii) Edge Bevel – Graphically
![Page 331: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/331.jpg)
TR
UE
LE
NG
TH
ED
GE
BE
VE
L S
HO
RT
EN
ING
EDGE BEVEL SHORTENING
Isometric Elevation
Develop Edge Bevel
9. True Length Hip Raftera (iii) Edge Bevel – Graphically
![Page 332: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/332.jpg)
Confirmation of Learning
• On Page xx develop the edge bevel graphically
• With Timber Supplied– Mark Plumb Cut– Mark Centreline Shortening– Mark Edge Bevels
![Page 333: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/333.jpg)
Confirmation of Learning - Answer
• On Page xx develop the edge bevel graphically– Pitch– Span
• With Timber Supplied– Mark Centreline Length– Mark Plumb Cut– Mark Centreline Shortening– Mark Edge Bevels
Pitch 22.5Span (mm) 7600Rafter Thickness (mm) 35Hip Thickness (mm) 35Centreline Length (mm) 4404
Shortening in Plan 45.7297Edge Bevel in Plan 42.24874
All measurements from Centreline Length
![Page 334: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/334.jpg)
9. True Length Hip Rafter(b) True Plan Length
HIP RAFTERM
INOR CROWN
HIP
RA
FT
ER
PLA
N L
EN
GT
H
1/2
SP
AN
½ R
IDG
E
½ R
AF
TE
R x
1.4
14
To determine the True Length 1.Determine how far it travels2.Apply the correct multiplier
Determine Plan Length= ½ Span - Shortening
![Page 335: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/335.jpg)
9. True Length Hip Rafter(b) True Plan Length – Worked Example
HIP RAFTERM
INOR CROWN
HIP
RA
FT
ER
PLA
N L
EN
GT
H
1/2
SP
AN
½ R
IDG
E
½ R
AF
TE
R x
1.4
14
To determine the True Length 1.Determine how far it travels2.Apply the correct multiplier
Determine Plan Length= ½ Span – Shortening= 3800 – 42.5= 3757.5
![Page 336: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/336.jpg)
Confirmation of Learning
• Based on the previous exercise and data supplied by the Trainer– Span Supplied by Trainer
• Determine True Plan Length Hip Rafter
![Page 337: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/337.jpg)
SH
OR
TE
NIN
G
ED
GE
BE
VE
L SH
OR
TE
NIN
G
9. True Length Hip Rafterc Develop Rafter Graphically
It is possible to not bother with the mathsAnd develop from the centreline length all measurements.
This is the easiest method for complex roof
![Page 338: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/338.jpg)
9. Minor Crown End Rafterc) Shortening from Centreline Length - Graphically
90°
Isometric View
Mark Lines square on Top of Rafter
Centreline Shortening
Centreline Length
![Page 339: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/339.jpg)
9. True Length Hip Rafter(b) True Plan Length
HIP RAFTERM
INOR CROWN
HIP
RA
FT
ER
PLA
N L
EN
GT
H
1/2
SP
AN
½ R
IDG
E
½ R
AF
TE
R x
1.4
14
To determine the True Length 1.Determine how far it travels2.Apply the correct multiplier
Determine Plan Length
![Page 340: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/340.jpg)
Confirmation of Learning
• On the Supplied sheet of Paper– Draw the shortening & edge bevels for the hip
– On the supplied piece of Timber based on data given to you by your trainer mark out a Hip Rafter Completely
- Using Any Method
![Page 341: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/341.jpg)
Confirmation of Learning
• On the Supplied sheet of Paper– Draw the shortening & edge bevels for the hip
– On the supplied piece of Timber based on data given to you by your trainer mark out a Hip Rafter Completely
![Page 342: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/342.jpg)
9. True Length Hip Rafter(b) True Length
HIP RAFTERM
INOR CROWN
HIP
RA
FT
ER
PLA
N L
EN
GT
H
1/2
SP
AN
½ R
IDG
E
½ R
AF
TE
R x
1.4
14
To determine the True Length 1.Determine how far it travels2.Apply the correct multiplier
Apply Multiplier= Plan Length x Hip per 1m Rafter
![Page 343: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/343.jpg)
9. True Length Hip Rafter(b) True Length – Worked Example
HIP RAFTERM
INOR CROWN
HIP
RA
FT
ER
PLA
N L
EN
GT
H
1/2
SP
AN
½ R
IDG
E
½ R
AF
TE
R x
1.4
14
To determine the True Length 1.Determine how far it travels2.Apply the correct multiplier
Apply Multiplier= Plan Length x Hip per 1m Rafter= 3757.5 x 1.159= 4355
![Page 344: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/344.jpg)
Confirmation of Learning
• Based on the previous exercises determine
• True Length Hip Rafter
![Page 345: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/345.jpg)
Creepers
1. Determine Creeper Shortening
2. Determine Long Point Correction
3. Determine 1st Creeper True Length
4. Determine all other Creepers
![Page 346: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/346.jpg)
Determine Shortening
These 2 Triangles are similar
![Page 347: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/347.jpg)
Determine Shortening
The Ratio between theSides must be equal
![Page 348: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/348.jpg)
Determine Shortening
Plan Shortening = ½ Span Spacing CL to End
![Page 349: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/349.jpg)
Determine Shortening
Plan Shortening = 1.000 200 0.414
For an Octagonal RoofThese are always the same
![Page 350: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/350.jpg)
Determine Shortening
Plan Shortening = 2.414 200
![Page 351: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/351.jpg)
Determine Shortening
Plan Shortening = 2.414 x 200
![Page 352: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/352.jpg)
Creepersa) Shortening
• Creeper Shortening• = (Spacing x 2.414) x Rafter Length /m
![Page 353: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/353.jpg)
Creepersa) Shortening – Worked Example
• Creeper Shortening– Pitch 22.5°– Spacing = 450mm
• = (Spacing x 2.414) x Rafter Length /m• = (450 x 2.414) x 1.082• = 1086.3 x 1.082• = 1175
![Page 354: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/354.jpg)
Creepersa) Shortening –at Confirmation of Learning
• Determine Creeper Shortening– Pitch Specified by Trainer– Spacing Specified by Trainer
![Page 355: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/355.jpg)
Creepers - Answera) Shortening –at Confirmation of Learning
• Determine Creeper Shortening– Pitch Specified by Trainer– Spacing Specified by Trainer
![Page 356: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/356.jpg)
Creepers
1. Determine Creeper Shortening
2. Determine Long Point Correction
3. Determine 1st Creeper True Length
4. Determine all other Creepers
![Page 357: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/357.jpg)
Creepersa) Long Point Correction in plan
3
The simplest way is to draw it
This can be done mathematically butIt is a convoluted process
In this the correction is -3mm
![Page 358: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/358.jpg)
Creepersa) Long Point Correction in plan
3
The simplest way is to draw it
This can be done mathematically butIt is a convoluted process
In this the correction is -3mm
![Page 359: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/359.jpg)
22.5
°
Creepersa) Long Point Correction in plan – Confirmation of Learning
On an A3 SheetDraw the intersection Of the member &Determine the Long PointCorrection
![Page 360: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/360.jpg)
22.5
°
Creepers - Answera) Long Point Correction in plan – Confirmation of Learning
On an A3 SheetDraw the intersection Of the member &Determine the Long PointCorrection
Hip Thickness 35Rafter Thickness 35
centerline short 45.7297Long Point Extenstion 42.24874
Long Point Correction -3.48097
![Page 361: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/361.jpg)
Creepers
1. Determine Creeper Shortening
2. Determine Long Point Correction
3. Determine 1st Creeper True Length
4. Determine all other Creepers
![Page 362: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/362.jpg)
Creepers(c) 1st Creeper
• = (½ Span + Correction) x Rafter per/m – Creeper Shortening
• = (3800 -3) x 1.082 – 1175• = 3797 x 1.082 – 1175• = 4108 – 1175• = 2933
![Page 363: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/363.jpg)
Creepers
1. Determine Creeper Shortening
2. Determine Long Point Correction
3. Determine 1st Creeper True Length
4. Determine all other Creepers
![Page 364: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/364.jpg)
Creepers(d) Determine Creepers
• = Previous Creeper – Creeper Shortening• = 2933 – 1175• = 1758 – 1175• = 583
![Page 365: Octagonal end roof](https://reader038.fdocuments.net/reader038/viewer/2022102905/55d01c1cbb61eb9d5d8b469d/html5/thumbnails/365.jpg)
Creepers(d) Determine Creepers
84