HIP ROOFS

Created BY Michael Martin July 2004 / revised may 2007 / reviewed & updated March 2010

Hip & Valley Roofs – P. 3

“4 Basic Principles” All ridges must be level & parallel to

wall plates All rafters must be placed at 90° to

wall plates – regardless of the roof shape

All hip and valleys must bisect the angle of the corner

Roof members are set out on centre lines

Components – P. 12

Wall plate Ridge Centering rafter Crown end Hip Common rafters Creepers Purlin Etc.

1 Ridge board (Major roof) 9 Crown-end rafter

2 Collar tie 10 Creeper rafter3 Common rafter 11 Valley rafter4 Centring rafter 12 Ridge board (Minor roof)5 Top plate 13 Common rafter (Minor roof)6 Fascia 14 Valley creeper rafter7 Hip rafter 15 Valley cripple creeper8 Purlin 16 Trimmer for minor ridge fixing

Set out – all relates to center lines

Centring rafter

RidgeCrown end rafter

Hip

Centering rafter

Ridge

Centeringrafter

Crown end rafter

New Members – summary to complete workbook section

Hip – Inclined member from wall plate at external corner to end of ridge

Crown end rafter – special rafter running from wall plate (center span position) to end of ridge

Creeper rafter – rafter cut in length to join hip

Set out

Ceiling frame also depends on set out of rafters

Set out as opposite

Textbook reference – P. 52

Ceiling joists

Set out ofrafters

Half spanH

alf s

pan

Set

out

of

rafte

rs

The Ridge for a hipped roof

Length = length of the building – width of building + rafter width

Pattern Rafters – P. 26

Now include Common / centering Crown end rafter Creeper rafters

Pattern Rafters

Remember Common / centering – reduce by ½

thickness of ridge Crown End – reduce by ½ thickness of

common rafter / centring rafter Creepers – are calculated on pattern –

by determining long point

Long point for 1st Creeper

Half thickness of Common Rafter

RIDGE

Spacing

CROWN END RAFTER

Half mitre thickness of Hip

CROWN END RAFTERRIDGE

Half thickness Common rafter

Half mitre thickness hip

1st Creeper

Spacing

Hip

CE

NT

RIN

G R

AF

TE

R

Determining long point of creeper – P. 25

1st mark out spacing from centre line

2nd take off half mitre thickness of hip

3rd add on half thickness of common rafter

You now have long point Continue to mark out other

creepers Look at next slide

Long point for 1st Creeper

Half thickness of Common Rafter

RIDGE

Spacing

CROWN END RAFTER

Half mitre thickness of Hip

CROWN END RAFTERRIDGE

Half thickness Common rafter

Half mitre thickness hip

1st Creeper

Spacing

Hip

CE

NT

RIN

G R

AF

TE

R

Bevels for the Hip Roof

Bevels – common rafters & centering rafters – P. 37

Rise

½ span

Plumb bevel

Level bevel

Bevels - hips

Create another triangle in the roof

Rise

Plan length hip

Plumb bevel

Level bevel

Bevels - hip

Relate to true length per metre again

As you do for common rafter

Bevels – hip (eg) 30° pitch

Rise per m run – tan 30° = .577

Use Pythagoras to create plan length of hip

√1.0² + 1.0² = 1.414 (plan length of hip)

True length per 1.414 run

√1.414² + .577² = 1.527

Bevels - hip

You have now created that new triangle

You can reduce this to fit steel square

Take bevels from this

Rise

.577

Plan length hip

1.414

True length 1.527

Bevels

You now have your first four bevels› Plumb bevel common rafter› Level bevel common rafter› Plumb bevel hip› Level bevel hip

In a hipped roof, there are eight (8) bevels all up – plumb bevel common rafter, level bevel common rafter, plumb bevel hip, level bevel hip, edge bevel hip, edge bevel creeper, face bevel purlin & edge bevel purlin

Bevels

These 8 bevels can be developed in a number of ways

Eventually you’ll choose which one that suits you› Geometric (we will draw ourselves)› Steel square › Direct method › Or combined triangles (not in text)

We will cover each one separately, one by one later

One Examplesteel square – P. 46

Main Roof Components

1st lets concentrate on what we know› Common

rafters› Centering

rafters› Hips› Creepers› ridge

What we’ve done already

Common rafters – set out on pattern

Crown end rafters – set out on pattern

Creepers – set out on pattern

Hips – we need to look at further

Hip rafters

Before you erect hip

You have to take into account

Reductions Ref: P16

Hips

1st at the ridge the hip must be reduced in length

You can calculate it or

Measure it in place In principle it is

reduced as shown opposite

Hand out – shortening at “x”

Hips

2nd at the birdsmouth you must reduce as well

Calculations of length give you position at outside of plate

Typically you cut corner to give better seating

Therefore birdsmouth must be reduced to suit

Handout – shortening at “y”

Hips

Set-out of birdsmouth on hip

Top of rafters, including hips, must be on the one plane

Set out of hip birdsmouth as opposite

See handout

Hipped Roof

Now you can build the main structure of the roof

Edge bevels for creepers and hips we’ll show you in workshop

Purlins we’ll look at after we develop other bevels

Drawing boards next week