ROOF TRUSS DESIGNS - IDEALS

ROOF TRUSS DESIGNS

FOR STANDARD AND SPECIAL CONDITIONS

1-lillard J. \vorth

Raymon H. Harrell

A reprint o£ papers presented at the Seventh Annual Short Course in Residential Construction sponsored by the University of Illinois Small Homes Council and the Division of University Extension, January 16-17, 1952.

Reprinted from "Seventh Annual Short Course in Residential Construction," copyrighted 1952 by the Small Homes Council, University of Illinois. All rights reserved. No part of this book may be reproduced in any form without permission in writing from the publishers.

Price: 25 cents

DESIGN OF ROOF TRUSSES

Willard J. Worth Research Assistant, Small Hames Council

Economy is one of the most important things in building today. That much I think we all agree on. That may well be the last thing we'll agree on. With each of you operating in different communities and each having local problems, it would be foolish to lay down a series of absolute statements. The best we can do is to tell you what we do know about trusses--you can judge for yourselves how important it is to you in your own set-up.

Truss Economy

Trusses for small homes are not new, and a good many people besides ourselves have been and still are interested in them. It is important to remember that economies are gained both in the savings of trusses over rafters and in the elimination of bearing partitions and their supporting constructions. It is probable that any other system of "clear span" framing would give equal savings. Right now, the best way we know to get . "clear spa.nn framing is through the use of trusses.

The Design of Trusses

The use of trusses brings up an important matter. Someone has to design them. Perhaps a few words about how the engineer operates might help. The engineer, in small house construction, is essentially a shortcut substitute for several years of costly trial-and-error on any new type of construction. His function is to predict the forces present in any system and the behavior of members under those forces. He accomplishes this through the use of standard engineering procedures. His value, to the builder, lies in his ability to design structural systems that will carry the imposed loads without waste of materials or labor--in other words, economical structures.

The trusses presented on the sheets which have been distributed to you are in two series. Each series consists of designs far spans from 16• to 32'. The first series has been designed far use where no attic storage is possible, while the second series has been designed~o carry an attic storage load, including any necessary flooring, of 20 p.s.f.

*Contributing personnel: J. T. Lendrum, I. T. Carrithers, P. Fung, F. Masek, c. McClain; J. Schwaiger and F. Creager.

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1. Slide: KING POST TRUSS Thi s is t he recommended truss for spans from 16' to 20'.

2. Slide: "W" '!RUSS This is the "W" truss which you will see constructed at full scale tomorrow afternoon. It is unique in several respects. Each of the three main rembers contains one lap splice. This all~s the use of ring connectors at the three major joints without the close tolerances that would ordinarily be required. It also allows the truss to be adjusted in span and to be laid up without splice plates, gussets or filler blocks. In addition, it may be subassembled and stored or transported in a minUmun space. The final assembly may be completed quickly OJ the job site. A full description and all the information needed to build this truss at any span from 20' to 32' is included in the material you have received.

Both series of trusses have also been designed for the dead loads (weight of the structure itself) and live loads (snow and wind) that appear on the stress diagrams included.

3. Slide: STRESS DIAGRAMS This is a stress diagram for the "W" truss; the design conditions are listed here.

4. Slide: STRESS DIAGRAM In areas where greater loads are possible,. the trusses must be redesigned. The loads, as _ given, are substantially correct for the State of Illinois.* The wind loads used are the result of the most recent research into the action of winds on houses. It is important to not, that, for this slope, the wind exerts a cor'siderable force tending to lift the roof from the building.

5. Slide: WIND DESTROYED STRUCTURE To the engineer, the value in tension of toe-nailing is so unpredictable as to make it valueless. For this reason, these trusses have been designed to be fastened to the wall plates wi t h light metal framing anchors which make toe-nailing unnecessary and load the nails in shear rather than tension. All of the trusses have been designed for a slope of 5 in 12 and are to be spaced 24" on center. Where t.he trusses are to be used for slopes other than 5 in 12 they must be redesigned.

*H.H.F.A. Performance Standards (1947)

18-

6. Slide: STRESS GRADE MARKINGS This is a stress grade marking. The wood must be of 1100 p.s.i. stress grade ~better:- This is equivalent to Coastal Region Douglas Fir #2 and is one of the lowest grades obtainable.

One of the most critical factors in the design of wood trusses is the design of the connections. Like a chain, a truss is only as strong as its weakest link. Too often ~ wood construction, it is the connection that proves to be the weakest link. It is useless to use a member size that will sustain the necessary load if the connection will fail at one-half of that load.

7. Slide: DETAIL NAILED JOINT (Lap or Splice) One of the main problems in truss design is the uncertain value of nailing, which in turn is reflected by a large factor of safety in the nail value. This causes the number of nails in the critical joints to become quite large. It is important that the proper number of nails be used. A badly split member mp · -~~ be replaced. It is this uncertainty about nailing that makes the use of ring connectors necessary where stresses are very high.

8. Slide: CUTAWAY RTl-i€1-CONNECTOR This is a ring connect~Q joint before assembly. Any variation in the location of the connectors will create a tendency for the joint to rotate and the resulting stresses have not been taken into account in these dr r: i. gns. Therefore,-we strongly advise that the connectcrs be located exactly as shown.

9. Slide: UNSATISFACTORY PIECE OF 1" MATERIAL You may have noticed that several of these trusses use l-inch members, and ~t the same time it is impossible to buy l-inch material that is stress graded. The Forest Products Laboratory at Madison, Wisconsin, has informed us that rules for the stress grading of 1-il"'ch boards will be published in their revised Wood Handbook. · In the meantime, the builder's judgment will be perfectly adequate for the choice of the pieces. Checks, shakes, and splits are unimportant--any piece without an excess of knots will be satisfactory. The slide illustrates an unsatisfactory 1-inch board.

10. Slide: 'WRONG OVERHANG Overhangs are very important both as a means of increasing sales appeal and as a practical means of minimizing the exposure of window frames to rain and snow. There are two ways of providing trusses with overhangs. The first way is to move the bearing walls inside of the heel joints. This method is illustrated in the slide. It causes extreme bending in the lower chord and must not be used unless the truss is redesigned.

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11. Slide: CORRECT OVER~JG The easiest method of providing an overhang is to extend the top chord. This method is illustrated in this slide. The stresses caused by this detail are not large and horizontal overhangs of' up to 30" may be obtained with a 2" x 4 '' top chord.

Briefly, the important things are these: Trusses a.re economical. They can be engineered more accurately than corresponding rafter and ceiling joist designs.

Uplift on the roof due to the wind is a major problem. Toe-nailing is undependable in tension and should not be relied upon. Light, inexpensive, metal framing anchors should be used to connect trusses to the wall plates. To derive the full benefits of engineering, the deeigns must be followed closely and used only for the design conditions. Overhangs of reasonable dimensions can best be achieved by extending the top chord.

Mr. Harrell will continue this discussion of trusses with more detailed remarks on economy and on assembly procedures.

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COST AND CONSTRUCTION PROBLEMS

Raymon H. Harrell Research Associate, Small Homes Council

My discussion will deal primarily with the "W" truss that Mr. Worth has mentioned to you. Recently in one of the laboratories on campus, we constructed two of these expandable trusses to see what problems or what qualities this designed truss has over other trusses that have been used during the past years. When the two pilot models were completed, we were very pleased with the results, for in this truss several problems have been eliminated.

As you see on the model, there are only five different lengths of material and all of that material is of one dimension; namely, two by fours. As far as lengths of material needed is concerned, standard lengths of 10' 1 12', and 14' will cut out for a lineal footage of waste approximately 4' long consisting of two pieces 12" long, two pieces 8" long, and two pieces 4" long.

In designing this truss, the amount of cutting was taken into consideration and held to a minimum in order to help reduce the over-all time required in the precutting qperation. Even with this minimum cutting it is not necessary to be exact for the lap joint in all of the main members will allow for any small deviations or variations that might occur in lengths.

As the most efficient means of ~carrying out such m operation, we have left two small angle cuts--one on each bottom ctord at the heel joint and one on each of the two long diagonals--as hatchet cuts to be made when the truss is removed from the jig or after it has been put in place prior to the sheathing operation.

This lap joint also takes care of the old problem of fastening continuous members at both ends with ring connector. With three rings in tris truss--one at each heel joint and one at the peak between the two top chords--the possibility of any racking is eliminated.

Following the instructions that you have been given, two carpenters should, within an hour, lay out this truss and cut a pattern model using either a skill saw or ~ radial arm saw. One carpenter and one laborer should then, within one working day, precut, bore, and preassemble the subassembly which you see on the mod.el for a rectangular-shaped house of approximately 1,000 square feet. On.e other thing that you have probably noticed is that within this truss there are no left or right members.

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This holds true even to the boring for the ring connectors. The only necessary or reasonable care that must be exercised during the subassembly concerns the peak joint. This assembly must be put together in all cases in one definite manner so that when preparing to nail the truss togeth~r the two top members, namely, the top chord and the long diagonal, can be moved to the left with the two corresponding members moved to the right. If this is followed, there is no difficulty in getting all of the members in their respective planes.

Since there must be some starting point in the assembly of the truss, we recommend in the printed matter that you start this procedure by laying out the lower right subassembly with the top chord resting on the subfloor. For the next step, the corresponding assembly is placed on the left with the top chord in a reversed position. With these two members in place it is then possible to put down the necessary blocking to fit the notches in the heel joints in order to give the over-all desired length. By using a steel square at the heel joint and the top chord, the desired pitch that you have decided upon is given to the truss. When this has been ascertained, chalk lines are snapped to the peak joint, thus giving you an over-all layout of the truss. The next step is to place the peak joint, swinging the top two members to the left, the bottom two to the right, and placing these members so that they rest within their particular plane. From this point on, it is a matter of nailing the proper members including the sbort diagonals in their respective places. Caution, however, should be exercised in that the nailed joints on the bottom chord should always be nailed from the top leaving a minimum of nailing to be finished once the truss is brought to the upright position. (Approximately four nails.)

Another feature of a truss of this nature is the minimum amount of storage space required for the subassemblies prior to the actual time of assembly and erectton. If this is done in a mill away from the construction site, it lessens trucking problems in that the longest member of any subassembly is 14 feet. This means that an ordinary 1t-ton truck is ample for any transportation problems that might arise and no special or large equipment will be needed. It is possible in areas where large volume is needed that subassemblies may be stocked in standard spans by contractors, builders, and maybe even some local lumber yards.

In the printed matter that you have, this truss is carried one step further and its main members used as outlining members for the gable ends with two minor changes. The lap joints ·become butt joints, and fillers are put in to bring all members on the top side into the same plane.

The finish material that is to be applied to the gable end will determine what type of vertical or horizontal supporting and nailing members are to be applied in place of the web members.

The economy that is achieved by using the truss is not by any means centered on the comparison between the truss and standard rafter and joist construction as such. There are other things to be considered, but in passing these are the dollar costs of materials. For the truss you

-22-

see here, the cost is $8.00 for a clear span of 25 feet. A rafter and joist of the same length and placed 2-feet on center, but with a loadbearing partition, have a material cost of $11.40.

Other economies that result from using the truss and add up to considerable savings in construction cost are:

1. Trusses can be erected very rapidly which puts the job under cover. This helps to eliminate delays due to weather conditions and makes complicated scaffolding or bracing unnecessary.

2. Side-wall and ceiling finish-material can be applied in one continuous operation. Sheet materials can be used with a minimum of waste.

3. The finish floor material can be put dmm over the entire house with a minimum of cutting and fitting. This results in savings in both labor and material.

4. Light non-load-bearing partitions can be constructed on the floor and tipped into place. This allows 100 per cent flexibility in the design and spacing of the house interior and eliminates extra supporting floor joist members.

5. Non-load-bearing closet partitions are also possible. This results in cost reduction in installation time and material, and at the same time provides a greater amount of storage space in the house.

6. Outside finish material can be applied to the gable trusses while they are still on the subfloor, thus saving many hours of labor. A study conducted by the Small Homes Council in 1950 revealed that t\relve manhours were saved in following this procedure as opposed to the method of two carpenters -vrorking from ladders and scaffolding -vmich was used on another house of identical size and design.

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THE KING POST 'mUSS

SPANS*: 16'-8" to 20'-8"

LOADING - The following king post truss has been designed to carry loads as listed in Figure 1.

SLOPE - 5 in 1~

SPACING - 24" on center

MATERIAL - Material must be 1100 p.s.i. stress grade or better. (Equivalent to Coastal Region Douglas Fir #2)

ASSEMBLY PROCEDURE

1. Compute out-to-out dimension of exterior wall plates. 2. Locate this dimension in Table I and read down--the individual

member sizes and the total lumber for one truss may be taken from this table. Where your span falls on the dividing line between member sizes, use the member size to the left.

3. Cut members for one tru~s according to cutting diagrams in Figure 2. The lengths of the members have been omitted from these diagrams. It is felt that the assembly is similar enough to rafter construction so that the calculation of these lengths for a particular span is no problem to the builder.

4. Lay out necessary chalk lines and out-to-out dimensions of plates to align bottom chord notches. NOTE: If building truss with no attic load, consult heel joint detail in Figure 4.

5. Assemble truss as illustrated in the three steps of Figure 3. 6. Check the accuracy of all cuts. 7. Disassemble; using members as a pattern. cut remainder of trusses. 8. Assemble; nail each member as it i~ laid according to details and

nailing schedule shown in Figure 4. 9. In nailing trusses to exterior wall plates, use metal framing

anchors.

Overhangs - Overhangs should be achieved by extending the top chord. The :mwc:i.mum. allowable overhang for the 2" x 6" top chord is 44", measured horizontally.

Intersections - Modify truss as shown in Figures 19 and 20.

*NOTE: In the following discussions, tables and drawings, the term 11 spa.n" refers to the out-to-out dimension of the exterior wall plates.

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COPYRIGHTED 1952 BY THE UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL. ALL RIGHTS RF.SERVED. Responsibility for houses built from these dra\lings shall rest with · the user of the drawings and in nowise on the University of Illinois. When variations from the original c:travings are incorporated by the user, the structures built shall not be represented as being built from a design developed through research at 'the University of Illinois.

Endorsement by the University of Illinois for any mnufactured product shall not be claimed on the basis of these drawings or related information thereon.

!op Cbord top Chord

Vertical

Lap loint Bottom Chord

IIRG 1WT TR¥§

LOADING

Ser1• l SPACDG - 24" on center Seriea B

lo Attic Storage Boot!Dg- 2. 5 pat

Attic Storage- 20.0 pet (1Dcludee neceeaa.J7 flooring)

Sheath!Ds- 2.5 pet Root!Dg- 2. 5 pet Traaa- 2. 5 pat Sheathing- 2. 5 Plf Snov- 20.0 pet !rasa- 2. 5 pet Wind- 23.0 pst (up].ift) Snow- 20.0 pet

V1D4- ~.o pet (uplitt)

Figure 1 UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL

COPIRIGRTED 1952 BY THE UNIVERSITY OF ILLINOIS SHALL HOMES COUNCIL, ALL RIGHTS RF.SERVED. Responsibility for houses built from these drallings shall rest with the user of the drawings and in nowise on the University of Illinois . When variations from the original C1rawings are i noorpor ated by the user, the struotures built shall not be represented as being built from a design develor-ed through research at t.he University of Illinois ,

Endorsement by t he University of Illinois for any manufactured product shall not be claimed on the besis of these dra11ings or related information thereon,

I I I I I I I I I I I I f-J f-J f-J f-J ...... ...... f-J ...... ...... ...... l\) l\) l\)

SPAN t b ~ & b f t b 'f. t b l ~ (out-to-out) i. of.'

TOP 2- 2 ~ X 6" - 14'• ~-2 X 6" - 161J CHORD*

~~~ BOTTOM

CHORD 2- 2' X 4" - 10 1 ~ 2- 21 X 4" - 12'• ~e iH VERTICAL 1- l"x4"' ~· 1 "!

'"" X 4' - 5' - ..

TOP n X 6' ~- 2' X 6n - 1611 CHOBD* 2 - : -14 s

BOTTOM en

2- 2' X 6" 2 -: n X 61 -12 ~~~ CHORD - 10 1 ~ s

~s -VERTICAL 1. 1 11 X 4• - ~ ~·

*Member lengths shown here are eutficlent for a 30" horizontal overhang. Revise it another overhang is desired.

MEMBER SIZF.S - KING R8T TRUSS

Table I UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL

COPIRIGHTED 1952 BY THE UNIVERSITY OF ILLINOIS SHALL HOMES COUNCIL. ALL RIGHTS RF.SERVED. Responsibility for houses built from these drawings shall rest with the user of the drawings ar,d in nowise on the University of Illinois. When variations from the original C1ra11ings are incorporated by the user, the structures built shall not be represented as being built from a design developed through research at t.he University of Illinois.

Endorsement by the University of Illinois for any mnufactured product shall not be claimed on the basis of these drs11ings or related information thereon.

C)/" s ,,

~ ,-+--- 2" X 6"

~~3%1 TOP CHOBD --Trim. with hatchet

when sheathing :i J _[' __________ 2_" __ x __ 6_• __ o_r __ 2_"_x __ 4_"----~~ 1~--------------------------~~

BOTTOM Q!!Q!Y!.

111 square cute

1n X 4n

VERTICAL

CUTTING DUGR&M9 - ~ ~ TRUSS


COP!Rilifl'l'EI) 1952 BY THE UNIVERSITY OF IU.IHOIS SMlLL HOMES COUNCIL. ALL RIGHTS RF.SERVED. Responsibility for houses built from these drallinga shall rest with the user of the drawings and in nowise on the University of Illinoill. When variatiou from the origiDal C1rawings are incorporated b:y the user, the structures built shsll not fle represented as being built from a design develoJied through research at t.he University or Illinois.

Step 1

Step 2

Stel?3

3

EDdorsement b:r the University or IlU.nois tor any manufactured product shall not be claimed on the basis or these drawings or related information thereon.

OBDBR 07 ASSEMBLY ... KDG POST 1'RtSS

Notes Far member eisea, eee Table I; tor nalla, see Figure 4.

UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL

COP!RIGHTED 1952 BY THE UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL. ALL RIGHTS RF.sERVED. Responsibility for houses built from these drawings shall rest with the user of the drawiage and in nowise on the University of Illinois. When variations from the original drawings ere inoorpore.ted by the user, the structures built shell not be rept"esented as being built from a design developed through research e.t "the University of Illinois.

Endorsement by the University of Illinois for aey manufactured product ahe.l} not be claimed on the basis of these drawings or related information thereon.

SPAR

1618" & less 1619" - 1718" 17'9" - 1818" 18'9" - 19'8" 19'9" - 20'8"

!Ml Jo1Dt B8t"Veen Top

1, &: Bottom f Chords

RO ATTIC STORAGE

8-lOd 9-10cl 9-10d

1o-10cl ll-lOd

Attic Storage

ATTIC Peak Joint Between -Top Chorda

STORAGE

~lOd 15-lOd 15-lOd 16-10d 17-10d

SPAR

16'8" & less 1619" - 1718" 17'9" - 1818" 1819" - 1918" 191911 - 20'8"

Splice Between Bottcm Chords

10 ATTIC ATTIC STORAGE STORA.GI

8-lOd 13-10d 8-lOd 14-lOcl 9-10d 14-lOd 9-lOd 15-lOd

lo-lOd 16-10d

RAILDG SCBEDULI - KIRG P<ET TRUSS

Vertical to Peak ! Bottom Chord

' NO ATTIC ATI'IC SPAll STORAGE STORAGE

16'8" & less 4-8<1 5-Sd 1619" - 1718" 4-Sd 5-Sd 17'9" - 1818" 4-Sd 5-Sd 1819" - 1918" 4-Sd 5-Sd 19'9" - 20'8" 4-Sd 6-8d


THE "W" muss

SPANS*: 20' -8" through 32' -8"

The "W" truss that is presented on the following sheets has been designed to offer many advantages:

1. It may be used economically at any span from 20' -8" to 32' -8" out to out of plates.

2. It allows the use of ring connectors at the highly stressed joints without the need for working to close tolerances that this would ordinarily require. (The sliding laps in all the main members make this possible.)

3. It eliminates the need for splice plates, gussets or filler blocks. 4. It allows the trusses to be subassembled (by semi-skilled labor)

without concern about "lefts" and "rights" and with simple visual checks as to the correctness of the assembly.

5. While subassembled, the trusses may be stored in a minimum space until needed.

6. It is possible, in this manner, to complete the subassemblies off the site in advance and to truck them in, When required, without the use of large or special equipment. (A pickup truck is sufficient.)

7. It will be possible for lumber yards and mills to quickly cut and subassemble these trusses for any span upon order from contractors and builders.

8. The final assembly of the parts may be made quickly upon the subfloor of the building, without regards to "lefts" and "rights':

9. In areas where the building volume makes it possible, the subassembled trusses may be stocked in standard spans by contractors, builders or lumber yards.

10. The truss may be assembled as two identical halves. Final assembly would then consist of inserting one ring and bolt and nailing one splice.

The "W" truss has been engineered for the following design conditions:

LOADING - As listed on stress diagrams, Figures 5, 6, 7 and 8. There are two series of trusses. The first series has been d~signed for use where no attic storage is possible. The second series has been designed to carry an attic storage load of 20 p.s.f.

SLOPE - 5 in 12

SPACING - 24" on center

MATERIAL - Material must be 1100 p. s. i. stress grade or better. (Equivalent to Coastal Region Douglas Fir #2)

*NOTE: In the following discussions, tables and drawings, the term "span" refers to the out-to-out dimension of the exterior wall plates.

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COPIRIGBTED 1952 BY THE UNIVERSITY OF ILLINOIS SW.LL HOMES COUNCIL. ALL RIGHTS RF.SERVED. Reeponaibillt;r for houses built from these dra!linge shall rest with the user of the drawinge and in nollise on the Universit;r of Illinois. When variations from the original drawings are incorporated b;r the user, the structures built shell not be repr'esented as being built !':rom a design develo~ through research at t;he Universit;r of Illinois.

Endorsement b;r the Universit;r of Illinois for an;r manufactured product shall not be claimed on the basis of these drawings or related information thereon,

L, · . 3~3l. L I ·

SLOPE - 5 in 12 SPACDQ - 24" on center

Figure 5

t 13.75

Lz - . 33.3L

L

IZ.

~5

LOADING

Upper~ Snow Load Boo~ing Sheathing Truss

Lover Chord CeUing No Attic Storage

20.0 pst 2.5 psf' 2.5 pst 2. 5 psf'

3.0 psf'

A

13.75L

I ..J

~

r----------(_T~)----------~~------------------~G ~

54. 4t;, L - L, ( T)

STRESS DIAGRAM "lP TRUSS

NO ATTIC STORAGE

Zl


COP!RIGHT!D 1952 BY THE UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL. ALL RIGHTS RF.SERVED. Responllibility for houses. built from these dra\I!Dgll shall rest with the user of the drawing!! and in no>Tise on the University of Illinois. When variatio!lll from the original drawings are incorporated by the user, the stru.ctures built shall not be represented as being built from a design developed through research at t.he University of Illinois.

D

7.7SL

c

SLOPE SPACING

Figure 6

Endorsement by the University of Illinois for any manufactured product shall not be claimed on the basis of these drawings or related information thereon.

5inl2 24" on center

12..52. L- Qt.

12..5ZL-Il,

\'l-• A-1"'

' !)A-'Z,\.-

3.7SL ~

~ 1\\,

.'t-

L,- .333L

.1-

(p. 'l-~\.-, I c.~3J.

+ ZL

Lt.- .33~L

L

LOADING P.P.2!!: ~

Wind 2.3. 0 pst Roofing 2. 5 pst Sheathing 2.5 pat Truss 2. 5 pat

STRESS DIAGRAM "W" TRUSS

!Q ATTIC'STORA.GE

~ ZL

1'~ .• }'1..

·S~ <i..

~ 3.75L

£...

Lover Chord Ceiling .3.0 pat No Attio Storage


COPIRIGHTED 1952 BY THE UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL. ALL RIGHTS RF.SERVED. Responllibility for houses built f'rom these drawings shall rest with the user of the drawings and in nollise on the University of Illinois. When variations f'rom the original c1ravings are incorporated by the user, the structures built shall not be represented as being built f'rom a design develor.ed through research at t.he University of Illinois.

Endorsement by the University of Illinois for any manufactured produot shall not ~ claimed on the basis of these drawings or related information thereon.

~ 1,.33L

l..

SLOPE - 5 in 12 SPlCI!G 24• on center

LOADIRG

Upper Chord SDov Load Boot1Dg Sheathing !russ

Lover Chord Ciillii

20.0 pat 2.5 pst 2.S pet 2.5 p&t

3.0 pst

+ I

Light Storage 20.0 pet Includes Recessar,y

PlooriDg

58 L · La. (T)

8{;. 85 l.. - l.' (l

S!RISS DIAGRAM- ·T BUSS lftiC S'lOil.lGB

A

~.875L

13.75L

15.33L

1


COPIRIGHTED 1952 BY THE UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL. ALL RIGHTS RFSERVED. Responllibillty for houses built from these drawings shall rest with the user of the drawings and in nowise on the University of Illinois. When variatio%1.11 from the original drawings are incorporated by the user, the structures built shall not be represented as being built from a design develot:ed through research at 'the University of Illinois.

z

Figure 8

Endorsement by the University of Illinois for any manufactured produot shall not be claimed on the bads of these drawings or related information thereon.

L~ · I0.8L - (T) r-----~~------------~H

7-7SL

l 1.875L

~--~--~~~----~----~--~~~--~~----------------~ ~ I L • . 333 L. I Lt - • 333 L I t 7.t:.7 ~ t 15.'33L f 7. f.7 L

LOADING

Upper~ WiDd

Roofing

I

23.0 psf (uplitt)

L

SLOPE

SPACING

~

51n12 24" on center

A Sheathing 2.5 psf' 2.5 psf' 2.5 psf' Truss

4. 54L Lower ~

(.T) I

Ceiling 3 .o psf' Light Stor. 20.0 psf'

Includes Necessary Flooring STRESS DIAGRAM

11W11 TRUSS ATTIC STORAGE


COPIRIGHTED 1952 BY THE UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL. ALL RIGHTS RF.SERVED. Responsibility for houses built !rom these drawings shall rest with the user of the drawings and in novise on the University of Illinois. When variations !rom the original drawings are inoorporated by the user, the structures built shall not be res:resented as being built !rom a design develo~d through research at "the University of Illinois.

Endorsement by the University of Illinoia for aey llllllllUf'actured produot shall not be claimed on the basis of these drawings or related information thereon.

Lower Top Chord

Bottom Chord

Bottoa Chord

{

Lower Top Chord

Figure 9

Short Diagonal

t

Long Diagonal

2i" Split Rin1 t" Bolt

Long Diagonal \

{

Short DiagoDAl

Lover Top Chord

f

Bottom Chord

Use framing anchor as shown to clear bolt. The same type ot anchor is used on both left and right plates and in each case is nailed to the bottom chord. In spacing the trusses, the measured distance to the triangular flange or the anchor is the same for both lett and right plates.


ASSEMBLY PROCEDURE - "W" t ss, any span~

1. 2.

3.

4.

9.

10.

11. 12.

13.

14.

15o

16.

2lo 22.

Compute the out-to-out dimensions of the exterior wall plateso Locate thi dimen ion in Table II and read down--the individual mem er izes and the total lumber for one truss may be taken from this table o Where your span falls on the dividing line between member izes, u e the member size to the lefto Note the size of bottom and top chords for your span., Cut members for one truss as shown in the cutting diagram for your com ina ion of top and bottom chords. (Figures 10 and 11.) Work f om one end of the piece only--the member lengths given have been calculated to provide sufficient lap for the nails requiredo

omplete the 3 subassemblies as shown in Figure 13. Bring bolts up finger ight. If cut and drilled correctly, they cannot be assembled wrongo (There are no "lefts" and "rightst'--the two heel joint are identical.) Lay out hori ontal balk line as shown in Figure 14, with perpendi ular line at its approximate center. Nail blocks #1, evenly spaced from vertical center line, so that out-to-out dimension of blocks corresponds with out-to-out dimension of exterior wall plates. Lay out 1/6 of span and 1/4 of span on either side of center line; at 1/4 points mark lines parallel to center line. Place a heel assembly on subfloor so that notch is in position to fit right block and top chord is on subfloor, bottom chord on top chordo Push assembly into place until notch fits block tightly and bottom chord is in line with chalk line. Rotate upper hord until steel square shows a slope of 5/l2o (See Figure l5o ) Tack with one nail to hold slope. Run chalk line along top chord edge until it intersects center line. Nail block #4 near peak along chalk line and block #3 near heel. (See Figure 16o ) Repeat for left heel assembly (lay down so bottom chords lap- -left over· righ .) Pull nails holding slope and, with block #2 at center line, put in 1/2" camber allowing bottom chords to rotate and holding top chords again t blocks #J. Take peak assembly and open so that two bottom members go right, two top members go left. Place chords (2 central members) tightly against blocks #3 and #4; slide left-hand hord under left member already placed, right-hand chord over right member already placed. Check alignment of all memberso Swing left diagonal down until at 1/6 point marked previously. Mark the neces ary cut on left diagonal. Put right hort diagonal into place so that it intersects bottom chord at 1/6 point and top chord at 1/4 point. Mark necessary cut on short diagonal. Recheck alignment of all members and make sure notche~ are against

lock o

-36-

23 o Disassemble truss and cut diagonals slightly short of mark o 24 . Use completed mem ers as a pattern and cut remainder of trusses. · 25. Bolt s bassembl ies together and stack. 26 o Lay up each truss in steps similar to original, using original

blocks as a jigo 27. Nail each member a s placed according to nailing schedule presented

in Figure 12 .

In the following des igns, t hese points should be noted:

1. The length of the bottom half of the top chord has been computed and the cutting diagrams for that member have been drawn for a 30-inch horizontal overhang. This is the maximum allowable overhang for a 2" x 4" top chord o However, for a 2" x 6" top chord, a horizontal overhang as large as 44 inches is possible. If an overhang other than 30 inches is preferred, the cutting diagrams and lower top chord member lengths must be changedo

2 o This truss may be used for any span from 20 '-8" to 32 '-8" if the cutting diagra~s and member sizes are followed. However, there are some spans at which there will be a minimum of unnecessary lap when the individual members are cut from standard lumber lengths. For an individual member size and length, the span corresponding' to the righthand edge of the appropriate box in Table II is the span at which there i s no unnecessary lap for that member o If a free choice of span is possible, car eful study of Table II will indicate the span that will give the minimum amount of wasted lap.

3. Certain of the long diagonals in Table II are marked with an asterisk. These must be braced late1ally at their center point either by running a 1" member between trusses and edge nailing it to the diagonal or by using 2" solid blocking between trusses.

4. A "camber" of 1/2 i nch is shown at the center of the bottom chord for all spans. Thi s i s an estimate as to the amount this point will drop as t he truss adjusts i tself under load. Putting this camber in will help preserve a smooth horizontal ceiling in the finished structure.

5. The height to which the guide blocks are built up has been left to the discretion of the buildero It is advised, however, that those blocks which fit the top chord notches be built up sufficiently to keep the notches in contact during all phases of the assembly.

6. There is no need for filler blocks or for the warping of any of the truss members.

7. Sufficient time should be spent on the pattern truss to familiarize the workmen with the assembly procedureo The remaining cutting and assembling will go rapidly and without fear of error.

8. The trusses have been designed to withstand uplift. In nailing trusses to ext erior wall plates, use metal framing anchorso (See detail, Figure 9 o)

~37-

COP!IUGBftD 1952 B! TH! UIUVERSIT! OF ILLIIOIS SMlLL HOMES COUJ«:IL. ALL RIGHTS RF.sERVED. Responaibillt:r ror houaea built Croll thue drallf:agll ahall rest with tbe user or the drawinge and in nowise on the Uninrllit;r or Illinois. When variatioDII b-oa the origiDal arawinga are incorporated b)- the user, the structure• built shall not be repr-esented as being built troa a design developed through reaearch at t.he Univerllit:r or Illlnoia.

'!Ddora-nt b)- the University or Illlnoia ror •111' •nutactured product ahall ncit be clailled on the bailie or theae drawings or related inforaation thereon.

I I I I I I I I I l I I l ~~ ~ ~ N l\) N l\) N N \1.) \1.)

b b b b b b b b N &; SPAI' b b (out-to-out)

2 1JPPEil TOP :'" . ~"' It 4 ,.• l - 21 ~ J ~ It ~ : ~6· ~ . ~~~ ~~ >" X ~s· ~ ~ : It ~ 6tt 2" X ~"

CHOBD ]~I : Qls l2'•

LOWER TOP :~

l 6~ ~ - 2~ : ~ i • 1- ~0 s 2~ : ~ ~ n 2 1- ~· X 6• -].; ~·e 2- 2' CHORD* 1.: ~·~ 1.4 .... BOTTCM

2" X 41 ~ . "' ~ • ~ ~· ~ •• :~ . ~· ~ ~It X 16 'a ~ - 2 ~ : .. ~" 2 - -CHORD P-2 •a ·,..s s

SHOll! DUGODL 1 -11 l J..

"' ~ IJ' ..,

- 2 "' ~· •" X a• 1 -2" X 41 l l P' ..

LORG ..,

DUGORAL ] - 1f ~ ~ ~ It ~ ~I •• ~ ~ 1- 2 l " " ~ : .. 6• ·~ 1 - ~It X 4" 2 1 ~· ••

Jj

*TM length ot thMe Maben baa bee comp1ted to provide a 30" horizontal overhang. It a ditterent overhang is deairecl, rerlae these lengths and the cutting diagrams.

**X.terall1' brace long diagonal at center. •!" TRES MEMBER SIZES

(Contilma4 on the neD sheet)

z 0 ,. ~ ~ -0

en ~ 0 :u )> G) 1"1

Table II UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL

COPIRIGBT!D 1952 BY THE UlfiYmSIT! OF ILLINOIS SMALL HOMES COUNCIL. ALL RIGHTS RF.sERVED. Reapon.llibilit;r tor houses built from these draw:f:DgS shall rest 11ith the user of the dra11iDgS and in nollise on the Universit;r of Illinois. When variationa from the original C1ralliugs are incorporated by the user, the structures built shell not be represented as being built from a design develoted through research at "the University of Illinois .

Endorsement by the University of Illinois for an;r mnuf'actured product shall not be claimed on the basis of these drawings or related intormation thereon.

- l I l l l l I I I l I l I l l\)l\) l\) l\) l\) VJ VJ

~b l\) ~ t "' b b b b b

,_, ~

l\)

SPAB b b b b I <»

(out-to-out)

UPPER -

TOP 1 - 2 I ::l ~" :'" . 2 " X: ~" X ~6~ "' - 2 ' : ~" Pc .. 8 ~ . ~ ~ n ~ f>u - 1C 's ...

CHORD . lj ~·

LOWER )>

TOP 1 - 2 . J ~n 2 - 21 I ::l E" ~ : 2 1s :~ - 2" ~~ ~" -i CHORD* 18• l ~·~ -i -

0

BOTTOM 2 2 I

(/) CHORD ~· IX ~" 2' X ~" ~ - 2~ : ~ 6" i-14 s 2 - ~" X 6fl -lp'•' ~ . .. ~ 11 pc p" -i ~2 ~ 12 t J s·~ 0

::a SHORT I J>

DIAGONAL 1- l~ JC 4~ : ~ ~ ' 1 -2" X 41 J s• J - 2, ~ ~ ~ n I'C ~0 Ci)

1"11

LONG . .

DIAGONAL 1- 1" X 6 ' ~ l4' 2~ ~ ,. ~" l - 2" X 41 :X 1 ~· :'" . ~ ~ " ~ n X lSI + 1~'

*The length of these members baa been computed to provide a 30" horizontal overhang. It a different overhang is desired, revise these lengths and the cutting diagrams.

"W" TRUSS MEMBER SIZES -- -Table II, Continued UNIVERSITY OF ILLINOIS SMAll HOMES COUNCIL

COPIRIGBT!D 1952 BY THE UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL. ALL RIGHTS RF.SERVED. Resf:Onalbillt:y tor houses built trom these drawiags shall rest 11ith the user or the dra11ings and in nollise on the Universit:y or Illinois. When variations from the original C1rav1ngs are inoorf:Orated b:y the user, the structures built shall not be represented as being built trom a design develo~d through research at ~he Universit:y of Illinois.

Endorsement b:y the Universit:y or Illinois tor an:y JMnufactured product shall not be claimed on the bash of these dravings or related information thereon.

BOTTOM CHORD - Drill for 2 1/2" - Ring as Shown

ClJ'rriRG DIAGRAMS - "W" fttsS m;! SLOPE -

2"x 4" Use With 2"x 4" Top Chord

~" Use With

' 2 11 X 6" Top Chord

2"x 6" Use'iith 2"x 4" Top Chord

2"x 6• Use With 2"x 6" Top Chord

J'igure 10

·~~--\~

em-------+--i --~ LORG DIAGONAL - Drill for 1/2"

- ',~,lt as ~Shown l"x 4" or 2"x41 - ~ Use With _ 211 X 4" Top Chord

~-- j ·-~, ~-------+----,

~~ -- ..

I :3.

~~'% .. "'\tO

------------------~----~

,~-- -~ 1" X 6"

I I " 4~

I All bevels :ma.y be le:rt as hatchet cuts. ROTE:

CONTINUED 01 FIGURE ll - -UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL

COPlRIGHTED 1952 BY THE UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL. ALL RIGHTS RF.SERVED. Responsibility for houses built f'rom these drawings shall rest with the user of the drawings end in nowise on the University of Illinois . When variations from the original Cl.rewings are incorporated by the user, the structures built shall not be repr-esented as being built f'rom a design develot-ed through research at t.he University of Illinois .

Endorsement by the University of Illinois for any manufactured product shall not be claimed on the basis of these drawings or related information ther eon.

CUTTING DIAGRAMS - "!" 1'RtJSS 5/12 SLOP.B

IDlER TOP CHOBp Drill For 2 l/2" Ring aa Sbovn

....----+-----+-~·~· UPPIR !OP CHORD

2":x: 4" Use With 2•x 4" Bottom Chord

~" · U&eVith 2"x 6" Bottom Chord

2•x 6• ifSe With 2•x 4" Bottan Chord

2"x §" UeeW1th 21tz 6" BottaD Chord

2"x 4"

2"x 6"

I " z. '. <J ~

r---+---+----=\r SHORT DIAGONAL

l"x 4"

~:

Drill For 2 1/2" Ring as Shovn

<

s:."' 3~

Mark Cut Duri.nl Pattern Asaemb]3


COPIRIGRTED 1952 BY THE UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL. ALL RIGHTS RFSERVED. ReSf01111ibility for houses built from these drawing& shall rest with the user of the drawings and in nowise on the University of Illinois. When variation& from the original drawings are incorfOrated by the user, the structures built shall not be represented as being built from a design develor,ed through research at ~he University of Illinois.

Endorsement by the Universlty of Illinois for an;y manufactured product shall not be claimed on the beds of these drawings or related information thereon.

TOP CHOBD SPLICE

No Attio Attic

20 18" & less 15-lOd 24-lOd 20 19" - 22•8• 17-lOd 26-10d 22 19" - 2418" 18-lOd 29-lOd 2419" - 26 18" 2Q-10d 31-lOd 2619" - 28'8" 21-lOd 33-10d 28 19" - 30 18" 22-lOd 36-lOd 30'9" - 32 18" 24-lOd 38-lOd

SHORT DIAGONAL TO TOP & BOTTOM CHORD

20 18" & less 20 19" - 22'8" 22 19" - 24'8" 2419" - 26'8" 26 19" - 28'8" 28 19" - 30*8" 30 19" - .32 t8n

Figure 12

No Attic

4-Sd 4-Sd 4-Sd 5-lOd 5-lOd 5-lOd 6-lOd

Attic

4-Sd 4-Sd 4-lOd 4-lOd 5-10d 5-10d 5-lOd

20'8" & less 20 19" - 22'8" 22'9" - 2418" 24'9" - 26 18" 26'9" - 28'8" 28'9" - 30 18" 30'9" - 32'8"

4-8d 4-8d 5-&l 5-10d 5-lOd 5-lOd 6-lOd

NAILING SCHEDULE

"!" TRUSS

8-8d 9-8d

10-10d ll-lOd 12-lOd 13-lOd 14-lOd

SPLIT RINGS SPANS: 20•::Sn to ~2 1-8"

WITH OR WITHOUT ATTIC STORAGE

1- Ring plus PEAl Bolt between

Top Chords

HEEL 1 - 2f" Ring plus i" Bolt per joint

BOTTOM CHORD SPLICE

s 20 '8" & less 20'9" - 22 18" 22'9" - 24'8" 2419" - 2618" 26 19" - 28 18" 28 19" - .30'8" 30 19" - .32 18"

No Attic Stora

10-10d 10-lOd 11-lOd 12-lOd l3-10d 14-lOd 15-lOd

Attie

15'-lOd 16-lOd 18-lOd 19-lOd 21-lOd 22-lOcl 24-lOd


COPIRIGHTED 1952 BY THE UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL. ALL RIGHTS RF.SERVED. Responsibility for houses built from these drawings shall rest with the user of the drawings and in nowise on the University of Illinois . When variations from the original drawings are incorporated by the use>", the structures built shall not be represented as being built from a design develop~d through research at t.he University of Illinois .


Lover Top Chord

Lett and right heel assemblies are the same. Out, drlll and bolt members identical 17.

~~------~L-·------------~ Bevel on bottCIIl chord mar be left tor a hatchet cut. It precut, when the aesembly is folded, the bevel should appear opposite trom the notch in the top chord.

£!W l5mii SUBASS~LY

Upper Top Chord

l-2f" Split Ring Between Chords

When assembly is opened, two bottom members go to right and two top members go to lett.

U opened assembl;r does not appear as above, ring grooves have been drUlecl on wrong side,

When folded, assembq looks like this fran either side - top chord bevels opposite - right bevel 1D front or left. Bevel Oil long diagonal mq be left tor a hatchet cut. !! precut, bevel !§. gn !!!!!!. !J!! !!. !!!!!! 2! top chord !! adjoins.

+

UNIVERSITY OF ILLINOIS SMALL HOMES ~OUNCIL

COPIRIGHTED 1952 BY 'filE UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL. ALL RIGHTS RRSERVED . ResJX>nsibllity for houses built from these drawings shall rest with the user of the drawings and in nowise on the University of Illinois . When variatioll.ll from the original drawings are incorJX>rated by the user, the structures built shall not be represented as being built from a design developed through research at t.he University of Illinois .


LAY OUT 011 SUBF.LOOil ---1 IVertioal 1center I LiM

I --+-

1

:; :

-~--t--I

BASIC CIIW{ l=.m LlYOtrr

"!" TRUSS

1/2 Spen

NOTE: The term •span• retere to the OU'b-to-out dimensions ot the exterior vall plates.

Pigure 14 UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL

COPJRMRT!D 1952 BI THE UMIVE7tSITI or ILLINOIS SMlLL HOMES CO~IL. ALL RIGHTS RF.SERVED. Reeponaibillt;y tor houses built from these drallinga shall rest with the uaer or the drewinga and in novise on the Uninrsit;y or Illinois. When variations from the original c:trav1ngs are incorporated by the user, the structures built shall not be reJresented as being built from a design developed through resear ch at ~he University of Illinoill .

Endorsement b;y the University of Illinois for any 11111nutactured produot shall not be clsillled on the besis of these drawings or related information ther eon.

t "~ook4 I ~~ I ChalkLine

I Block 3

I I Vertical I Center Line

I

i CWUkL-in-e--------------~~~~------------------------~ 1/2 Span

Right bottom chord goes under lfl1 bottom chord

SLOPE LAYOUT

NOTE: The height to vhich the guide blocks are built liP has been lett to the discretion ot the builder. See discussion in text.


COPYRIGHTED 1952 BY THE UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL. ALL RIGHTS RF.SERVED. Rea):Ondbillt;r for houses built from these drawings shall rest with the user of the drawings and in nollise on the Universit;r of Illinois. When variationa from the original drawings are incor):Orated b;r the user, the structures built shall not be represented as being built from a design developed through research at ~he University of Illinoill.

Figure 16

Endorsement by the Univereity of Illinois for any manufactured product shall not be claimed on the basis of these drawings or related information thereon.

NOTE&

!stD~paJa I I

PLACEMENT OF GUIDE BLOCKS YTRms -

1/2" caber measured above horizoDtal chalk line at centerline.


Gable-End Walls for "W" Trusses

Experience has shown that gable-end walls which are framed and finished on the subfloor are more economical than identical walls built in place .

Figures 17 and 18 present a method of accomplishing this, using the truss jig as a guide for the framing. The gable rafters are identical with the truss top chords and may be cut from the same diagrams. The drawings shown are for a finish material of horizontal siding applied without sheathing. The system may be adapted to any other type of finish material and framing for louvres may be cut in where desired. It is suggested that after the gable-ends are framed, they be taken out and stacked until the wall framing has been assembled and tipped into place. The gable-ends may then be returned to the subfloor and the finish material applied. They are then ready to be lifted into place.

-47-

COPIRIGIIT!D 1952 BY THE UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL. ALL RIGHTS RF.sERVED. Reeponaibillt:y for houses built from these drawings shell rest with the user of the drawings and in nowise on the Universit;r of Illinois. When variatioDa from the original <1raw1ngs are incorporated b:y the user, the structures built shall not be represented as being built from a design develot-ed through research at "the Universit:y of Illinois.

Figure 17

Endorsement by the University of Illinois for any mnufactured product shall not be claimed on the basis of these drawings or related inforuation thereon.

ASSEMBLY PROCEDURE

12

Fill er Bl~ 5

Step 2

Step .3 - 2" :x: 6" on edge

!YPICAL GABLE-END WALL (Horizontal Siding}


COPlRIGHTED 1952 BY THE UNIVERSITY OF ILLINOIS SHALL HOMES COUNCIL. ALL RIGHTS RF:SERVED. Responsibility for houses built from these dra\ling8 shall rest with the user of the drawings and in novise on the University of Illinois. When variatiolll!l from the original drawings are incorporated by the user, the structures built shall not be represented as being built from a design developed through research at t.he University of Illinois .

Figure 18

Endor sement by the University of Illinois for any manufactured product shall not be claimed on the ba!i8 of these drawings or related information thereon.

ASSm.IBLY PROCEDURE (Continued trom Figure 17)

Step 5 - Filler Blocks Step 6 - Nail on Siding

SCHDflTIC SECTIOR

Upper Section Top Chord-~

Splice 211 x 6" Provides NaUiDg Area for Ceiling Finish

Finish Stud

Filler

Lower Section Top Chord

Horizontal Siding to Lap Lower Finish

Finish Sheathing

TYPICAL GABLE-END WALL (Horizontal siding)

Step 7 - Nail Framing Anchors Between Top Chord

and 2" x -6"


THE INTERSECTION OF TRUSSES

Intersection of 16•-8" King Post Trusses and 24'-8" "W" Trusses

Figures 19 and 20 give all the information necessary to modify regular 16•-8" and 24'-8" trusses which are at intersections. These modifications are necessary to the through-span trusses in order to carry the concentrated loads caused by the framing of the intersecting span. The trusses involved in the intersection of the spans have been numbered in the drawings at the top of each table. Only those trusses that are specifically mentioned in the table need be modified, but it should be noted that there are two trusses for each number--one on each side of the center line of the intersecting span.

The trusses of the through span must be supported at the intersection by a beam or bearing wall. In addition, the through span should be sheathed past the point of intersection on each truss and jack rafters or small trussed frames may then be erected on top of the sheathing to complete the framing of the intersecting span. Complete sheathing of the through span is not recommended since adequate ventilation between the attic spaces of the two spans is necessary.

-50-

I \A ..

j ....

"

COPIRIGRTED 1952 BY THE UNIVERSITY OF ILLINOIS S~IALL HOMES COUNCIL. ALL RIGHTS RF'SERVED. Respolll!libility for houses built f'rom these drawings shall rest with the user of the drawings and in novis e on the University of Illinois . When variations f'rom the origin&l drawings are incorporated by the user, the structures built shall not be represented as being built f'rom e. design develo,_ed through research at t.he University of Illinois .

Endorsement by the University or Illinois for any manufactured product shall not be claimed on the basis of these drawings or rel ated information ther eon.

l~c!1ioJ¥1 I Modif'ioatioM

! i

~ 0 ~ g Ct-

i : ~ i t-t

i

~ -i , .... ~ ........ ~ ~ I ~ ~

2 & 2 ! a s ~

~ I ~ ~ .... ~ ~ b 2 ! 2 i

to Pattern

and

Member

Sizes

='

I I 1\)

==

I I \,.)

~ I ~ ~ ~ ~ ~ _ 'f'~·~t .... ~ . 0 i g,

I

~ Iii 1~ r ~ ~ ~ I I! l! ~ ~ -....J...._~f-------"1 + I ~

~ ! c+

~o~if~~~ ~f--------'1 ~ S I If If ~ ~ s

..£_--+------, ~ ~

I

f ~ I 1\)~ 1i ~~~ 2

MDclitica:t~

to Pattern

aDd

Meaber

Sizu

"&'ItS') E~j :t I ~[·4'; N

~ , .......

I L

j_

~-+--=~

1-+---~----f 01

I 1: \,.)

!!ll~e:.'!r ~~i·.czs:~ t l~a-~~N"f~

~:a (:I

= ~~ =.... '= r ~ti·1 :E ~~.,., B. t;' t: ~N H 1!. ~:11~

rrr:l !'F-l~

~~! UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL

J. r

f ~

COPlRIGHTED 1952 BY THE UNIVERSITY OF ILLINOIS SHALL HOMES COUNCIL. ALL RIGHTS RF.SERVED. Responsibility f or houses built from t hese drawings shall rest 11ith the user of t he dra11ings and in nollis e on t he University of Illinois. When variations from the original drallings are incorporated by the user, the structures built shall not be represented as being built from a des i gn develc.,ed through research at t. he University of Illinois.

Endorsement by the University of Illinois for any manufactured product shall not be claimed on the basis of these dra11i ngs or related information thereon.

Moditications Connections Modifications

to Pattern to Pattern

and and ~ ,. '

Member

~ Sizes

Cll

~ i ~ ' ..... 1:: ..a I ft~ ~I ~ 2 2 I

..... ~~+-~~~-4---------+~

i Cil~S"~ 00 - ~

~ '1 v- 'i"? ~ r;a.r ... m 1 'IE ,! 2 2 ~ ~ ~ N ~ g- ><:a

=--- tO~ ~ ~~~~~~------~~

a CilC.S'~ 0 0 p..

l\) ~ ~ab' .... ~ I "ta I 0 ~I~ f-1 .... 2: t-j

if ~ 2 g "-"' c+ ~ · .g ~ \a)

:a

~ , '

I ~ ~ 1-t

i ' ~ -

I~ ~ i L-~ N

I t_e'l?~ ~ ~ i~

L-~ ....

:) o~~~· ~t::~ t:;)' ~ I ._. I ~ I ~ ~ i 2

a ~

~ ~ ~ ~ ~~

Member

Sizes

:z: 0 lt-1 0 i ~~

~l\)Q()

SD = g I J:!: H itt i~g ~~SD~ -~ f tsNOO SD =go tJ"

~H a SD

~~tc& e: i•! I S" e

r

I r---- - I----_, I

I

g~~ § '3 ....

I

!• l\)

1: = H

F E

~ • g.~ . 8"t:P.. ~ ~ 1-'

!• l\)E c = ~ H ~ ~ N

=

0\

~

~

0

~

~

0\

~ I;!

~ UNIVERSITY OF ILLINOIS SMALL HOMES COUNCIL

LOAD TEST - "W" 'ffiUSS

A load test was conducted to determine whether the "W" truss was strong enough and rigid enough to carry the load for which it was designed--20 pounds per square foot, live load; or 30 o5 p os.f., total load.

For this test, five "W" trusses spanning 25 '-8'', out to out of the plates, were erected on single plates supported on concrete foundation walls.

The trusses were of No. 2 grade, or better, lumber. No special care was taken during fabrication. Trusses built on an actual job could be expected to be of equal or better strength.

The trusses, which were not braced in any manner during the testing, were sheathed with square-edged boards. Concrete blocks were placed on the sheathing, the trusses being loaded uniformly at approximately 20 p.s.f. for each increment of loading.

Deflection of the bottom chord was recorded for each loading.

The trusses collapsed due to failure of the top chords in the upper panels at a total imposed load of 128 p.s.f. This represents a factor of safety of 4.36 based on total loads. This is a satisfactory margin of safety since a 4.00 factor of safety is considered usual for wood.

The greatest deflection recorded for any truss at the design load of 20 p.s.f. was 5/16 inch and the average deflection for all trusses was approximately 1/8 inch.

On the basis of this test, the "W" truss is strong enough and rigid enough to carry, with a satisfactory safety factor, the load for which it was designed.

Tests are planned to measure the deflection of the truss under a longterm -loading. Since wood structures have a tendency to contin~e deflecting under a constant load, it is expected that trusses used on actual constructions would eventually deflect more under design loads than the value given above. This tendency, of course, is equa.lly true of any other method of roof construction.

-53-

ROOF TRUSS DESIGNS - IDEALS

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Transcript of ROOF TRUSS DESIGNS - IDEALS