A system for tighter wood-frame construction

Publisher’s version / Version de l'éditeur:

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.

Questions? Contact the NRC Publications Archive team at

PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.

https://publications-cnrc.canada.ca/fra/droits

L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.

Building Research Note, 1984-01

READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE. https://nrc-publications.canada.ca/eng/copyright

NRC Publications Archive Record / Notice des Archives des publications du CNRC :

https://nrc-publications.canada.ca/eng/view/object/?id=1d91a389-5254-48eb-accc-98d7bd93ace1 https://publications-cnrc.canada.ca/fra/voir/objet/?id=1d91a389-5254-48eb-accc-98d7bd93ace1

NRC Publications Archive

Archives des publications du CNRC

This publication could be one of several versions: author’s original, accepted manuscript or the publisher’s version. / La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version acceptée du manuscrit ou la version de l’éditeur.

For the publisher’s version, please access the DOI link below./ Pour consulter la version de l’éditeur, utilisez le lien DOI ci-dessous.

https://doi.org/10.4224/40000510

Access and use of this website and the material on it are subject to the Terms and Conditions set forth at

A system for tighter wood-frame construction

S e r

Tm

B92

A

SYSTEM FOR

G.O. Handegord

'

1

NATIONAL

A SYSTEM FOR TIGHTER WOOD-FRAME CONSTRUCTION

bf

G.O. Iiandegord

Ottawa January 1 9 8 4

A

SYSTEM

6 . 0 . Handegord

INTRODUCTION

Most c u r r e n t approaches to improving the airtightness of new wood-frame constructton concentrate on u s f n g a p l a s t i c f l l m vapour barrier a s an

air

construction and any u n n o t i c e d openlnge, t e a r s or gaps In the material are concealed by a p p l i c a t i o n of the i n t e r i o r f i n f s h . When the f Flm is n o t bonded La ar h e l d against t h e I n t e r i o r cladding or other s u p p o r t , air can

move l a t e r a l l y behind t h e i n t e r i o r Einish t o leak rhrough s u c h openings.

The

under a n air pressure difference. I f the airtightness of the e n c l o s u r e can

be achievcd i n some o t h e r way, the sealing of t h e s e gaps and joints is n o t

s o i m p o r t a n t and the plastic film might e v e n be replaced by some other form of vapour b a r r i e r .

Most of the primary a i r leakage p a t h s through the e x t e r i o r house envelope occur at opendngs through and around the i n t e r i o r cladding. T h i s Note describes a n approach t h a t u t t l l z e s t h e i n t e r i o r c l a d d i n g as the bartler t o a i r flow,

with

o r

c l a d d i n g elements. A somewhat similar a p p r o a c h was utilized i n the HUDAC Mark VII. project in 1 9 7 2 i n S u r r e y , B.C., where 9 - 5 3 mm ( 3 J 8 " ) f i r plywood was u s e d o n the ineide of wall and roof framing a s structural s h e a ~ h i n g and

as the a i r aad vapaur barrferm4

THE BASIC CONCEPT

The basic concept is illustrated in F i g u r e 1.

It

air

u t i l i z e s 12.5

rmn

p r o v i d e a s u r f a c e adjacent t o t h e interfor gypsum board so the butt joint can be filled wtth a sealant, wlth flextble adhesive tape or by the normal

applicatian of

drywall

A t upper floor intersections, j o i s t hangers ate suggested t o allow t h e 12.5 mm plywood to p r o v i d e vertical continuity

wtth

a l l o w for continuity t o be maintained when floors are cantilevered o u t w a r d

t o s u p p o r t upper w a l l s , as suggested fn the fnset of F i g u r e 1,

Although "storey h e i g h t " s t u d s or f u l l b a l l o o n framing could be employed, t h e framing system i l l u s t r a t e d In Figure 1 has some potential

advantages.

It

or

or

applied.

FOUNDATION WALL INTERSECTIONS

Box-Sill Method

F i g u r e 3 i l l u s t r a t e s an approach f o r the box-sill method where t h e

semi-box beam i s secured t o the outer h a l f of t h e foundation wall and t h e f l o o r j o f s t s s e t on a

38

sill

support for the edge of the s u k f l o o r .

The

has

spaces filled wirh f i b r o u s insulation, w f t h an additfond i n s u l a t i n g

sheathing a p p l i e d t o the exterfor of the studs. A t h i c k n e s s of f n s u l a t i o n equal t o the sheathing is shown extending down over the outer face of the foundation wall.

F i g u r e 4 i n d i c a t e s a suggested arrangement f o r a box-sill method utilizing brick veneer conetructkon wtth a 250 mm foundation wall. Preserved Woad Foundation

The semi-box beam approach could be used but c o n t i n u i t y c o u l d

be

If

will

i l l u s t r a t e d by t h e d o t t e d section between the f o u n d a t i o n wall studding.

TE

w a l l , t h i s may not be necessary.

" B e a m Fill" (Embedded Joist) Method

The semi-box beam could form t h e o u t e r t o p section of the foundation wall form work, w i t h the ends

of

INTERMEDIATE FLOOR-WALL

in

The semi-box

beam

floor

mm

the semi-box beam.

The t o p surface of the j o i s t is 25-35 mm below the t a p of the beam and the under surface of the joist is set above the bottom. The s u b f l o o r and

underlay a p p l i e d an top of the j o i s t should thus leave a portion of the plywood e x t e n d i n g upward

f o r

covered with 8 flexible p r e s s u r e s e n s i t i v e tape. The j o i n t would b e

concealed beneath t h e baseboard when tt is i n s t a l l e d . The j o i n t between the

lower edge of t h e semi-box beam and i n t e r i o r drywall m i g h t simply b e sealed by conventional drywall taping.

Offset f o r Brick Veneer

Figure 8 i l l u s t r a t e s a method f a r handlkng the o f f s e t requfred when brick veneer constmctian i s u s e d as c l a d d f n g for t h e _{first floor. A}

1 2 . 5 mm plywood s t r i p is installed on t o p of the upper wall p l a t e extending outward to t h e e n d s of t h e f o i s t s and i n w a r d s u f f i c i e n t l y to provide

continuity w i t h the drywall.

The

is

The l o a d i n g on these j o f s t hangers would be that due to roof loading and t h e

system would have to support t h e requfted loads.

A f l e x i b l e t a p e o r s e a l a n t could be utilized between the j o i s t s to

provide continuity f a r airtightness between Lhe horizontal 12.5 m e t h i c k

plywood s t r i p above t h e top plate and the plywood j o i s t header, but i t m i g h t best be utiltzed a t t h e o u r e r junction with t h e lower w a l l s h e a t h i n g .

Cantilevered F l o o r

Figure 9 i l l u s t r a t e s a method for the same system a p p l i e d t o aecond

floor wall intersections

where

lower wall and ceiling gypsum board c o u l d be s e a l e d In the conventional manner wlth j o i n t tape and

filler.

wALL/CEILING

No special d e t a l l f n g is suggested for the exterior w a l l and t o p f l o o r ceiling junctlon e i n c e

the

I n t e r i o r Partitions

F i g u r e 10b sllows a plywood s t r i p a p p l i e d t o the t o p p l a t e a£ the

p a r t i t i o n wall to p r a v i d e continuity across t h i s fntersectfan, The plywoad extends out beyond the plate 25 mrn or so to allow a base for a p p l i c a t i o n of

a f l e x f b l e t a p e or f o r t h e normal drywall t a p i n g and Eilllng operations.

EXTERIOR wALL/PARTLTION WALL

JUNCTION

A s i m i l a r d e t a i l could be arranged a t the e x t e r i o r wall/interior partition intersection, as in the plan v i e w of Figure 11; here t h e plywood s t r i p , n a i l e d ro t w o exterior wall studs, also acts as a s t r u c t u r a l tie. It w l l l provide continuity of t h e a i r b a r r i e r through the Intersection a s well as securing the intersecting

wall

with

WNI~BW/WALL JUNCTION

No s p e c i a l detafling would be required at the window but improved

airtightness might he obtained by sealing t h e j o i n t between the gypsm board and the window frame with a f l e x i b l e t a p e a f t e r packfng the clearance space with sealant o r tnsulation. This t a p e would subsequently be covered by the

window trfm as I n Figure 12.

ELECTRICAL

WIRING AND

PENETRATIONS

It

e x t e r i o r walls, t h e s e openings should be sealed t o mlnimize a i r leakage. Ourlet box locations on the exterior w a l l s could be sealed from the

interior, uaFng p l a s t i c f i l m or gasketed covers if these are deemed to be necessary.

The approach outlined i n this Note i n v o l v e s some changes I n current

p r a c t i c e s b u t is a d i r e c t a n d positive way t o p r o v i d e an accessCbPe

s t r u c t u r a l a i r

barrier

Suggested d e t a i l s u s i n g this approach are provided f o r d i f f e r e n t

l o c a t i o n s and intersections, wkth some consideration f o r d i f f e r e n t regional construction practices. No d o u b t other modifications can be d e v e l o p e d t o u t i l i z e specific local or r e g i o n a l requfrernents

,

Although adequate water vapour diffusion resistance (vapour barrier

requirements) can b e met through t h e application of s u i t a b l e i n t e r l o r paint or wallpaper after c o n s t r u c t i o n , there may be advantages to the use of w a l l b o a r d Incorporating a f a c t o r y - a p p l i e d vapour barrier. A l t h o u g h

38 x 89 mm s t u d s a r e shown, 38 x 140 mm framing members could he used to

allow added insulation, I n s u l a t e d sheathing or h o r i z o n t a l s t r a p p i n g c o u l d

allow increased t h i c k n e s s e s of insulation to be a p p l i e d .

F i g u r e 13 shows a one-half s c a l e m o d e l construcred to i l l u s t r a t e

application of the method t e various d e t a i l s . The help and a d v i c e o f

J . D . Scott of DBR in t h e development of t h e method and construction of t h e m o d e l was greatly appreciated.

REFERENCES

1, Energy Efficient Housing

-

Council, SRC No, E-825-2-E-81, Saskatoan, March 1981.

3. G.O. Nandegord, Vapour Barriers in Home Constructfan, Canadian Building

Digest No, 9, D i v i s i o n of BuiLding Research, Natianal Research Council Canada, Ottawa, September 1960.

4 . A.W. Kempthorne, Experimental Project Mark V I L , p r e p a r e d for Housing and Urban Development: A s s o c i a t i o n of Canada, Technical Research Cornmitree,

Toronto, July 1973.

5 . _{J.W. Lstiburek, The Drywall} Approach to Airtightness, Proceedings,

Second CSCE Conference on Building Science and Technology, llnivers ity of

F l G U R E 1

F I G U R E

2

F I G U R E

3

F I G U R E

₄

F I G U R E

5

F I G U R E

6

F I G U R E

7

S E C O N D

F L O O R

I N T E R S E C T I O N

-

F I G U R E

8

S E C O N D

F L O O R

W A L L I N T E R S E C T I O N

F I G U R E

9

F I G U R E

10

l a )

W A L L - C E I L I N G

D E T A I L :

I b )

P A R T I T I O N

W A L L - C E I L I N G

F I G U R E 11

P A R T I T I O N

E X T E R I O R W A L L I N T E R S E C T T O N

( H O R

I Z O N T A L S E C T I O N )

F I G U R E 1 2

W I N D O W

M U L L I O N

D E T A l

L

( H O R I Z O N T A L

S E C T I O N 1

( S I L L

A N D H E A D S I M I L A R 1

O N E - H A L F S C A L E

M O D E L

C O N S T R U C T E D

TO

I L L U S T R A T E