Fire resistance of gypsum board wall assemblies

(1)

Publisher’s version / Version de l'éditeur:

Construction Technology Update, 1997-01-01

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

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 [email protected].

Questions? Contact the NRC Publications Archive team at

[email protected]. If you wish to email the authors directly, please see the first page of the publication for their contact information.

NRC Publications Archive

Archives des publications du CNRC

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

Fire resistance of gypsum board wall assemblies

Sultan, M. A.; Lougheed, G. D.

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.

NRC Publications Record / Notice d'Archives des publications de CNRC:

https://nrc-publications.canada.ca/eng/view/object/?id=43daff2f-068f-499f-bd54-1342d275cc97 https://publications-cnrc.canada.ca/fra/voir/objet/?id=43daff2f-068f-499f-bd54-1342d275cc97

(2)

b y M.A . S ulta n a nd G.D. Loughe e d

This Update discusses the importance of various factors in achieving the required

fire resistance for w alls in multi-family dw ellings. The information is based on

results from an extensive industry-supported research project carried out by the

National Research Council’s Institute for Research in Construction (IRC).

1

C o n s t r u c t i o n T e c h n o l o g y U p d a t e N o . 2

Research ers at IRC set ou t to d eterm in e h ow th e sou n d tran sm ission class (STC) an d th e fire-resistan ce ratin gs (FRR) of in su lated an d n on -in su lated gyp su m board w all assem blies w ou ld be affected by tw o d ifferen t kin d s of ch an ges. First, n ew requ ire-m en ts in th e 1990 Nation al Bu ild in g Cod e of Can ad a (NBC) in creased th e STC betw een d w ellin g u n its from 45 to 50 an d secon d , th e stan d ard regu latin g th e u se of gyp su m board called for th e rem oval of m in im u m d en sity requ irem en ts for gyp su m board .

Wh ole system s, n ot ju st m aterials, w ere tested to get a com p lete p ictu re of h ow variou s p aram eters affect acoustic and fire performance, as th e ach ievem en t of h igh acou stic p erform an ce m ay h ave n egative im p lication s for fire p erfor-m an ce, or th e oth er w ay arou n d .

In th e fire testin g, th e assem blies w ere exp osed to h eat in a p rop an e-fired vertical fu rn ace. Each assem bly w as given a fire-resistan ce ratin g based on th e tim e it took to fail in an y w ay — stru ctu rally, or by exceed in g a sp ecified tem p eratu re, or p erm ittin g th e p en etration of flam es or gases h ot en ou gh to ign ite cotton w aste.2

I nflue nc e of Va rious Fa c t ors on Fire Re sist a nc e

Th e in flu en ce of th e variou s p aram eters (see box, p age 2) are as follow s:

Type of Gypsum Board

Gyp su m board w ith glass fibre in th e gyp su m core p rovid es better fire resistan ce th an gyp su m board w ith ou t glass fibre. Th is is d u e to th e fact th at th e ligh ter th e gyp su m board is, th e m ore easily it cracks; an d th e m ore cracks it h as, th e m ore su scep tible it is to disintegration in a fire. The glass fibre in the core helps keep the gypsum board togeth er. Wh en th ere is m ore th an on e layer of gyp su m board on each sid e of th e assem bly, th e p resen ce of glass fibre in th e gyp su m core h as less effect.

In load -bearin g assem blies w ith ligh t-w eigh t regu lar gyp su m board , th e p resen ce of th e glass fibre in th e gyp su m board core in creased th e fire-resistan ce ratin g of an assem bly w ith a sin gle layer of gyp su m board (w ith a d en sity of 7.35 kg/ m2_{) on} each sid e by 25 p ercen t com p ared to th e sam e sin gle-layer assem bly w ith n o glass fibre in th e gyp su m core (w ith a d en sity of 7.27 kg/ m2_).

Density of Gypsum Board

Th e fire resistan ce of w all assem blies w ith regu lar (stan d ard ) gyp su m board in creases as th e d en sity of th e gyp su m board in creases.

Wh en n on -load -bearin g assem blies w ith a d ou ble layer of regu lar gyp su m board on each sid e (2x2) w ere tested , an assem bly w ith gyp su m board of a h igh er d en sity (7.82-kg/ m2_{) p rovid ed a sligh tly better}

Fire Resistance of Gypsum

Board Wall Assemblies

Figure 1. A gypsum board wall assembly undergoing testing in IRC’s propane-fired vertical furnace.

(3)

2

fire-resistan ce ratin g th an an assem bly w ith gyp su m board of a low er d en sity (7.35-kg/ m2_).

Number and Arrangement of Gypsum Board Layers

In creasin g th e n u m ber of layers on each sid e from on e to tw o im p roves th e FRR.

Usin g an asym m etrical assem bly (1x2), h ow ever, offers n o p articu lar ad van tage over th at of a sym m etrical (1x1) assem bly for a load -bearin g w all assem bly sin ce it m u st be assu m ed th at th e fire w ill start on th e sin gle-layer (w eakest) sid e.3 _{Th u s, th e} fire-resistan ce ratin g for an asym m etrical (1x2) assem bly is com p arable to th at of th e sym m etrical (1x1) assem bly. Wh ile th e asym m etrical arran gem en t can h elp ach ieve a h igh er STC, it d oes n ot im p rove th e FRR.

In load -bearin g (w ood ) assem blies w ith glass fibre in su lation in th e w all cavity an d w ith resilien t ch an n els, a sym m etrical assem bly w ith a d ou ble layer of 12.7-m m th ick gyp su m board (2x2) p rovid ed a 55-p ercen t in crease in th e FRR as com p ared to an asym m etrical (1x2) assem bly.

Thickness of Gypsum Board

In creasin g th e th ickn ess of th e gyp su m board layer d oes n ot ap p ear to im p rove th e FRR w h en resilien t ch an n els are p resen t on th e sin gle-layer sid e.

Wh en load bearin g asym m etrical assem -blies (1x2) w ith glass fibre in su lation in th e w all cavity an d resilien t ch an n els located on th e sid e w ith th e sin gle layer of gyp su m board (fire-exp osed sid e) w ere tested , ch an gin g th e Typ e-X gyp su m board th ickn ess The project investigated the effects of the following parameters on the fire resistance of 22 wall assemblies:

Symmetrical and asymmetrical arrangements of gypsum board. Th ree d ifferen t w all assem bly arran gem en ts on w ood stu d s an d on ligh tw eigh t-steel stu d s w ere stu d ied :

• sym m etrical in stallation (1x1) — on e layer of gyp su m board on both th e fire-exp osed an d u n exp osed sid es

• asym m etrical in stallation (1x2) — on e layer of gyp su m board on th e exp osed sid e an d tw o layers of gyp su m board on th e u n exp osed sid e. For all tests p erform ed on asym m etrical assem blies, th e sid e of th e w all w ith th e sin gle layer of gyp su m board w as exp osed to fire sin ce th is is th e m ore con servative orien tation .

• sym m etrical in stallation (2x2) — tw o layers of gyp su m board on each sid e.

Type, density and thickness of gypsum board. Tw o gyp su m board typ es w ere evalu ated :

• Typ e-X, w h ich is a gen eric n am e u sed to d esign ate gyp su m board w ith a sp ecially form u lated core th at p rovid es a greater fire resistan ce th an regu lar gyp su m board . Both 12.7-m m an d

15.9-m m th ickn esses w ere tested .

• Regu lar gyp su m board , 12.7 m m th ick w ith d en sities (m ass p er u n it area) of: 7.82 kg/ m2_{w ith n o glass fibre in th e gyp su m core}

7.35 kg/ m2_{w ith glass fibre in th e gyp su m core. (Th is ligh tw eigh t gyp su m board w as} m an u factu red sp ecifically for th is p roject.)

7.27 kg/ m2_{w ith n o glass fibre in th e gyp su m core.}

Both typ es con form ed to CAN/ CSA.A82.27-M91, th e stan d ard regu latin g th e u se an d ap p lication of gyp su m board .

Resilient channel installation. A resilien t ch an n el is a lon g strip of th in steel w ith a step p ed con figu -ration w h ere on e vertical leg is attach ed to th e stu d an d th e oth er to th e gyp su m board ; it h as a total w id th of abou t 25 m m . Resilien t ch an n els w ere attach ed h orizon tally on eith er th e fire-exp osed sid e or th e u n exp osed sid e, sp aced at 400 m m on cen tre p erp en d icu lar to th e w ood stu d s. Th e gyp su m board w as th en attach ed to th e resilien t ch an n els. Th e p u rp ose of th ese ch an n els is to p rovid e a d iscon tin u ity so th at sou n d is less able to be tran sm itted th rou gh th e assem bly.

Type of insulation. Glass fibre, rock fibre, an d cellu lose fibre in su lation w ere tested .

Stud type and arrangement. The wood-stud walls tested included both load-bearing and non-load-bearing assem blies, alth ou gh all steel-stu d w alls tested w ere n on -load -bearin g. Th e w ood -stu d con figu ration s in clu d ed sin gle, d ou ble an d staggered row s. A sin gle p late w as u sed for assem blies w ith sin gle an d staggered stu d s an d d ou ble p lates w ere u sed for assem blies w ith d ou ble stu d s.

(4)

3

• one or two layers of gypsum board • 38-mm x 89-mm studs

• with or without absorptive material • one or two layers of gypsum board

• one or two layers of gypsum board • two rows 38-mm x 89-mm studs staggered on common 38-mm x 140-mm plate

• with or without absorptive material • resilient channels

• one or two layers of gypsum board

• one or two layers of gypsum board • 31-mm x 64-mm

non-load-bearing studs

• one or two layers of gypsum board • 31-mm x 92-mm steel studs • with or without absorptive material • one or two layers of gypsum board • one or two layers of gypsum board • two rows 38-mm x 89-mm studs on separate 38-mm x 89-mm plates set 25 mm apart

• with or without absorptive material • one or two layers of gypsum board • one or two layers of gypsum board • 38-mm x 89-mm studs

• with or without absorptive material • resilient channels on one side • one or two layers of gypsum board 1 layer both sides 2 layers 1 layer 2 layers both sides 400 mm 1 layer 2 layers 89 mm a) b) c) d)

Wall construction 1. Single wood studs

1 layer both sides 2 layers 1 layer 2 layers both sides 400 mm 1 layer 2 layers 102 mm a) b) c) d)

Wall construction 2. Single wood studs with resilient channels

2 layers 1 layer 2 layers both sides 1 layer both sides 400 mm 140 mm a) b) c)

Wall construction 3. Staggered wood studs

153 mm 2 layers 1 layer 2 layers both sides 1 layer both sides 400 mm a) b) c)

Wall construction 4. Staggered wood studs with resilient channels

Wall construction 5. Double wood studs

Wall construction 6. Non-load-bearing steel studs (64mm)

1 layer both sides 600 mm 2 layers 1 layer 2 layers both sides 92 mm a) b) c)

Wall construction 7. Non-load-bearing steel studs (92mm) Wall construction 1. Single wood studs

Wall construction 2. Single wood studs with resilient channels

Wall construction 3. Staggered wood studs

Wall construction 4. Staggered wood studs with resilient channels

Wall construction 5. Double wood studs

Wall construction 6. Non-load-bearing steel studs (64 mm)

Wall construction 7. Non-load-bearing steel studs (92 mm) Ba sic Wa ll Configura t ions Te st e d

(5)

from 12.7 m m to 15.9 m m d id n ot im p rove th e fire-resistan ce ratin g. How ever, th e fact th at th e fire-resistan ce ratin g d id n ot im p rove w ith th e in creased th ickn ess w as m ain ly d u e to th e ign ition of th e w ood stu d s, cau sed by th e p en etration of th e h ot gases th rou gh th e u n p rotected gyp su m board bu tt join ts. Th e gap betw een th e stu d s an d th e gyp su m board , created by th e p resen ce of th e resilien t ch an n els, acted as a p assagew ay th rou gh w h ich th e flam es an d h ot gases sp read after en terin g th e cavity.

Wh en resilien t ch an n els are n ot u sed , th e FRR of th e sam e assem bly can be im p roved from 25 m in u tes to 40 m in u tes by in creasin g th e th ickn ess of Typ e-X gyp su m board from 12.7 m m to 15.9 m m .

Installation of Resilient Channels

In som e cases, resilien t ch an n els can h elp to im p rove th e fire resistan ce of th e assem bly; h ow ever, locatin g th ese ch an n els on th e sin gle-layer sid e m ay sign ifican tly d ecrease th e fire resistan ce of th e assem bly.

In th e asym m etrical (1x2) load -bearin g assem blies w ith rock fibre in su lation an d resilient channels, the assembly with resilient ch an n els in stalled on th e d ou ble-layer sid e p rovid ed an 11-p ercen t better fire-resistan ce ratin g th an th e sam e assem bly w ith resilien t ch an n els in stalled on th e sin gle-layer (fire-exp osed ) sid e.

Type and Installation of Insulation

Rock fibre in su lation in stalled in th e cavity of th e w all assem bly con tribu tes sign ifican tly to its fire resistan ce. To m axim ize th e ben efits of in su lation on th e fire-resistan ce ratin g, it is im p ortan t to in stall th e in su lation tigh tly betw een th e stu d s.

Wh en th e rock fibre in su lation w as in stalled in n on -load -bearin g assem blies in th is w ay, it p rovid ed a 60-p ercen t better fire-resistance rating (100 minutes) than when it was installed loosely (60 minutes).

In n on -load -bearin g asym m etrical (1x2) steel-stu d assem blies, th e in stallation of eith er glass fibre or cellu lose fibre (w et sp rayed ) in su lation d id n ot affect th e fire-resistan ce ratin g.

Type of Stud

Th e typ e of stu d u sed in n on -load -bearin g w alls is in sign ifican t for assem blies w ith tw o layers of gyp su m board on each sid e.

In n on -load -bearin g assem blies w ith a d ou ble layer of gyp su m board on each sid e (2x2), th e assem bly w ith w ood stu d s p rovid ed a sligh tly better fire-resistan ce ratin g th an assem blies w ith steel stu d s. (Assem blies w ith on e layer of gyp su m board on each sid e w ere n ot tested , becau se th ey d id n ot m eet STC criteria.)

Arrangement of Studs

Th ere are n o p articu lar ben efits in term s of fire p erform an ce in u sin g staggered stu d s or d ou ble stu d s in stead of sin gle stu d s, alth ou gh th ese con figu ration s can h elp en h an ce acou stic p erform an ce.

I m pa c t on t he I ndust ry

As a resu lt of th is p roject an d th e related p roject by IRC’s Acou stics Laboratory on th e STC of w all assem blies, th e fire- an d sou n d -resistan ce ratin gs of w all assem blies in Part 9 of th e 1995 NBC h ave been u p d ated an d au gm en ted from 17 listed assem blies in th e 1990 Cod e to over 160 in th e 1995 Cod e.

Drs. M.A . S ulta nan d G.D. Loughe e d are sen ior fire research officers in th e N ation al Fire Laboratory of th e N ation al Research Cou n cil’s In stitu te for Research in Con stru ction .

1. Th e p roject w as su p p orted by a con sortiu m th at in clu d ed Can ad a Mortgage an d Hou sin g Corp oration (CMHC), Can ad ian Sh eet Steel Bu ild in g In stitu te (CSSBI), Cellu lose In su lation Man u factu rers Association of Can ad a (CIMAC), Forin tek Can ad a, Gyp su m Man u factu rers of Can ad a (GMC), IRC, Ow en s Corn in g Fiberglas Can ad a In c., an d Roxu l In c.

2. Sin ce th e NBC stip u lates th e requ ired fire-resis-tan ce ratin g as w ell as th e typ e of con stru ction th at an assem bly u sed in a p articu lar occu p an cy an d location m u st h ave, an d sin ce th ere are n o fire-resistan ce ratin gs of less th an 45 m in u tes in clu d ed in th e Cod e, assem blies th at h ad a FRR of less th an 45 m in u tes w ere con sid ered to h ave failed . 3. How ever, for a n on -load -bearin g assem bly, a 1x2

assem bly p rovid es a better fire resistan ce th an a 1x1 assem bly.

“Construction Te chnology Up d a te s” is a se rie s of te chnica l a rticle s conta ining p ra ctica l inform a tion d istille d from re ce nt construction re se a rch.

For more information, contact Institute for Research in Construction, National Research Council of Canada, Ottaw a K1A 0R6

Nation al Research Cou n cil of Can ad a Jan u ary 1997