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NATIONAI RESEANCH COU}ICII OT' CAJ{ADA NIVISION OF BUIIDING ITESEARCH
FIRE StrPARATIO}IS II.T fHE
NArrolrAt BurrDrlIG coDE (1951)
by
J . N . K a t n i c k a n d R . S ' F e r g u s o n
A T { A L Y Z E D
Iechnical Paper No. 50
of the
nivislon of Buildlng Research
OTTAWA
FRONTTSPTECE
ftris photograph shows a mod.el of an elementary school pre-pared by J.N. I(atnick in conjunction with his studies leading to the preparation of thj-s report.
TLre nod.eI shows by colour the applicatlon of fire separation requlrements in the National Bullding Cod.e as these are related. to school build.ings. Different degrees of fire reslstance are shown by different colours; elenents of the building requi-ring no fire resistance are shown in clear plastic.
Ttrls nodel has been dlsplayed at severaL meetlngs and has stinulated thought and diseussion. ft has helped ln galning a wider appreciation of the flre requirements in the Code, and, has also led to constructi.ve sug8estions on how they might be improved.
It ls hoped that this lnterest w111 contlnue to Brow as it ls an essentlal lnrt of the d.eveloproent of adequate flre require-ments for bulldlngs in Canada. Desplte rapid technologi-caI change this public interest can effect suffloient reform in fire regulations to ensure safety wlthout d.eprivlng the publlc of the taaqy beneflts that the new technology has to offer.
PREFACE
Iflhen the National Bui]ding Cod.e was revised. ln 1953 the regulatlons for the prevention of fire spread. were con-pletely revrrrj-tten in a for:m and language more suitable to the regulation of architecture and buildi-ng tod.ay. In accepting a nerr approach based on recent theorles in fire
engineering, the Assoclate Conmittee anticipated. that a higher degree of safetJ' woul,l be possible at less cos'b
to the ovmer and with less restriction on design expression. It was realized, however, that a eompromise had to be mad.e with the ideal approach in ord.er not to effect,too Ereat a
d.eparture frora current practi.ce.
E\ren the best regulati.ons are of littIe value if they are not clearly understoorl. this report has been prepared as an explanation of the regulations so that mis-understandings arising from their use will be lessened. J.N. IGtnick, architectural student at the University of Brj-tish Columbia, prepared this report while on the staff of the Divi.sion thls past sultrmer. R. S. Ferguson, Secretary of the Associate Connnittee on the National Building Code,
6uided his investigations.
ftrls paper, while answering some questlons, will undoubtedly ralse others. It is hoped. that, through the comments and. suggestions of readers, whi-ch wlll be welcomed, the fire regulatlons in the Natj.onal Builcling Code can be still further i.mproved.
Ottalva
April 1958
Robert F. legget Director
TASIE OF CONTENSS 2 2 4 2 . Paqg
1 . DE\TET,OPMEIIf OI' IgE SCIEIqCE OF FIRE PROTECIION
( a ) R e g g a r c h W o r k . . . r . . . . . . e . . . r . . . ( b ) F l r g R g s l s t a n c g f g s t s . ) . . . o o . . . .
(c) Orema1 Radiatlon from Burnlng Buildtngs .. o,,
I H E N A r I o l I a l B U I I D I N G C O D E . . . , . . . 6 ( a ) F i r e R e g u l a t l o n s . . o . . . 6 ( b ) F l r e S e p a r a t l o n s D e f i n e d . . . . . ' l ( c ) G r a d i n g and Requirenents of S e p a r a t i o n s ... 7 ( d ) F i r e S e p a r a t i - o n B e t y r e e n B u i l d i n g s ... . o.. .. . 10 ( e ) S e p a r a t i o n b y T i r e W a l l s . . . 1 2 ( f ) F i r e S e p a r a t l o n W i t h i n B u i l d i n 6 s . . . o . . . , . . 1 5 3 . C O I i I C I U S I O N .. . o . . . o . r . o . . . o o . . . . . 1 6
FIRE SEPANATIONS
rN fTrE NAlroNAt BUTTDINq qO!4L1_9,51.
by
J . N . K a t n l c k a n d R . S " F e r g u s o n
Records show that a large proportlon of Anerlcan and Canadlan cities have been subjected to a conflagratlon at some time during their history. Ihese conflagrations started un-pretentiously as tloes alnost every fire. Slnee there was usually very Ilttle resistance given to the flre, however, it spread' uncontrolled from bullding to building, laying waste large areast sapping the economy of the city, and causing a tragic loss of l i f e .
1. DE'TIEIOPMENT OF trTE SCIENCE OF FIRE PROIECTION
As a result of these early conflagratlons, regulations to limlt the use of materlals that presented a potential flre hazard were d.eveloped and grad.ually the practice of reguiring more solLd trfireproofrt construction spread., partieularly in the congested districts which were usually the victlrns of such conflagrations. Despite attenpts to combat then, conflagrations continuecl and so-caIled fireproof bulldings were gutted along with the rest. Grad.ually fire departnents became more effici.entt water supply was lmproved., and. more effective nethods of
con-struction to prevent fire spread were developed.. In ti-me
hrowled,ge of llre behavlour and fire defence became more refined and the general problem of the holocaust could be countered by speciallzed" precautj-ons against better-defined .hazards. Wlth t6e aid of laboratory research, ways of measuring fire lntenslties and the effecti.veness of protection were devised. Tlris field of knowlecLge is becoming lorown as fire englneering.
It is largely upon the new knowledge of flre elglnee"ln€; that the fire requlrements of the National Buildlng Code are based. Ihe requirenents are a refinement over previous regula-tions and make possi.ble the d.esign of buildings whlch have greater fire sifety provided at less cost than has prewiously been possi.ble. A.n understand.ing of the tersns used. and the functions that have been developed. as a result of research is deslrable if these regulatlons are to be applied" to best advan-tage. Ttle next few paragraphs describe the fire research ancl fiie engineering that apply. A full dlscussion of the flre seBaration requjrements-of tfre National Building Code follows.
2 (a) Research llork
Smong the earllest research lnto flre was that of the E[re Offlcest Comnlttee fo:med ln Brltaln in 1858. fhls
Coruntttee became the Brttish Fj.re Prevention Connlttee ln IB97 (1). Its najor task was to perforu tests so that d.ata coneerai.ng the flre resistanee of varlous materials and systems of
con-struction usecl ln bullctlng practice could'be conplleil, and that lnrtlculars conceruing flre preventlve, ftre aLa:m, or flre
extlnguishlng appli.ances coul-d. be collected. By the end of the century maqy dlfferent naterials hacl been subjected. to these tests, and tables for asslstance to bullders bad been drawn up reoording the flre reslstance of floors, celllngs, d.oors, prbltions and the Ilke.
In the Unitecl States, due to the Large number of cllsastrous fires, the Underwrltersf Ieboratories Incorporated was formed, in l.B9+ by a group of Anerlean lnsurance companies
(2). Its fuuction was slnllar to the Brltish ELre ?reventlon Commlttee. Varlous types of equipment, applLances ancl materlals were tested to meet safe stantlard.s of flre practlce. T]ris
organJ zatlon also publlshecl llsts of products that were tested and. found. acceptabLe.
Ifueh of the natertal gathered by these early assoclatlons has been superseded by later developmeats; the prlnclples
fomulated. prove vaLld tod.ay, however, and, ln nany cases, have fo:med. a valuable foundatlon for later research.
(b) Pire Resistance Sestq
In the course of tlne, lnvestlgatlons into the flre reslstlvity of naterlals Ied to the d.eveJ.opment of stanclards for sompring the results of tests of different klnds of com-lnnents canied. out by dlfferent organlzatlons ln dlfferent pJ.aces, and ln both r:rnglancl aad the Unltecl States pe:manent testlng statlons were set up by the gove:mment. Standard. fur-nsces aacl testlng proeed.ures were cleveLoped, so that materials could be tested uncler conditlons closely approxlnatins those of actual practlce. fhe stand.ard.s for tests are reasonably compar-abLe betweea countrles, and w111 become more so as thls techni.que clevelops. lEhe extent to whlch waLLs, columns, floors, and types of constmction are able to wlthstand fire 1s record.ed by these tests. llhe American Society for Iestlng ldater"Lals, has
pre-scribed nethods which measure and. speclfX, accordlng to a common stanclard., the flre reslstlve propertles of materlal,s anct
assemblles. ftrls standard. ls appllcable to a wid,e variety of naterlals, sJ.tuatlons, and. condltlons of exposure (5r.
- 1
It is lnteresting to note how a butlding conponent is subjected to fire condttions in a fire reslstance test. fhe principal element that an assenbly nust resist ls heat; therefore, furnaces are desi&red so that the object tested forms a walI of the fire box. Ttms the heat is distributed, over the surface of the assembly. ILle dlmensj-ons of the sample tested. compare wlth building uni.ts such as wall or floq panels and the sample can be subjected. to whatever loads lt would carry ln a bullding" The temperature ln the furnaee is controlled to an agreed-upon rate of rlse durin6 the period of the test. This relationsirip between temperature rise and time is knovrn as the time-temperature curve, whlch is shown graphieally 1r Flg" 1. fltris curve repre-sents the conditlons which may occur 1n a severe fire, Any specimen, therefore, whlch j.s subjected to the test and. achleves a rating in hours or mj.nutes can, with reason, be expeeted. to
last for the same length of time under si.milar flre con<litions ln a building.
It is evident that an assembly of materials that can wlthstand. a stand.ard flre-resistance test for a period. of three hours is subjeeted to more heat than is an assernbly that can withstand. a test for one hour, and to produce thls heat more
fuel 1s consumed.. TLre fuel used, and hence the heat prod,uced in the tests can be measured.. Ihe amount of fuel used when a sample fails gives sone idea of the amount of combustibles that could burn before that assembly will fail, if erected. in a bulldlng. flre next step was to d.ete:mine the amount of com-bustj.bles in different types of buildi-ngs. Slhen thls was ]anom it was posslble to recommend the d,egree of fire resistance
required. to urithstand, a bur:r-out of the contents of di-lferent bui.ldlngs.
truire load. Conce Dr. S.H. Ingberg of the Natlonal Bureau of was the pioneer whose studies led to measur&ble relationships betuveen the fire resistanee dete::mlned ln tests and the fire reststance necessary in bulldings (4). ft was found that the temperatures attained at certain ti.me lntervals and the amount of fuel burned in the standard fire reslstance tests Frere related. From repeated tests it was dlscovered that fuel equivaS-ent to 10, 20, 10, and. JJ pounds per square foot of floor area was burned duri.ng the standard. fire test at the end of Lr 21 3, and. 4 hours respectively. I?rus the fueL used to ralse the tenperature to 17O0oF. at the end of one hour would be equivalent to a fire load of 1O pound.s of conbustibl,es per
square foot of floor area. To attain a temperature of 185O"F. at the end of two hours, fuel equivalent to 20 pounds per squ;l?e foot would be needed.. By using 10 pounds per square foot as the value to produce a flre lntensity of 1700"F. a margln of safety ls provided because actually an intensity of UOOoF. is produced by burning eombustibles equtvalent to 12 pounds per s q u a r e foot.
- 4
It seems true, at least hypothetically, that if a building contai-nin8 a lO-pound fire load was bullt of elenents having a one-hour fire rati-ng it couId just stand a burn-out wlthout collapsing. By the use of the relationshlp between the
eombustible contents of a bu11din6 and the fire resistance there is reasonable assurance that any assembly of rnaterlals receivlng a 1-, 2- r or ]-hour ratl.ng could withstand complete content burn-out of a bullding wlth a 10-, 2O-r or 5O-pound fire load respectively. Ihris fire Load eoncept permlts the appllcatlon o f a d e q u a t e , but not excessive, fire resistance to a buildi:ig when the weight of its combustj.ble contents are lorown"
To obtain data on actual fire loads 1n buildin6s, surveys of buildings were made ln which the combustlble contents were wei6hed and recorded. Ttris work was done 1ar6e1y by the Bureau
of Standards ln washj-n6ton, D.c, (5). ftre weight of combustibles ls measured in pound.s per square foot just as is the live load. In fact the flre load i-s the live l-oad. but only of the combustibl,e contents. It ls not unnatural, therefore, that it shouLd be
call.ed the ttflre load.tt.
When it is said that an assembly having a flre reslstance of one hour wlthstancls a burn-out of contents equal to a 10-pound fire load thls relatlonship is a convenient approximation and is aclequate for practical purposes. It should not be for-gotten, however, that combustibles burn at different rates and some release more heat than others. For practical purposes all solLds can be regarded as havlng the same calorific value as p a p e r o r w o o d , 1 . e . , 71000 to B'0OO Bturs per pound of materlal. Rou6hly speaklng all liquids can be regard.ed. as having a calorlfic val-tre of doubl-e that of wood. A fire ln a palnt shop or hard-ware store can be expected to be more intense than in a dry good.s
establj-shment. In the Nati-onal Building Code these differences are dealt with ln the occupancy classificatlon.
(c) Ttrernal Ractiation from Burnire- Buillircg
Erom the foregolng d.iscussion the terms fi,tg load and fire resistance ar:e estaflished and the relationffilii-b?ffieen
the turo is lndicated. In addltion to these two elements it is necessary to recognize the signiflcance of space for a fu1l apprecJ.atlon of the fire requirements of the NationaL Building Code. Extenslve stud.les on thermal radiation from burning buildlngs were perforrned recently in Great Britain. trbom this research it was possible, to some extent, to determlne what distance betmieen bu11d1n6s would give sufficient safety to one building from thenoal radj,atlon from another. Ihe lntenslty of heat radiated from a burrring bui-lding to another building d.epends on many factors:
5
(1) flre wind.ow area and the dirnensions of the elevation of the building;
(lf ) Ore absol-ute temperature of the radia.ting surface (directly related to the flre load of the builriing) and its enissivity;
(iil) ttre distance betrrreen the buildlngs,
It rnay be assumecl, ln general, that the degree of themal rad.i.ation 1s inversely proportional to the square of the ctis-tance between opposin6 facad.es.
For a detailed account of thermal radiation the read.er is referred to rrrnvestigations on Building Flrestr (6). This sqne parophlet includes tabl-es which inilicate the reLationship of fj-re radiation to height and length of bulld.ings, the
distance betnareen buildi.ngs, and the slze and number of window openings. By the use of these tables approximate caleulations for dlstances between bulldings to overcome radiation effects c a n be made.
Several assumptions affecting the rellabil-ity of these tables had to be made when collecting the data. rtreie werel
(1) ftrat the tenperature of the rad.iatin8 flre is
1rO00oC (1Bl2oF). (varlatlons from tnf s tempe::ature would cause najor differences because the inten"sity of rad.iation ls directly proportlonal to the fourth power of the absolute temperature of the radiating surface ) ;
(1i) "&rat the emlssivity of the fire ls constant; and (lii ) That heat ls belng rad.iated. from all openi_ngs
slmultaneously.
Ttris last assunption ls highly lmprobable for a number of reasons. Elrstly, the flre resistance of the construction whj.ch would enclose a flre within small conpartments would. hinder lotgl conflagration. Second1y, the conbustlble contents of the buildln8s are not the same throughout and its i6nitabltity and rate of burnlng would limit flre spread, ttrirdly, fj-re flghtlng would have a si-gnlficant effect on both the seveiity of the fire and the rate of its spread. lllhen conslderin8 these- facts, lt 1s apparent that the tables in the publication were compiied from data collected durlng extreme fire conditlons. Conditions p_robably would not become so extreme 1n an actual fire and, therefore, the dlstances required for safety woulct not be-so g r e a t .
6
2. ffiE NATIONAI BUTIDI}IG CODE OT CA].IANA
ftre Natlonal Buildlng Cod,e of Canadr'ro"s first publlshed ln 1941 und.er the ausplces of the Deparbnent of Flnance and the Natlonal Research Councll. As bul1din6 techniques changed and new materi,als were introd.uced thts early edj-tlon of the Code
becaue outmoded and ln many instances was unnecessarlly restric-tLve. TLre fj.re regulatlons, partlcularly, did not meet the problerns presented in contemporary buildlngs nor dld the-v incorporate the advances made ln flre en6lneering. Yrlhen re-vision of the Cod.e began ln 1948, studies were made to improve 1t. ft was lmperatJ-ve that the revlsed cod.e shoulil not restrlct materials and types of constructlon and that 1ts form should
pemit subsequent revislons.
An entlrely new arrangement for the Code was developed treating general regulrenents flrst, followed by more detailed and speeiflc clauses. fhese a6aln were dlvlded into the general and speclflc wherever necessary. Cornmlttees and panels were
established to prepare d.rafts of the different parts and sec-tions. Under the Use and Occupancy Comnittee, four pane}s were set up to consid.er requirements for flre, health, exit and live l o a d s .
(a) Fire Regulations
The requirements of the flre regulations in the 1941 Cod.e were carefully consiciered by the Flre Fanel and whenever they
proved inad.equate or unnecessar1r by developments in flre engineerlng they were rerrised and inproved. fhe flre load. eoncept was studlied and finally accepted as the best method avallable for gauglng
the relative severity of flre in different occupanci-es, and as the criterion for determlning the fire resistance need.ed.
TLre consistency of flre regulations i.n the Natlonal
Bullding Code was achieved. through the adoptlon of the flre load of bulldings as the criterion for d.ete:mintng fire safety re-quirements. Ttre sunrey of the National Bureau of Standard.s (5) made it posslbLe for the Fire ?anel to classify occupancies of buj-ldings into groups ancl. di.vislons accord.ing to sinllarlty of function and extent of hazard. - thls classiflcation is found in Sectlon 3.2 of Pafi 7z Use and Occupaney - and then to
tabulate these uses according to their appropriate fj-re loacls in Tab1e 3.I. Ttrls flre load. classiflcation foms the basis for furtheri regulatLons.
fhe primary firnctions of all flre regulatlons are two-fold: to save ltv-es and to prevent the spread of fire. In ord.er to save lives sufflclent flre exlts from a buildlng must be supplied. Io create a maxlmum of Llfe safety fires must be controlled, their spread retarded., and the transfer o! heatt 6osr and siroke nul]iflecl. One method. of controlllng fires ls by adequate flre separatlons which would conflne fires withln a llrnited area setting up a barzier to the transfer of all hazard.s caused. by a fire.
7
(b) Flre Separatlons DeflnedTtre Natlonal Bullding Code , Patl 2, defines a separation as follows:
tfSeparation means a barrler against the spread of fire between Luildines or parts of bulldings in the {o* of flre-resistlve constiUctlon, or of clear unobstmctecl space as n"asurea by the dlstan6e across such.spacer oT of a comblna-tion of Uottr construccomblna-tion and space ' ft
flris deflnition is important. It establ-lshes tuvo klnds of separations constru6tlon anct space..- ft shoulil also be noted that these are aLte:nratives, since ei-ther a construction or a space separation can be us6d between buildtngs.- It is obvious that constmction separations only can be used' when separating areas within a-building. .Another alternatlve which is allowed' for separation U"toou"n-buildings is.a conbination of a construc-tio"-siparation with a space s6paration, so arranged that the sun of ihe protection pr6vltted is gqual to the grale.of separa-t i o "
" " q o i " 6 a i n T a b l e 3.7 referred-to
i n A r t i c l e 3 . 4 . 5 . I o f the Cocie.
The acceptance of space as all.-equivalent !o construction is a novelty of ine new National Butlding Code. - The-assunption is that a specified distance separation measured' in feet 1s the equlvalent of a construction
r e s i s f , a n c e i n h o u r s ( t r ' i g . 2 \ . I same safety will be provicl'ecl for resistlve barrier acljacent to th wlth no barrier.
(c) Grading and Requirengnts gf SePgfati,ons.
As pointecl out there is a relationship betrryeen intensity of fire and fire reslstance and also between intensity ?+d-its disslpatfon wiin distance. ILte committee was able to obtaj'n q"iiE-".fiaUf" d.ata on wtrich-a p'a'cti""1 decision could be made dnd it was agreed that the equivalent should be:
Distance Constnrctlon
3 0
40
5o
f e e t e q u t v a l e n t t o . . o - . . . ' . . l - h o u r f i r e r e s j - s t a n c e f e e t e q u i v a l e n t t o . . . 2 - h o u r s f i r e r e s i s t a n c e f e e t e q u l v a l e n t t o . . . o . J - h o u r s f i r e r e s i s t a n c e' 8
Tkre values shorrn in the Code for separatlon by space are half these d.istances because in the critl,cal case, 1.e., two adjacent bulldings wlth no exterior fire-reslstive wa1ls'_!h9 re{utred separation is obtalned if one-ha1f the reqqd.red dlstance is -provltted by each buildlng. Iherefore space separatlons are classifled. tnto three grailes:
Grad.e Dlstance
G r a d g ] - . . . o . . . ' . . 1 5 f g g t G r a d g 2 . . . o . r . . ' . . ' . 2 0 f e g t G r a d . g 3 . . . o o . . . o . o 2 5 f e e t
Srese dlstances are to be measured from the property llne to the waII of a buildirrg, fhus space separatlons, li.ke construc-tion separations, are-lnd.ependent of the neighbouring bu1lding.
llLre use of space separatlons allows unprotected openittgg. to be used and the-exterlbr walI need. not be-fire resistive (lt nust be non-coubustible wheu non-combustible constructlon ls used). By space, a clear space ln inferred, wlthout sheds or nrbbish whlch would have a wicklng action betlveen
bulldings-It must be emphaslzed that these values are a practical compromise. fhey do not proviite a guarantee that in every case firE spread. will- be stopped. ftle aim of the commtttee was to set vaiues that wouLd. greatly improve the hazard.ous cond.itlons now pe1:nitted by nost bullcting bylaws. Goocl. deslgR might
dictite more flie resistance in iome lnstances. flre Cocle require-ment was considered. to be a suitable nininum requirement.
The arrangement of subsection 3.4.5 of the 99d" d,eserves note. Item 1.4.51t ts tfre princi.ple article and' artlcles
3 . 4 . 5 . 2 t o 5 - . 4 . 5 - . 5 d . e a 1 w i t h t h e p r o t e c t l o n o f o p e n i n g s i n conslnrction selaiations. These articles should all be read lf separations are-to be fully understood. flre reaclerfs attentlon ls-drawn especially to the-seconct paragraph of 3.4:2.2. Here ls the exceltlonal- case when a construction s-eparation is per-nittecl wlth-unpiotected. openlngs. The use of unprotected'
op""itrgs-not Liceeaing 20' per 6ent of the wa1l area is allowed oily wilen the wa1l confor.ms to the grade of construction separa-tt;; requfrea and when the wall ls iet back a dlstance that ls half tfr6 atstance requlred for that Srade of space separation.. firerefore, if ; uGiade In separation-is require{r- the wall must have a on6-hour flre reslstai.ce and must be set back from the property line a clistance of 7t feet. With these qualificattons ttri-s selaratlon 1s regard.ed. al equlvalent to a regular constrruc-tion sefuraconstrruc-tion. ftre-advantage dt the cgmprgryi-se is that lt represeirts a for^m of constnrctlon whlch is stil1 very coslmon.
9
' Table 5.7 lndlcates that a cons-bruction separation means a complete banrier betnveen two spaces, including closures and shafti, to protect aLL openlngs. It'must be rrfire-tightrt as the hu1l of a ship is water-tlght. It w111 be observed., when studying lable 7.7 that the requirecl ratlngs for separations, door, and shafts, are not identical. noors are given a lower rating because it was assumed. unlikely that furniture or goods would be piled agalnst a d.oor; hence, hlgher temperature on the unexposed. face of a cloor coulcl be penoitted.
Shafts are requirecL when openings are continuous fron floor to floor one above the other (stair weIl, elevator shaftst air ducts, etc. ) (Ftg. 7). frre fire requirements of shafts are less than those of constmction separations because a fire must flrst break into the shaft and then break out to get to the nerb floor. In essonce, there are two barriers to resi-st the fire ancL therefore, lt nas agreed. that the sum of the flre reslstance of the ba:riers shoultt equal the requj.red 6rad.e of separation
(Fig. 4). llhe openings of a stai.rcase woulcl be as in Diagram_4, FiS. 1. The fi-re reslstance of the fLoor construction would be of llttle value; the stalrcase ls enclosed. withln a shaft as ln Diagram B, tr.ig. 5. Ttre flre resistance of the shaft can be found from Table 3.7 , colunn 4 of the Cod.e. Ihe d.oors leadi-ng to the staircase must provid.e fire reslstance equivalent to that required. 1n column 5 of Table 1.'f . flre separation of the shaft helps to isolate a fire on one floor. Fire-resistive cLosures keep the stair shaft free from smoke, heatr gas, and flamer , thus providing safe egress past a burning section of a buiLdlns and. also safe access for fire-flgbtlng purposes.
Dqcts.- Ia some cases continuous openlngs are mad.e in interior ffi:Eructiqr separations to a1low for the passage of ducts. It ls i.mpractical in many instances for such d.ucts to be enelosecl within a fire-resistlve shaft, Xet if they were allowed to pass
through the separatlon without any protecti-on, then the separa-tlon would be lncomplete. fn order that ar\y separation 1n a bulldlng can perforru efficlently when the bul1dlng is burning there must be-an autonatie fire damper withln the duct at the separatlon; thus lf a flre sfuould burn through a duct lts
spiead frorir one separated cornpartment to another would be hln-d-erecl. Elre-reslstlve closures ancl the types which are allowed a r e inclicated. ln artlcle 5 . 4 . 5 . 5 o f t h e C o d . e .
Spanitrel and Apron Wall-s.- Artlcle 3.4.5.4 requires that openings buildlng with a fire load of 20 pounds per square foot or more and. required separations between floorst be selnrated by an apron or spandrel wa}l not less than J feet inheieht (Fie" 5r. -ftrls ls an example of applying the princlple of preventing-fire spread. When a fire separation between floors is iequirect it ls advisable to conslder actdltional protection at thd edge. Sre flre coulct escape around the edge of the floors
1 0
and lnto the floor above. To overcome thls d.anger the Code requlres a spandrel or apron wall.
Such a preeautlon is not requlred in a bullding havlng a flre load of less than 2O pound.s because the lower lntenslty of a possible flre wurld, ln nost cases, cause thls hazard. to be less slgnlficant.
After studying subsectior- 3.4.5 of the Coite attention should be clirectecl to subsection 3.4.6. It ls irnportant to understancl the basic d.i.fference between these two subseetlons:
S u b s e c t i o n 7.4.5 ls deflnite. I t s h o u l d . b e r e a d 1 n c o n -ffie definltton in Part 1: Admlnlstratlon, and the explanatory notes on separations. All these sections d.eflne separatlons and classify them accordLng t o 6 r a d e s .
Subsection 3.d$ is regulatory and establlshes where separa-ffied between bulldings and what grade they m u s t b e . S u b s e c t l o n s 3 . 4 . 7 t o 3 . 4 . I I a r e s i n i l a r t o 3.4.6. except that they ileal wlth rooms and Srarts of bulldlngs lnstead of the vrhole bu11ding.
It w111 be obsenreci that throughout the requi.rements the grad.e of separatlon required. is dependent on the fire 1oad. Thls can be seen in the d.lrect reference to the flre load i-n s u b s e c t i o n 3.4.6. I n t h e o t h e r s e c t i o n s t h e f i r e l o a d t s n o t mentioned, but the relatj.or:.ship is qulte evident.
(d) Fire Senaration Between Buildln$g I n s u b s e c t l o n 3 . 4 . 6 a
to the fire load i.s required. Fire load,
-TI5:T-Grade 1 Grade 2 Grade 3
lo deternine the constructlon required. to cornply with these fire separation requirements:
(i) the fire Ioad of the occupancy must be heown ( T a b 1 e 3 . I ) i
from the table in l -4-6 the requlrecl Srade of separatlon can be found l and"
The type of constructlon to compl-"y wi.th this 6rasl of separation can be deternined from I a b L e 3 . 7
grade of separation relative a s f o l l o w s : Separatlon (consffii-6r space) I O l b . 2 0 l b . J 0 I b . (i.i ) ( 1 i l )
- 1 1
Ihe followlng exanples c a n b e used: E X A M P L E I / /a-PROPERTY Ltl{E E X A M P L E I T z4''_paopERTy Ltr{E
how the separations B u l l d l n g s A ' a n d B a r e adjacent bulldings. Bul1din6 A ls bullt to the property llne; there-fore a constrtrction
separatlon with no openlngs must be used. Ihe gracle of the con-structlon separatlon ls determi-ned by the fire load of bulldlng A. Slnce a space separa-tion (n) ls belng used. for bulldlng B the walL faclng the property
llne meJr have unlimlted unprotected openings, and the wall finlsh need not be fire reslstlve' provid.ed, hov'lever, that a non-eombustible flnlsh is used tn a non-com-bustlble bulldlng.
ILre space separatlon (n) ls d,etermlned by the grade of separailon re-qulred by the fire load. o f b u i l d l n g B .
Both buildings A and B use space separatlons.
(n and p) are d.etemined by the grade of separa-tion requlred by the fire loads of the res-pective bulldings.
Ihe same regulations
apply to bulldings A and 3 as to building B 1n Example L
Thr.e mlnlmum dlstance
which (n + p) could equal i s 5O feet. I f b o t h A ancl B have lO-Ib fire load,s then each is re-quired. to have an off-s e t o f 1 5 f e e t . lllustrate
3 ,
4 .
l . 2 . 1 . 2 .5 .
3 .
C O N S T R U C T I O N S E P . . " B L D G , A- L 2
Suppose bulldlng A ls an offlce wlth a lO-pound fire load. and buildlng B ls a store wlth a 2O-pouncl fire load" In example I building A would need. a I-hr fire wal-l and n for buildlng B would be 20 feet. In Exanple ff, p and n would be 1 5 a n d 2 0 feet respectively.
Building A requlres openings ln the wall which r1o not exceed 20% of the wall area. Assumlng fire loatls as before, the separatj,on requi-rements are as folLows:
E X A M P L E II I 2 O 7 O U N P R O T E C T E D W I N D O W O P E N I N G S I N C O N S T R U C T I O N S E P A R A T I O N P R O P E R T Y L I N E Building 4
Exterior walls of L hour fire resistance ancl a s l d e y a r d ( p ) o f 7 t 5 n
( * of a Grade 1 space separatlrrn )
BulLdlns B
The ormer of building B el,ects to use a Grade 1 constructlon separation p l u s a G r a d e l s p a c e
separatlon thus achlevlng the requi-red total Grade 2 separation. TLrerefore, the exterior wall has a l-hour flre resistanee a n d i s l o c a t e d l - 5 f e e t from the lot line.
'.c,
(e) geparatioLby RLre Wg-Ils
Another use of sep,aratlons ls a separatlon down the
m l d d l e o f a b u i l d l n g b y a - f l r e w a l l l ( s u b s e C t l o n 4.I.5) ( F l e . 6). Here a new prlnclple nust be introduced". llhls is the prlnciple
that certain kinds of buildings present too great a risk if they are built of unllmlted size. Ilhen a large buildin6 is required, therefore, lt ls often posslble to build 1t only 1f lt is cllvlded by a fire waII givlng the effeet for fire
purposes of trryo separate bulld1ngs with a construction separa-tfon betuveen. A fire wall ls, ln fact, a constnrction separation but the requlrements for fire walls have been developed from expertence, while the constructlon separatlons as defined ln 3 . 4 . 5 a r e t h e r e s u l t o f t h e o r e t i c a l s t u d l e s , h e n c e t h e r e a r e differences ln detall between them.
It is evident that helght ancl area llmitatlons and flre wal1s are 11nked' together- Eel8lrts and areas and types of construction are also linked. The relationship betrrveen these three safety measures ls as follows:
. All buildlngs of constructi-on. ff than that allowedln
( 1 ) ( l i )
L 1
nust be classlfied according to the type the area or height requlred is greater Tab1e 3.6 then two cholces are opens the osrner may dlvlde the bulldlng by fire walls as necesgary to meet the area requlrements; or he may prefer to ehoose another type of construc-tion which pemits greater height or area.
S u b s e c t i o n 4.1.5 deals with the use of fire walls as fire separatlons between buildings or parts of buildingsr Aly part of-a buildlng separated. by a fire wal1 may be consld.ered a separate buildlng, and the area so produced nust meet all reqUtrements of flre exits, separations etc. A fire wall is a party wall for lt ls sharecl by two separate areas of the same buildlng or two d.lfferent buildings. TLre grades of flre walIs whlch must be used ares
Fire load Grade of Separation for Fi-re WalI 1 0 I b . . . . f . . . t . . . G r a d ' e 2 2 0 I b """ " " " " " . . G r a d ' e J 5 0 I b . . . ' . . I t . . . G r a d ' e 4
Ore grad.e of separation ls determlned bJr using the naximum value of the fire loads of either of the adjacent occupancles.
It has been shown how construction and. space separations can be USed.. Reference was mad,e, however, to the fact that fire walls (or party walls) could be used. to separate two builctlngs. flre following exarnple d.eals wlth thls:
E X A M P L E E 1. If Buildlngs A and B have10-lb fire loads than the
flre waIl must be a Grad.e 2 construction separatLont i . e. , 2-hour fire resi-stance. 2. If the fire load of elther
A or B is 20 Ib then the fire walI must have a 5-hour rating o
3. If the fire loail of elther A or B ls 50 Ib then the fire waIl must have a 4-hour rati.ng.
- 1 4
E X A M P L E Y
ff each lncllvidual area A and B were to be bullt wlth lndlvidual constructlon
separatlons at the property l l n e , ( E x a n p l e V), the regu-latlons pertatnlng to cor-struction separatlons woulcl b e v a l i d .
If A and B both had a fire load of 10 Ib then the con-stmction separation for eaeh would be Grade 1 naklng a grade 2 separatlon between the tvvo areas.
If A had a lo-lb fire 10ad and B had a 2O-1b flre load then the total fire separa-tion would be Grade 1.
If A had a 10-1b flre loacl and B had a ,0-1b fire load then the sum of the separa-tlons would be Grade 4. 5. S.E At thls polnt the parallel ends, because lf A had a
20-Ib flre l-oad antl B had a 20-1b flre Load then the con-struotlon separation woulil equal 4 hours fire reslstance. If A had a 2O-1b flre load and B had a lO-Ib fire Load then the const:mctLon separatlons woulcl equal 5 hours flre resistance. If both A and B had ,0-1b flre loads then the construetion
separatlons would equal 6 hours flre resistance. It is eviclent that when indivldual flre separatlons are used to separate
atljoinlng areas the flre protectlon may be lncreased consiclerably. Wtren fj.re walls are used, some special conditions must be met which are not requtred when uslng construction separatlons. In conbustlble builcllngs, when tyvo areas are betng separated by a flre walL, a lnrapet (5 feet ln most cases, 6lnehes betlveen dwelling unlts) must be used so that there wt1l be a complete break ln the roof constrructj.on. A construction separation cloes not require a lnrapet. In both eases fire spread, through roof constrrrotion would be hindered, but with the flre wall this effect would be more posltlveo ,
Also in bulldings of combusttble constructlon a flre waIl must be supported on the found.ati-on and be contlnuous from the fourrdation to the parapet. When the constructlon of the buildlng 1s of non-combustible materlals the fire wall may be supported by the stnrctural frame provi-ded the fire resistance of the stnrotural frame ls as great as, or greater than, that of the fire walL. The flre wall plus frame nust provide a
1 . 2 .
3 .
4 . C O N S T R U C T I O N L . t B L D1 5
contlnuoqs barrler. 0ffsets at floor l-evels are pennit'bed' but the construction of the offset floors and walls must have fire resistance equal to that of the fire rvall (FiS. 7) "
Other requlrements of fire walLs are s-bated in Articles 4 . 1 . J . J a n d 4 . 1 . 5 . 4 o f t h e N a t i o n a l B u i l d l n g C o d ' e .
Fire troad of Occupancy Grad'e of Separation 1 O t o 2 0 l b . . . . G r a d e I
g r e a t e r t h a n 3 0 l b . . . ' . . o . . . G r a d e 2 (f ) tr'ire Separatlon lYith:in BrSlldiJrss
Although it is possible to use fire separations any-where lnside bUildings when, in the opinion of the olvner or archltect, they appear to bil useful, the National Building Code reqrtires fire-separations in certain places as a basic minlmfrfr-FEa-ililarct. fr:6 greatest contrj.bution to internal fire
safety is the separation or isolation of one story fror:a another to cohbat spread. of fire vertlcally, and the provision of safe means of escape by the enclosure and. separatlon of exits.
Fire separatlons are also used to separate major occupanci_es and spe-cial hazard.s as j-ndicated in the following paragraPhst
explal-ned ln the orcl.er in which they appear in the Code.
Maior Occupanci-es.- When there are two or more major occupancies ffing they nust be separated. as stated in
sub-s e c t i o n 1.4,'l and fable 3.8 (Flg. 8). f f o n e o f t h e m a j o r
occupancies requires a Grade 1 separation and the other requS"res a Gride 2 sepaiati.on, the grade of separation must be the
greater of tie two, in this case Grade 2. Ikrus, lf a mercantlle dnd a resiitential 6ccupancy were to be the major oceupancies of a building the grade of- separatlon required according to s U b s e c t l o n 3.4.7 ana fable 5.8 would be a Grad.e 2 separation. Exits. - frie separation of exits from the floo;- eleas of a
5friAi"e G one of the most important life-ffif6dtors
fncorpoiated into any building (subseetion J.4.8). A numerous suppli' of exits is clmmendable; however, if these are fu]l of fliiel, smoke and gases d.uring-a fire they are of no. use to t[e oc6upants of tile buildingl Because of this-' 9a9+ exit must be separited, fron the rest oi tne bulldi:rg so !h?! it is a
contlnuous antl independent vertical member, and its separation must be supporbed tiom the ground so that the collapse of any floor will-not endanger an exit nor the people usJ.ng-lt durlng a flre. ftle separatlon reqqirements of exlts according to s u b s e c t i o s 3 . 4 . 8 a r e :
1 6
The separation ls required only between the ttfloor a r e a s t t o f the building and the exlt (Fig. 9); therefore, if
the exit should be on an exterlor wall facing a street, then
the sldes of the exlt facing the street are not required to be
fire resj-stant (as previously stated, these walls must be
non-combustible 1n non-combustlble constructlon). Fl:re separatlons
are required. for every exit. Number of exits, sLze etc. are
d e t e r m i n e d . 1n Part 3z Use anil Occupancy, Sectlon 5"2O.
Special Occupancy.- Marty special purpose roons, such as
kitchens and furnace rooms, present fire hazards to buj.ldings. Io overcome the hazards which would, arise from the occupancy
of these rooms, speclal regulations have been established.
which are effective regard.less of the use of the building and
of any other fire protection requirements. Tlrese regulations
a r e stated in subsection 5.4.1O of the Code.
Attic, Crawl and DLrct Spaces.- When buildings are separated
all attic, crawl, and duct sPaces
m u s t a l s o be separated (IiS. 10). I f t h i s i s n o t d o n e t h e n
the fire could spread by way of the attic, crawlr or duct space
f r o m o n e e n c l - o s e d . a r e a t o a n o t h e r . S u b s e c t l o n 1.4.11 deals w i t h t h e s e requi-rements (refer directly t o A r t i c l e 1 . 4 . 5 . 1 i n
the case of dricts not enclosecl 1n fire resistlve shafts ) .
5. CONCIUSTON
After consi-dering so many details it is well to remember
the general pri-nciple that regulations are for the purpose of
ensuring a minimum standard. of safety. ILris ls not always too
e a s y to define.
TLre minlmum ls always set by agreement based on expert
opinion on the d.egree of safety whlch the public will tolerate.
From this point onward technl-cal lnfonnatlon, resulting frorn
research or some fo:m of method.lcal investigation, can often
show how the desj-red safety measures can be achleved vrith less
interference or restriction on the actions of those who bui-Id.
Such improved regulations may result 1n building economies,
or a more conslstent standard of safety, or both. Illltichever
is the case it should be welcomed. because efflclency and
safety 6o hand-in-hanil.
ftre new regulations in the National- Building Co<le are
based. on infor:natlon galneil fron research. ALthough not
per-fect they have been acclaimed by many as a considerable
improve-ment over other contemporary regulations. fhe lack of
under-standing which results from their newness is a limiting factor
in their use. It ls hoped that this paper will help to correct
_ 1 7
frre authors of these regulatlons, while defending then are, at the sane t1me, their most severe crltlcs. Developnent of i-nprovod. reguLations did not stop with the printlng of the 1951 edltion of the Natlonal Building Code but has contlnued., and lnprovements w111 be announced from time-to-time. Tod.ay, vtrith new teehnology, much of the old method. of control for
safety no longer applies. Unless bulldlng regulations advance wlth the ti-ures they will be put aslde or sverloohed as a
measure for safety. It is to be hoped. that if building regu-lations are ever less used than they are today it will be because they are less needed and. not because they have become inadequate for thelr task.
References
1 . B i r d , E . l . and S.J. Docking. F l r e in buildings. E d . i t o r s , Ad.an and Charles Black. london 1949, p,liO.
2. Natlonal Fire hevention Assoclation. Hanclbook of fire p r o t e c t l o n . 1 l t h e d l t l o n , 1 9 5 4 , p . 5 1 .
3. Stand.ard methods of fire tests of bulldi-ng construction a n d m a t e r l a l s . A . S . l l , M . D e s i 6 n a t i o n : E 1 1 9 - 5 5 , A . S . T . M . Stand.ard.s Part 4, f955. p.1U7-1187.
4. Bird, E.l. and S.J. Docking. Sire in bulldings. Edltors Adan and Charles Black, lond.on 1949. p.90.
5 . f n 8 b e r g , S.H. ConbustlbLe contents in buildings. U . S .
N a t i o n a l Bureau of Standards, Wash., B.M.S. I49, July J.957. 6. fnvestlgatlons on bulldi.ng flres.
Part III Rediation from Buildlng lon<lon, June 1950. 24p.
National Bulldlng Studies : F i r e s , T e c h . P a p e r N o . 5,
BrblLoStqphll
Ifood, B.l. tr'ire protection through mod.em. building codes. (A correlation of factu.al data and re8ulatory procedure. ) A m e r i c a n I r o n a n d S t e e l I n s t i t u t e , N e v u Y o r k , N . Y . , f 9 5 O . 1 5 6 p .
U.S. Natlonal Bureau of Standards. Fire reslstance classl-f l q a t i o r r oclassl-f buildlng constructions. B . M . S . R e p o r t 92, lYssfufngton, October L9+2.
hesiaLentts Conference on Fire hevention. Report of the comrnittee on building construction, operation and pro-tectlon, Washington May 1947. 1Op.
- 1 8
Brlttsh Stand.ards Insti.tution.
materials and stntctures. Fire tests on buildlngB . S . 4 7 6 t 1 9 5 5 . 2 4 P " Great Britain, Minlstry of Works. Post-War Buil.dlng
Studies No" 20. Flre gradlng of buildtn6s. Part 1: General prinolples and structural precautions by a joint commlttee of the Bulldlng Research Boarii,
D . S . I . R . , a n d . truire Offlcesf Conmlttee. t r o n d o n L 9 4 6 . 1 1 5 P .
2200 0F 2 0 0 0 0 F 1 8 5 0 " F t 7 0 0 0 F t 5 5 0 0 F L o lrl E, = t-E Lrj (L = Lrj F I G U R E I T I M E T E M P E R A T U R E C U R V E
F I G U R E
2
S K E T C H S H O W I N G S P A C E A S A N E Q U I V A L E N T T O A C O N S T R U C T I O N B A R R I E RI lv J , lv lv
-D I A G A D I A G B
F IGURE 3
D I A G R A M S
S H O W H O W SHAFTS ARE REQUTRED
F O R
C O N T I N U O U S
F L O O R T O F L O O R OPEN
I N G S T STAIRCASE
)
F I G U R E 4
S H A F T ACTS AS TWO BARRIERS PERMITTING LOWER
\
I
I
t
I
la,.
3'oo I T-Tl_'
3'o" T-A P R O N I V T-A L L T O S E P A R A T E F L O O R A R E A S ( A T L E A s r 3 ' o " ) F I G U R E 5 S K E T C H E S S H O W I N G H O W A P R O N A N D S P A N D R E L W A L L S P R E V E N T F I R E S P R E A D F R O M F L O O R T O F L O O R F I G U R E 6 S K E T C H O F F I R E W A L L S H O W I N G O N E B U I L D I N G D I V I D E D I N T W O S O T H A T A R E A S O N EACH SIDE W I L L N O T E X C E E D C O D E R E Q U I R E M E N T SW A L L O F F S E T F L O O R S A N D W A L L W I T H F I R E R E S I S T A N C E E Q U A L T O T H A T O F T H E F l R E W A L L F I G U R E 7 S K E T C H O F O F F S E T F L O O R S A N D W A L L F I G U R E 8 C O N S T R U C T I O N S E P A R A T I O N O F T W O M A J O R O C C U P A N C I E S
C O N S T R U C T I O N S E P . O F E X I T ( A C C O R D I N G T O s u B s E c T t o N 3 . 4 . 8 ) C L O S U R E S W I T r r F I R E R E S I S T A N C E A C C O R D I N G T O C O L U M N 3 T A B L E 3 . 7
