1643 Fire Safety Exposure Hazard

7/28/2019 1643 Fire Safety Exposure Hazard

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I S :1643 - 1988

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I ndian St andardCODE OF PRACTICE FORFIRE SAFETY OF BUILDINGS (GENERAL):

EXPOSURE HAZARD( Fi rst Revi si on )First Reprit OCTOBER 1998

UDC 69981 : 720112

BUREAU OF INDIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DEL HI 110002

September 1988

( Reaffirmed 1998 )


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IS : 1643 - 1988

I ndian StandardCODE OFPRACTICEFOR

FIRESAFETY OFBUILDINGS(GENERAL):EXPOSUREHAZARD( Fi rst Revi si on0, FOREWORD

0.1 This Indiantandard ( First Revision ) was Canada. This revision includes the values inadopted by the Bureau of Indian Standards on K'eSpeCtf loor area ratio, and open space accord-2 May 1988, after the draft finalized by the Fire ing to norms adopted by these countries.Safety Sectional Committee had been approvedby the Civil Engineering Division CkUnCil. o-3 For the purpose of deciding whether aparticular requirement of this standard is0.2 A series of Indian Standards covering the fire complied with, the final value, observed or cal-safety of buildings in general, principles of fire culated, expressing the result of a test or analysis,grading, details of construction, exit requirements shall be rounded off in accordance with IS :2-and exposure hazard, have been formulated. This 1960*. The number of significant places retainedIndian Standard, covering the last aspect, was in the rounded off value should be the same as.first formulated in 1960. In the past 25 years, that of the specified value in this standard.useful data has become available based on studiesconducted in countries such as USA, UK and *Rules for rounding off numerical values ( revised 1.

1. SCOPE1.1 This standard covers requirements regardingspacing of buildings to provide adequate safetyagainst exposure hazard.2. GENERAL2.1 The construction and spacing of buildingswith due regard to their classification ( seeIS : 1641-1988* ) are the major factors to beconsidered which otherwise may lead to a seriousconflagration intensely built-up areas. Thusexposure hazard expressed the danger or risk ofspread of fire through the open air in a buildingon fire to another building situated in the vicinity.2.2 The precautions taken by keeping properspacing of the building prevent spread of fire bydirect contact of flames and hot gases emittedfrom the burning building or by radiated heatand flying brands.2.3 The factors like type of construction ( see1s : 1642-1988t ) based on occupancy distance

*Cede of practice for fire safety of buildings ( general ):General principles of fire grading and classification (f irstrevision .+Code of practice for fire safety of buildings ( general ):Details of construction (first revision 1.

between the buildings and size of the buildinpsinfluence the severity of exposure hazard.3. MAXIMUM HEIGHT3.1 Every building should be restricted in itsheight above the ground level and the number ofstoreys, depending upon its occupancy and thetype of construction. The maximum permissibleheight for any combination of occupancy andtypes of construction should necessarily be relatedto the width of street fronting the building or.floor area ratio ( see 4 ).4. FLOOR AREA RATIO4.1 The comparative floor area ratios for diffe-rent occupancies and types of construction aregiven in Table 1.4.2 Each portion of a building, which is sepa-rated by one or more continuous fire resistingwalls, having a fire resistance of not less than 4 h,extending from the foundation to 1 m above theroof at all points, may be considered to be aseparate building for the calculation of maximumpermissible height and floor area, provided open-ings, if any, in the separating wall, are also,protected by fire assemblies of 4 h.

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1S:1643- 1988TABLE 1 COMPARATIVE FLOOR AREA RATIOS FOROCCUPANCIES FACING ONE PUBLIC STREET OF

AT LEAST 9 m WIDTH

ResidentialEducationalInstitutionalAssemblyBusinessMercantileIndustrialStorage ( see Note 4)Hazardous ( see Note 4 ) 2.8

UL - Unlimited,NP - Not permitted.

( Clause 4,1 )FLOOR AREA RATIOsTYPE OF CONSTRUCTIONr--_--h---_-~

Type1 Type2 Type3 Type4UL 20 14 1-oUL 2-o 14 10UL 15 1.0 08UL 1.0 07 05UL 2.9 23 1.68-O 1=8 1.4 1-o7.5 1.9 16 136.0 l-5 1.3 1-o

1-l 09 NP

NOTE 1 -The FAR/values given in this table aresubject to overall restrictions on the heights of buildingsin the case of educational, institutional, assembly,storage and hazardous occupancies is specified inco1 3 of Table 2.NOTE 2 - This table has been prepared, taking intoaccount the combustible content in the different occu-pancies as well as the fire resistance offered by thetype of construction.NOTE 3 - This table should be modified by theauthority, taking into account the other aspects asgiven below:

a) Density in terms of dwelling units per hectare;b) Traffic considerations;c) Parking spaces:d) Local fire fighting facilities; ande) Water supply, drainage and sanitation require-men ts.

NOTE 4 -The FAR values specified in this tablemay be increased 20 percent for the following services:a)

b)

c). 4

A basement or cellar; space under a buildingconstructed on stilts and used as aand air-conditioning plant room us eaar king spaceto the principal use; as accessoryWatchmans booth, pumphouse, garbage shaft,electric cabin or substation and oth,er utility struc-tures meant for the services of the building underconsideration;Projections and accessory buildings as specificallyexempted under the code; andStaircase room and lift rooms above the topmoststorey; architectural features; and chimneys andelevated tanks of dimensions as permissible underthe code; the area of the lift shaft shall be takenonly on one floor.

NOTE 5 - In so far as single storey storage andhazardous occupancies are concerned, they would befurther governed by volume to plot area ratio ( VPR )to be decided by the authority.

.5. OPEN SPACES5.1 General - Every room intended for humanhabitation should have an interior or exterior

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open space or an open verandah open to suchinterior or exterior open space.5.1.1 The open space inside and around abuilding have essentially to cater for the lightingand ventilation requirements of the rooms abutt-ing such o+en spaces, and in the case of build-

ings abutting on streets in the front, rear or sides,the open spaces provided should be sufficient forthe future widening of such streets.5.2 Open Spaces Separate for Each Buildingof Wing - The open spaces should be separateor distinct for each buildiag and where a build-ing has two or more wings, each wing shouldhave separate or distinct open spaces for thepurposes of lighting and ventilation of thewings.

However, separation between accessory andmain buildings more than 7 m in height shouldnot be less than 1 5 m ; for buildings up to 7 min height, no such separation shall be required.5.3 Residential Buildings

5.3.1 Exteri or Open Space5.3.1.1 Front open spacesa) Every building fronting a street shouldhave a front space, forming an integralpart of the site as below:

Sf. Front Open Space W idt h of St reetNo. Min Fronting the Plotm

i) 1% up to 75+ii) 30 7.5 to 18iii) 45 18 to 30iv) 60 Above 30

NOTE - In case a building abuts two or more streetsthe value of open spaces is to be based on the averagewidth of streets, of 1.8 m for cases (ii), (iii) and (iv).b) For streets less than 75 m in width, thedistance of the building ( building line )should be at least 5 m from the centreline of the street ( see 4.3.5 ).NOTE - This limiting distance has to be determinedby the authority for individual road/street widthstaking into account the traffic flow.5.3.1.2 Rear open space

a) Every residential building should havea rear open space, forming an integralpart of the site, of an average width of3 m and at no place measuring less than18 m, except that in the case of a back-to-back-site, the width of the rear openspace should be 3 m throughout. Subjectto the condition of free ventilation,*For buildings up to a maximum height of 7 m.


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b)

a>

IS : 1643 1988. . I ..^. . . .

TABLE 2 SIDE AND REAR OPEN SPACES FORDIFFERENT HEIGHTS OF BUILDINGS( Clause .3.3.1 )

the open space lett up to halt the widthof the plot should also be taken intoaccount for calculating the average widthof the rear open space. For plots ofdepth less than 9 m, for buildings up to7 m in height, the rear open space maybe reduced to 15 m.Rear open space t o extend t hroughout therear w al l - The rear open space shouldbe co-extensive with the entire face of therear wall. If a building abuts on two ormore streets, such rear open space shouldbe provided throughout the face of therear wall. Such rear wall should be thewall on the opposite side of the face ofthe building abutting on the wider street,unless the authority directs otherwise.5.3.1.3 Side open spaceEvery semi-detached and detached build-ing should have a permanently open airspace, forming an integral part of thesite as below:1) For detached buildings, there shouldbe a minimum side open space of 3 mon both the sides.

NOTE - For detached residential buildings up to7 m in height on plots with a frontage less than 12 m,one of the side open spaces may be reduced to 1.5 m.2) For semi-detached buildings, thereshould be a minimum side open spaceof 3 m on one side.

NOTE -For semi-detached buildings up to 7 m inheight on plots with a frontage less than 9 m, the side.open space may be reduced to 15 m.3) For row-type buildings, no side openis required.

b) In the case of semi-detached buildings, theopen spaces provided on one side shouldbe as in (a) and all habitable roomsshould abut either on this side openspace or front and rear open spaces or aninterior open space.5.3.2 The provisions of 5.3.1.2 and 5.3.1.3 arenot applicable to parking lock-up garages up to3 m in height located at a distance of 75 m inany street line or front boundary of the plot.5.3.3 The open spaces mentioned in 5.3.1.1to 5.3.1.3 should be for residential buildings upto a height of 10 m.

5.3.3.1 For buildings of height above 10 m,the open spaces ( side and rear ) should be asgiven in Table 2.

Sr. No. HEIURT OF &DE AND REAP. OPENBCILDIXW SPACESTOBE LEFT

AROUNDBCILDINQ(1) (2) (3)

m mi) 10 3ii) 15 5iii) 18 6iv) 21 7v) 24 8vi) 27 9

vii) 30 10viii) 35 11ix) 40 12x) 45 13xi) 50 14

xii) 53 and above 16NOTE 1 - For buildings above 24 m in height, there

should be a minimum front open space of 6 m.NOTE 2 -Where rooms do not derive light and venti-lation from the exterior open space, the width of suchexterior open space as given in co1 3 may be reduced by1 m subject to a minimum of 3 m and a maximum of8 m. No further projections shall be permitted.NOTE 3 -If the length or depth of the buildingexceeds 40 m. add to co1 3 ten percent of length ordepth of building minus 4.0 m.

5.3.3.2 For tower-like structures, as an alter-.native to 5.3.3.1, open spaces should be as below:a)

b)

c)

d)

Up to a height of 24 m, with one set-back,the open spaces at the ground level, shouldbe not less than 6 m;For heights between 24 and 375.m withone set-back, the open spaces at the groundlevel should not be less than 9 m;For heights above 375 m with two set-backs, the open spaces at the ground levelshould not be less than 12 m; andThe deficiency in the open spaces shouldbe made good to satisfy 5.3.3.1 throughthe set-backs at the upper levels ; theseset-backs should not be accessible fromindividual rooms/flats at these levels.

5.3.4 The front open space would govern theheight of the building.5.3.5 Int eri or Open Spaces

a) Znner courtyard - In case the whole ofone side of every room excepting bath,WC and store room is not abutting oneither the front, rear or side(s) open spacesit should abut on an inner courtyard whereminimum width should be 3 m.3


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IS : 1643 - 1988Further, the inner courtyard should havean area, throughout its height of not lessthan the square of one-fifth the height ofthe highest wall abutting the courtyard.Provided that when any room ( excludingstaircase bay, bathroom and water-closet )is dependent for its light and ventilationon an inner courtyard, the dimensionshould be such as is required for each wingof the building.Where only water-closet and bathroomare abutting on the interior courtyardthe size of the interior courtyard should bein line with the provision for ventilationshaft as given in 5.3.5 (b).

b) Venti lation shaft - For ventilating spacesfor water-closets and bathrooms, if notopening on to front, side, rear and interioropen spaces, these should open on to theventilation shaft, the size of which shouldnot be less than the values given below:Height of Size of Venti - Minimum SizeBui ld ing lat ion Shaft of Shaft

,rn meup to 10 12 0;

12 2.8 1.218 40 1524 54 1830 80 24

Above 30 90 30NOTE1 -For buildings of height above 30 m, amechanical ventilation system should be installed

besides the provision of minimum ventilation shaft.NOTE 2 - For fully air-conditioned residentialbuildings for lodging purposes,. the ventilation shaftneed not be insisted upon, pronded the air-condition-ing system works in an uninterrupted manner, also,provided there is an alternative sources of powersupply.

c) Out er courtyard - The minimum width ofthe outer courtyard ( as distinguished fromits depth ) should be not less than 24 mIf the width of the outer courtyard is lessthan 24 m, it should be treated as a notchand the provisions of outer courtyardshould not apply. However, if the depthof the outer courtyard is more than thewidth, the provisions of 5.1.2 should applyfor the open spaces to be left between thewings.5.3.6 Joi nt Open A i r Space - Every suchinterior or exterior open air space, unless thelatter is a street, should be maintained for thebenefit of such building exclusively and should beentirely within the owners own premises.5.3.6.1 If such interior or exterior open airspace is intended to be used for the benefit of

more than one building belonging to the sameowner, the width of such open air space shouldbe the one specified for the tallest building asspecified in 5.3.3 abutting on such open airspace.5.3.6.2 If such interior or exterior open airspace is jointly ownedby more than one person,its width should also be as specified in 5.3, pro-vided every such person agrees to allow hisportion of such joint open air space to be usedfor the benefit of every building abutting on suchjoint open air space and provided he sends suchwritten consent to the authority for record. Suchcommon open air space should thenceforth betreated as a permanently open air space requiredfor the purposes of the Code. No boundarywall between such joint open air space shouldbe erected or raised to a height of more than20 m.

5.4 Other Occupancies54.1 Open spaces for other occupancies shouldbe as below:

a) Educational buildings - Except for nurseryschools, the open spaces around the build-ing should be not less than 6 m;b) Insti tutional buildings - The open spaceat front should not be less than 12 m andthe other open spaces around the buildingshould be not less than 6 m;c) Assembly building - The open space at

front should be not less than 1.2 m andother spaces not less than 6 m;NOTE However,. if assembly buildings are,permitt-ed in purely residenttal zones, the open spaces aroundthe building should be not less than 12 m.

d)

e)

Business, merkantile and storage build-in gs - The open spaces around thebuilding should be not less than 45 m.Where these occur in purely residential zone-or in a residential with shops line zone theopen spaces may be relaxed;Industrial buildings - The open spaces.around the building should be not lessthan 45 m for heights up to 16 m, withan increase in the open spaces of 025 mfor every increase of 1 m or fraction there-of in height above 16 m; and

NOTE Special rules for narrow industrial plots inthe city, namely, plots less than 15 m in width, andwith appropriate set-backs from certain streets and,highways, should be applicable.f) Hazardous occupancies - The open spaces.around the building should be as specifiedfor industrial buildings [ see 5.4.1 ( e I I.


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5.5 Exemption to Open Spaces5.5.1 Pro jecti ons i nt o Open Spaces - Everyopen space provided either interior or exteriorshould be kept free from any erection thereonand should be open to the sky, except as below:4b)

cl

4e)

Cornice, roof or weather shade not morethan 075 m wide;Sunshades over windows/ventilators orother openings not more than 075 mwide;Canopy at first level, but not to be used assitout with clearance of 15 m between theplot boundary and the canopy;Projected balcony at higher floors of widthnot more than 09 m; andProjecting rooms/balconies [ see 5.5.1(. d > ]at alternate floors such that rooms of thelower two floors get light and air and theprqjection being not more than the heightof the storey immediately below.

However, these projections into open spacesshould not reduce the minimum required openspaces.5.5.1.1 Accessory bui l di ng - The followingaccessory buildings may be permitted in the open

spaces:4

b)

c)

In an existing building, sanitary block of24 m in height subject to a maximum of4 m in the rear open space at a distance of15 m from the rear boundary may be per-mitted, where facilities are not adequate;Parking lock-up gasages not exceeding 24 min height should be permitted in the sideor rear open spaces at a distance of 75 mfrom any road line or the front boundaryof the plot; andSuction tank and pump room each up to25 m in area.

5.5.2 Proj ecti on int o Str eet5.5.2.1 In existing built-up or congested areas,no projection of any sort whatsoever, exceptsunshades ( see 5.5.2.3 ) extending more than23 cm below a height of 43 m, should projectover the road or over any drain or over anyportion outside the boundaries of the site, pro-vided the projection arising out of the verticalpart of the rain-water spouts projection at the

road level or the water pipe may be permittedin accordance with the drainage plan.

5.5.2.3 Sunshades ov er wi ndows and venti l ktors - Projections of sunshades over windowsor ventilators in existing built-up or congestedareas, when pe


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IS : 1643 - 19884

b)44

The width of the main street on which thebuilding abuts should not be less than12 m and one end of this street shouldjoin another street not less than 12 m inwidth;The road should not end in a dead end;The compulsory open spaces around thebuilding should not be used for parking;andAdequate passageway and clearancesrequired for fire fighting vehicles to- enter

the premises should be provided at themain entrance; the width of such entranceshould be not less than 45 m. If an archor covered gate is constructed, it shouldhave a clear head-room of not less than5 m.6.2 Mired Oceupaacy - When any building isused for more than one type of occupancy, itshould conform to the requirements for the mosthazardous the occupancies. If mixed occupanciesare separated by a separating wall of 4 h firerating, the occupancies should be treatedIndividually.

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Bureau of Indian StandardsRIS is a statutory institution established under the B~rcatc of Irtdiorr Stnttdord.r Act, I986 to promoteharmonious development of the activities of standardization, marking and quality certification of goodsand attending to connected matters in the country.CopyrightBIS has the copyright of all its publications. No part of these publications may lx reproduced in any formwithout the prior permission in writing of BIS. This does nc\t Ijrwlude the lrcc use. in the course ofimplementing the standard, of necessary details, such as symbols and sizes, type or grade designations.Enquiries relating to copyright be addressed to the Director (Publications), BIS.Review of Indian StandardsAmendments are issued to standards as the need arises on the basis of comments. Standards are alsoreviewed periodically; a standard along with amendments is reaflirmed when such review indicates thatno changes are needed; if the review indicates that changes are needed, it is taken up for revision. Usersof Indian Standards should ascertain that they arc in possession of the latest amendments or edition byreferring to the latest issue of BIS Handbook and Standards: Monthly Additions.

Amendments Issued Since PuhlicatinnAmend No. Date of Issue Text Affected

BUREAU OF INDIAN STANDARDSHeadquarters:Manak Bhavan, 9 Bahadur Shah Zafar Marg. New Delhi 110 002 Tclcgr;lms : ManaksansthaTelephones : 323 0 I 3 I, 323 33 75.323 94 02 (Common to all offices)Regional Offices : TclcphoneCentral : Manak Bhavan. 9 Bahadur Shah Zafar Marg 323 76 17

NEW DELHI I IO 002 323 38 41Eastern : 1114 C. 1.T. Scheme VII M. V. 1. P. Road, Mnrlik~ola 337 84 99.337 85 61CALCUlTA 700 054 337 86 26,337 91 20Northern : SC0 335-336. Sector 34-A, CHANDIGARH 160 022 60 38 43

1 60 20 25Southern : C. I. I. Campus, IV Cross Road, CHENNAI 600 I 13

(335 02 16,235 04 42235 15 19.235 23 I5

Western : Manakalnya. E9 MIDC, Marol, Andheri (East) H:J3 92 15. 832 78 58MUMBAI 400 093

{X327891,8327892

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1643 Fire Safety Exposure Hazard