03.STRUCTURAL SAFETY



STRUCTURAL SAFETY  

54. Structural standards:-

1) All structures shall be so designed, built and maintained that under the conditions of dead and live loading, the stresses in any of the materials of construction or in the material on which a structure rests shall not exceed the permissible limits as laid down in the National Building Code published from time to time.  

(2) When an existing building or other structure is enlarged or otherwise altered, and portions thereof affected by such enlargements or alterations shall be strengthened where necessary, so that all loads will be supported safely without exceeding the permissible stresses prescribed for the materials of construction and for the structural members in the National Building Code published from time to time.  

(3) No building the external walls of which are timber framed construction shall be erected, re-erected or altered materially so as to consist of more than a ground floor and one upper storey; provided that the Planning Authority/Local Authority may by special order grant permission for the erection of such a building of two storeys or for the construction of one or more additional storeys if satisfied that such buildings will be, or are of thoroughly sound material and construction and can safely support the same.  

55. Live loads and wind loads in buildings-

Live loads and wind loads shall conform to those specified in the National Building Code published from time to time.  

56. Foundations --

 1) The foundations of every building shall be so designed and constructed as to sustain the dead load of the building and the super imposed load and to transmit the loads to and distribute them over the soil in such a manner that pressure brought to bear on the soil by these loads shall not exceed the safe bearing capacity of the soil.  The safe bearing capacity of the commonly occurring rocks and soils are given in Schedule I.  

(2) In the design of basement walls and similar approximately vertical structures below ground level, provision shall be made for the lateral pressure of the adjacent soil and the walls shall be designed as retaining walls.  Due allowance shall be made for possible surcharge due to fixed or moving loads.  When a portion or the whole of the adjacent soil is below a free water surface, computations shall be based on weight of the soil diminished by buoyancy plus hydrostatic pressure. 

(3) In the design of basement floors and similar approximately horizontal constructions below ground level, the upward pressure of water, if any, shall be taken as the full hydrostatic pressure applied over the entire area.  The hydrostatic head shall be measured from the underside of the construction.  

57. Walls-

Every person who undertakes construction of a residential or commercial building shall construct every external wall, every wall abutting on an interior open space and every party wall included in such work in accordance with the minimum thickness excluding plaster given in Schedule II.  The thickness shall apply to masonry walls built of bricks or concrete blocks and whether built in the lime mortar (1:2) or cement mortar (1:6) or composite mortar (1:2:9). In no case the intensity of load on the masonry should exceed the safe permissible stress of the construction as laid down in the National Building Code published from time to time.  

(1) Every person who undertakes construction work on a masonry wall of public or industrial buildings shall construct every external wall and every party wall included in such work in accordance with the thickness excluding plaster as specified given in Schedule III and in every case the thickness shall apply only to walls of brick masonry built in lime mortar (1:2) or cement mortar (1:6) or composite mortar (1:2:9).

(2) In every case the thicknesses of the wall in any story height shall not be less than 1/14 of that storey height.  

(3) For the purpose of clauses(1) and (2) any loft balcony or mezzanine floor of more than 3 m. (10 ft.) which shall be considered as forming a storey for determining the thickness of the walls which support it.  

(4) Every person who shall undertake construction work on masonry walled buildings shall construct in accordance with the following conditions, every cross wall included in such work which in pursuance of the bye-laws on that behalf may as a return will be deemed a means of determining the length of any external wall or party wall of such buildings and in every case the thickness prescribed shall be the minimum thickness if which any such cross wall may be constructed; and the several specifications shall apply only to wall built of brick masonry;   

(a) the thickness of every wall excluding plaster shall not be less than 12 cm, or 4 1/2” in case of brick masonry in cement mortar and reinforced at every fourth course and not less than 23.5 cm. Or 9” if cement or lime mortar is not used.  

(b) when bricks or superior quality (wire cut, brick) are used with richer mix cement mortar, suitable, reductions in thickness of wall may be allowed provided the stress developed at any point of the wall does not exceed the permissible limit as laid in the National Building Code published from time to time.  

(5) In case masonry work is done with mud mortar the following restrictions shall apply:-  (a) the height shall not be more than 7.6 m. Or;  

(b) the thickness shall be 12 cm more than that prescribed under clause (1) and (2) ; and  

(c) the pressure at base or any other point shall not exceed 22 tons per sq.m.  

(6) In case of building designed by qualified registered Architects, Engineers or Licensed Supervisors who are considered by the Planning Authority/Local Authority sufficiently qualified to work out structural strength, the thickness prescribed in this bye-law may be deviated from, provided the proposal is supported by calculations and a certificate is recorded by the Engineer, Architect or Licensed Supervisor in the following form:  

Certified that the structural parts of the entire building have been designed on the basis of calculations and are considered safe in accordance with the permissible stresses and the slenderness as laid down in the National Building Code published from time to time.  

Note: Even in such cases provisions made under the Act may be kept in mind by the Planning Authority/Local Authority while sanctioning the plan.  

58. Damp-proofing of walls-

(1) Every wall and pier of the building except when built on materials such as steel or plain reinforced cement concrete 1:2:4 shall be provided with a dampproof course of either of the following:-  

(a) one part cement, two parts coarse sand and five per cent pudlo or some similar water proofing materials;

(b) bitumen sheetings;

(c) a layer of 1:2:4 cement concrete 4 cm. Of 1 1/2” with two coats of bitumen on top or with pudlo;

(d) Impervious stone slabs or 1:3:6 cement concrete; slab of not less than 10 cm. thick and not less than the width of basement fixed in cement mortar 1 : 3 ; and

(e) any other impervious material approved by the Planning Authority/Local Authority. 

(2) Such damp-proof course shall be laid at a level not higher than the lowest part or underside of the construction of the ground floor and shall extend to the full width and extent of such walls or piers.  It shall be at least 2 cm. (Or 3/4”) thick.  Where the dam-proofs course is provided below the plinth level vertical damp-proof course shall be provided between the floor and the inside of the plinth.  

59. Insulation against heat and cold :

Standards of Thermal Insulations:--(1) All buildings and such structures for the proper insulation of heat and cold may be required by the Planning Authority/Local Authority to comply with the standards of thermal insulation prescribed in National Building Code published from time to time.  

(2) All roofs of habitable rooms wherever necessary and structures shall be provided with thermal insulation by any one of the following methods :  

(a) by the addition of layer of some insulating material between the roof and lime     concrete terracing ;  

(b) by the formation of the air spaces ;

(c) by the use of materials of low conductivity instead of brick-work or concrete ;  

(d) as directed by the Planning Authority/Local Authority.  

60. (a) Sound Insulation :

All buildings and structures for the purposes of insulation against sound may be required by the Planning Authority/Local Authority to comply with the standards of sound insulation specified in the National Building Code published from time to time.    

(b) Fire safety : For requirements pertaining to the fire safety and fire resistance of buildings, the provisions prescribed under the National Building Code issued from time to time shall be followed.  

(c) Lightning :For lightning  protections of buildings under different uses the provisions as prescribed under the National Building Code issued from time to time shall be followed. 

(d) Electricity : The specifications and requirements for electrical installations in all buildings under various uses shall be as prescribed by the National Building Code issued from time to time or as prescribed by the State Electricity Department..

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