22 BUIxLETIN 801^ U. S. DEPAKTMEXT OF AGEICULTTJEE. 



EXTERIOR WALLS, 



Tlie exterior wall of tlie fire-resistive warehouse sliould be of 

 noncombiistible material. It need not, hoTvever, be of such material 

 and- design as to offer as long-sustained resistance to fire as the di- 

 vision wall unless that particular exterior wall has a very hazardous 

 exterior exposure, in which case it should conform to requirements 

 for a division fire wall. The material suitable for the usual ex- 

 terior wall is not as limited as is the case for the division fire wall. 

 Brick, concrete (with or without steel reinforcement), stone, and 

 sand-lime brick are all acceptable, and usually are to be given pref- 

 erence in the order named. "V^^iere there is no exposure hazard, 

 hollow cement blocks and hollow clay wall tile may be used for panel 

 walls of two-story buildings, but even in this case the adoption of 

 this material for a fire-resistive warehouse is not desirable.^ 



In discussing exterior walls, brickwork is the basis for stating 

 thickness, just as it is for the division fire wall, but in this case no 

 increased thickness is required when plain concrete is substituted 

 for brickwork. (In this connection it is well to note the require- 

 ments for " panel walls " set forth later.) 



The exterior wall of the usual bearing type which supports floors 

 and roof may be 4 inches less in thickness than was specified for a 

 division fire wall, provided the minimum thickness be 12 inches for 

 the first story, where the height of the story does not exceed 18 feet, 

 and that where there is more than one story the wait for the top 



^ Brick, cement blocks, and stone may be laid in lime mortar, except that for 

 tlie portion of the wall below and 2 feet above the ground level, the cement 

 mortar, previously mentioned, should be used. The lime mortar should con- 

 tain one part lime putty, or hydrated lime, to not more than four parts sand, 

 the exact proportion being adapted to the character of the sand used. (See 

 U. S, Bureau of Standards Circ. 30; Lime: Its Properties and Uses, 19'11.) 

 The replacement of one-fourth of the lime with a like amount of Portland 

 cement will give excellent results without a great increase in cost. In this 

 case the mortar may be mixed in advance and the cement added as the mortar 

 is used. Tliese mortars are equally suitable for the cement blocks. 



Walls of brick — either clay, clay and shale, or sand-lime — and of concrete 

 with and without reinforcement may be used to support the roof and floor, 

 this construction being a "bearing wall." In case of walls of cement blocks 

 or clay tile it is best that the floor and roof slab be supported independently 

 by columns and beams and that the wall be built independently so as to be 

 tied to the floors and columns in such manner that the wall will support only 

 its own weight, thus forming a " curtain wall." In case the building is a 

 number of stories in height and the tile or blocks are used it will be better 

 and more economical to use a "panel wall" built between the columns and 

 beams in such manner that the inclosing wall for any floor is supported by 

 that floor and not bj^ the wall for the story below. 



