20 BULLETIN 801^ L^, g, DEPAETMENT OF AGEICULTUEE. 



in height, from floor surface to floor surface) or each increment of 

 30 feet, the wall should be increased in thickness 4 inches.^ 



The foregoing thicknesses apply to a wall not more than 100 feet 

 long. If this length is exceeded the thickness of the wall should 

 be increased 4 inches throughout for each additional 100 feet or part 

 thereof, except that for reinforced concrete the increased thickness 

 may be on*e-half that stated above.^ 



Wliile it is not intended to discuss here the matters pertaining to 

 all details of a building code, it may be well to point out some 

 dangers of poor construction in the division fire wall. Openings in 

 division fire wall should be avoided as far as x^ossible. It seldom is 

 necessary to provide any openings in such a wail of a warehouse 



"^ For the final 4 inches of thickness in excess of 16 inches pilasters may be 

 substituted provided such pilasters are built with the wall, are opposite each 

 other on both sides of the wall, and are located and proportioned suitably. 

 Such pilasters should have a projection from the wall of 4 inches on each 

 side, and the face (or dimension parallel to the wall) should be a minimum 

 of 16 inches and not less than one-eighth of the spacing of the pilasters 

 measured between centers. The spacing of pilasters should not exceed 25 

 feet. The location shbukl be such that no part of the wall will be loaded 

 beyond the allowable unit working stress of the material used. 



^ While stated thicknesses for -walls seem arbitrary, the explanations made 

 show that a division wall is subjected to more severe tests during a fire as 

 the height or length of the wall increases. Difference in thickness of brick- 

 work necessarily must be made in units of 4 inches, and so heights and lengths 

 of walls stated are adjusted to this variation. Good practice has shown that 

 the above thicknesses are very satisfactory for a wall serving as a barrier 

 against fairly intense and continued heat. A wall of less thickness may affor(? 

 good protection, but it should be borne in mind that a division fire wall should 

 represent^ " the last line of defense " in a fire ; and if the values behind the 

 Vail jtistify the expense of a -wall, then one which vsall afford dependable pro- 

 tection is the best investment. 



An exception to some of the foregoing requirements for a division fire wall 

 is found in panel-wall construction esiiecially adapted to reinforced concrete 

 roof and floors. The panels may be built of brick between supporting colunms 

 and floor and roof slabs or beams, after these have been constructed, or the 

 rianels may be of reinforced concrete cast with the floors. In such a case the 

 stability of the wall and its action in resisting expansion is cared for by the 

 concrete framework, and each panel of brickwork may be treated as a sepa- 

 rate and independent division wall in applying the preceding requirements. 

 These requirements for thickness, however, may be modifled to the extent of 

 permitting a brick panel wall to be only 12 inches in thickness, or a reinforced 

 concrete panel 10 inches in thickness, for a height of 20 feet for panels not ex- 

 ceeding 30 feet in length. The mortar used for laying brick walls of this 

 character should be the cement-lime mortar described, as it is more com- 

 pressive, and so in this confined position may withstand the severe compressaon, 

 from expansion. This form of construction usually will not be economical as 

 compared with the regular division wall cari'ying the floors and roof, except 

 in case the building is more than four stories high or the wall is excessively 

 long or there are such special conditions as are discussed under the heading of 

 roof and floor construction. 



