42 BULLETIK" 801, U. S. DEPAETMEIs^T OF AGEICULTUEE. 



Slow-buniing construction — sometimes called " mill construc- 

 tion •' — consists of substantial masonry walls and heav}^ timber fram- 

 ing with thick and closely laid floors and roof, all arranged so that no 

 concealed spaces, or pockets, are formed. Although this may be con- 

 sidered a brief definition, there are a number of essential details 

 which should be adhered to if the building is to be worthy of its 

 name. For example, timbers which are carried at the end by walls 

 should be supported there in such manner that failure and falling 

 of the timber would not damage the wall. The value of proper con- 

 struction, in this particular, is shown by the photograph in Plate 

 XXII, figure 1, in which case heavj:^ timbers resting on corbels have 

 fallen without damage to the wall though an entire compartment was 

 consumed. It is true that the first requisite is control of the fire, 

 but a close second consideration is that damage be restricted and re- 

 pair made easy. 



Some general features of slow -burning construction as embodied 

 in a well-designed warehouse are shown in Plate XXII, figure 2. 

 The cast-iron post cap gives a good connection between the post 

 and timbers. 



.DIVISION FIEE WALLS. 



Division fire walls should be of the same material as that specified 

 for such walls of the fire-resistive construction and the general re- 

 quirements are the same. There is, however, one factor to be con- 

 sidered here that is of greater importance than it is in the case of 

 fire-resistive construction — ^that is, stability against overturning or 

 buckling from heat. In the construction having reinforoed con- 

 crete floors and roof, these supply a rigid tie to the- wall; but in 

 slow-burning construction, the wall must stand upon its own merits 

 and must sustain the shock of falling timbers and goods. Sufficient 

 stability usually is supplied by the thickness and other proportions 

 specified previously for brick walls of the bearing type. 



An excellent fire wall is shown in Plate XXIII, The compart- 

 ment was full of cotton, wbich was entirely consumed. Note that 

 the heavy tapering buttresses held this unusually/ long wall against 

 the buckling and overturning which a severe fire frequently causes. ^ 



''The resistance to buckling of the long| wall under the test of heat may 

 be supplied by cross walls or buttresses instead of the additional thickness 

 previously described. Buttresses should be placed at intervals not exceeding 

 100 feet and preferably of 50 feet. TMs type of buttress (shown on PI. XXyi, 

 fig. 3) should be built with and into the wall and not merely against it. The 

 combination of vertical surfaces and off-sets should be such as to be equivalent 

 to a tapering buttress (indicated by the heavy dotted line) having a pro- 

 jection at the first floor of one- tenth the height of the wall ; the face ( or 

 thickness measured parallel to the wall) should be 24 inches. If concrete is 



