578 PROCEEDINGS OF SECTION J. 



wrought iron girders twist, sag, fail, and drag the floors down (and 

 walls too in some cases), more quickly than timber beams of the 

 same strength. This is the experience of Captain Shaw, of the 

 London Fire Brigade and of many others. 



9. Staircases and lifts cutting through the floors render the 

 foregoing precautions of little service, because they act as vertical 

 flues for fire and smoke. They should therefore be placed outside 

 the main walls, or if they must be kept inside should be enclosed 

 by brick walls, or at least light terra cotta partitions, and shut off" 

 by fire resisting doors. An ordinary wooden staircase may be 

 rendered partially fire resisting by filling in the soflit with 

 concrete. The fire can then only get at one side of the wood and 

 hence it burns slowly. 



10. The roof is of much importance. A fire may be started 

 there by careless plumbers employed on repairs, by sparks from 

 adjoining buildings, or in other ways — while the roof remains 

 intact over a fire there is still a chance of subduing it, when it goes 

 all hope vanishes. If the roof be open, viz. without a ceiling under 

 it, many of the expedients suggested for floors may be a,doiDted to 

 inci'ease its resistance to tire. In some American factories the roof 

 is formed of three inch planks (PI. XXXIX., fig, 4) on beams laid 

 almost flat, and covered with several thicknesses of roofing felt 

 and then a layer of asphalte, finished ofl' with fine gravel i-olled 

 into the asphalte. Asphalte though bituminous, as mixed and laid 

 with grit is fire resisting. With an ordinary roof the best 

 precaution is a thoroughly fireproof ceiling. In Sweden where 

 fires are frequent this is compulsory ; for two story dwellings with 

 attics, a three inch thickness of brick or stone laid in mortar is 

 enforced. One of the floors suggested in the next section might 

 also be introduced in this position with the greatest advantage. A 

 good fire resisting ceiling may, however, be made of timber joists 

 cut feather edged and filled in solid with concrete, or by nailing 

 fillets on the side and then filling in with concrete. The lower 

 edges of the joints only being exposed, they would resist for a long 

 time, and, not being intended to carry any other load, the weight 

 of the concrete is not so objectionable as it would be in ordinary 

 floors. 



11. The size of an undivided building should be restricted. In 

 London the Building Act limits this to 216,000 cubic feet which 

 would allow an area of say 100' 0" x 43' 0" x 50' 0" in height. 

 The greater the subdivision, the greater the security, hence some 

 authorities hold that this is the chief point to attend to, as no 

 floors are absolutely fire proof, but brick walls of suflicient 

 thickness are. In all cases the division walls should rise 

 well above the root. In London and Sydney the minimum is fifteen 

 inches and inMelbourne twelve inches. A greater height might be 

 enforced with advantage in excejjtional cases. Of course no 

 combustible material should penetrate through the division walls. 



