A mill at Leeds, at which a fire took place in 1827, was, with the exception of the roof, supposed to be wholly fireproof. The upper floor was filled with flax. The roof fell in, and the heat so affected the iron beams of the floor as to cause them to give way and involve the whole building in destruction.
In concluding the particulars of the general construction of fireproof buildings, I would again urge the use of brick, as the best known material for the purpose of resisting heat; or failing this, iron, protected by plaster, concrete, or brickwork. During the space of a few months there were calamitous fires in some large waterside premises, and at each of them Capt. Shaw states the following results were observed: ‘The bricks were uninjured, the wood was seriously damaged, but only partially consumed; the iron was fractured, and consequently rendered worthless; and the stone was shivered into fragments and totally destroyed.’
CHAPTER VIII.
FIREPROOF BUILDINGS.
II. Patent Systems of Construction, and their Application.
MANY of the suggestions in the preceding chapter have been embodied in the numerous patents brought out by engineers and others for what are termed ‘Fireproofing Systems.’ Among these inventions may be named Messrs. Moreland and Son’s, Messrs. Fox and Barrett’s, Mr. Nasmyth’s, Messrs. Dennett and Co.’s, &c.
Messrs. Fox and Barrett’s patent is one of the oldest, and is still largely used, having been, among other instances, recently applied to portions of the Criterion, in Piccadilly Circus. It consists mainly in substituting iron for wooden joists; and upon the lower flanges of these iron joists are placed pieces of wood, which bear the concrete filling up the space to the floor-boards or tiles above.
The other systems have all, more or less, ordinary concrete as a constituent part, depending largely for its support upon iron or wood beams, and thus probably being, after all, only fireproof to a certain point. One exception must be made in favour of the Dennett system, as in this is introduced a new concrete, treated in a novel and somewhat bold though successful fashion.
This system, known as the ‘Dennett Fireproof Construction,’ is one of great advantage, inasmuch as iron is dispensed with as far as possible, while the space occupied by arched floors is reduced to a minimum. In some cases, indeed, no iron at all is wanted, and yet no room is wasted by heavy piers or supports of brick.
A very superior description of concrete is the body which forms the fireproof medium in this construction. This concrete, unlike that used for foundation and other purposes, is not mixed with any of the ordinary limestone cements, the action of which under fire is well known. A piece of the hardest limestone, when deprived by calcination of its carbonic acid, becomes a body which may be crushed by the least pressure, or if treated with water assumes double its original bulk and falls to powder. Concrete composed of the ordinary lime, inasmuch as it approximates, when set, to the original carbonate, would of course manifest the same characteristics under similar treatment. The concrete which forms the chief element of the Dennett construction has, however, for its cementitious component the sulphate of lime, a body which loses little of its cohesion by calcination. Experiments as to the character of this concrete prove that it remains intact though reduced to a white heat, and that the application of water while in that state does not materially impair its strength or cohesion.