I remember, for instance, some gentleman recommended that every room of a building should have floor, walls, and roof lined with galvanised tanks of water, connected by an elaborate system of pipes and so on—not at all a bad idea, but utterly impracticable for business purposes. Another suggestion was that there must be no windows in a building, as through them a draught passes to increase fire.
But in these instances, as in many others, the main fact is forgotten, viz., that what is wanted is the best possible mode of making a fireproof structure that is also adapted for ordinary business purposes. This is what I take to be the point. Cases where exceptional security from fire is needed seldom occur and are more easily met. Dealing, therefore, with an ordinary warehouse, which is to be a fireproof building, it should be remembered that its fire-resisting qualities are determined not only by the materials of the actual structure, but also by its interior fittings, and, above all, by the goods stored or manufacture carried on in the place. A house of brick only obviously will not burn, but fill it with cloth or cotton goods, and the house as well as the goods may be destroyed. No hard-and-fast line can, therefore, be laid down, for every case may be different. I will endeavour to notice the risks of buildings commonly erected and the remedies for each—a combination of which remedies will make a good fire-resisting structure. Among the numerous books and papers on fires to which I have been able to refer I have found no information so clear, precise, and practical as that to be had from the late Mr. Braidwood’s[3] paper, read before the Society of Arts in 1856, and the excellent book entitled ‘Fire Surveys,’ by Captain Shaw, the present Chief of the Metropolitan Fire Brigade. Mr. Braidwood laid down certain rules, which have never been improved upon; while both he and Capt. Shaw express views so alike, and with the confidence of men who have gained their experience from actual results, that it seems better to be guided by them than by all other writers put together. Not that I would disparage these latter, for it is well known that there are architects and others who have contributed much to the solution of the mystery which was so long attached to fireproof building. Mr. Braidwood gives a comparison to demonstrate that what would be safe construction for one building would not be for another. He says: ‘Supposing an average-sized dwelling-house, 20×40×50=40,000 cubic feet, built with brick partitions, stone or slate stairs, wrought-iron joists filled in with concrete, and the whole well plastered. Such a house will be practically fireproof, because there is no probability that the flooring in any one room would make fire enough to communicate to another. But suppose a warehouse equal to twenty such houses, with floors completely open, supported by cast-iron pillars, and each floor communicating with the others by open staircases and wells; suppose farther that it is half-filled with combustible goods, and perhaps the walls and ceilings lined with wood. Now, if a fire takes place below, the moment it bursts through the upper windows or skylights the whole place becomes an immense blast-furnace; the iron is melted, and in a comparatively short time the building is in ruins; and, it may be, the half of the neighbourhood destroyed.’
Such a warehouse, as here described, is the type of many now in existence, and yet people wonder how they can burn. The wonder is rather why so few are burnt; and one explanation is, that the majority are scarcely used when gas and lamps are required, the hours when the workpeople and clerks are about having been so much restricted that for at least a great part of the year the work does not extend beyond daylight. When a fire has once got hold of a warehouse, unless it is built in compartments, the firemen can do nothing but prevent its spreading to adjoining erections; and, as this cannot always be done successfully, a badly-built warehouse is likely to bring disaster upon its neighbours.
But a building may be built to give security; and Mr. Braidwood’s opinion was ‘that the real fireproof construction for such buildings is brick arches, supported on brick pillars only.’ This mode of building, however, involves so much expense, and occupies so much space, that it cannot be used with advantage. The next best plan is to build warehouses in compartments of moderate size, divided by party walls and double wrought-iron doors, so that if one of these compartments takes fire there may be a reasonable prospect of confining the fire to that compartment only.
Cast-iron is largely used in building because of its cheapness; but it is exceedingly dangerous, for it gives way from so many different causes that it is impossible to calculate when it will give way. The castings may have flaws in them, or they may be too weak for the weight they may have to support, being sometimes within ten per cent. or less of the breaking weight. The expansion of girders may thrust out the side-walls. For instance, in a warehouse 120 ft. × 75 × 80 ft. there are three contiguous rows of girders on each floor, with butt-joints; the expansion in this case may be 12 inches. The tie-rods to take the strain of the flat arches must expand and become useless, and the whole of the lateral strain be thrown on the girders and side-walls, perhaps weak enough already. Again, throwing cold water on the heated iron may cause an immediate fracture. For these and similar reasons the firemen are not permitted to go into warehouses supported by iron when once fairly on fire. The effect of fire on cast-iron, as stated by the late Sir William Fairbairn, F.R.S., of Manchester (Seventh Report of the British Association, vol. vi. p. 409), is, that the loss of strength in cold-blast cast-iron, in a variation of temperature from 26° to 190° = 164° Fahr., is 10 per cent., and in hot-blast at the variation of from 21° to 169° Fahr. is 15 per cent. Now, if the loss of strength advances in anything like this ratio the iron will be totally useless as a support long before the fusing-point is attained. Respecting the strength of cast-iron columns here alluded to, I may state that Capt. Shaw says: ‘At a temperature of 212° Fahr., or the boiling-point of water, cast-iron loses 15 per cent. of its strength. At the temperature of molten lead, 612° Fahr., it has probably no strength at all; and at the temperature 2,787° Fahr., which is probably much below that of the centre of a large building, it becomes liquid.’ A very clear proof of the inability of cast-iron to resist the effects of fire was given at the destruction of a chapel in the Liverpool Road, Islington, on Oct. 2, 1848. The chapel was 70 feet in length and 52 feet in breadth, and was completely burned down by a fire which commenced in a cellar. After the fire it was ascertained that of thirteen cast-iron pillars, used to support the galleries, only two remained perfect; the greater part of the others were broken into small pieces, the metal appearing to have lost all power of cohesion, and some parts were melted. It should be observed that these pillars were of ample strength to support the galleries when filled by the congregation, but when the fire reached a certain point the pillars crumbled under the weight of the timber only, lightened as it must have been by the progress of the fire. In spite of such a case as this, which is but an example of what has often happened to other buildings, cast-iron continues to be used not only for ordinary purposes but actually for so-called fireproof buildings. It may safely be asserted that no place in which there are unprotected iron-supports can possibly be fireproof; and if this test is applied to many erections thought to be secure, it will soon be seen how few there are that can be relied upon to withstand excessive heat.
The reckless mode of running up houses, as speculative builders appear to delight in doing, and supporting the front on light columns, is a most dangerous proceeding. Capt. Shaw has cited a case of a corner building lately put up, 90 ft. long and 70 to 80 ft. high, supported entirely on iron columns, without any wall, wood, or brickwork. There is no doubt that at the ordinary fire temperature of 600° to 700° Fahr. the whole building must inevitably fall down, and such a heat could easily be created by the combustion of a very small quantity of household furniture. The fashion of having all the available space for large shop-fronts gives rise to this dangerous work. Most of the elaborate shops and offices lately built in London depend entirely upon iron supports; and some day, when a fearful accident is the result, the public will appreciate the danger.
In the early part of this year large corner premises were built not far from the Elephant and Castle, in the South of London, and I watched their erection with some interest. The house of four storeys was run up (a better term than built) in a month. The corner angle is supported by two thin iron columns, and between these and the other ends of the building are two wooden posts, but the weight chiefly rests upon the iron columns, which are most certainly unable to sustain the tons of brickwork above it in case of severe fire. As long as architects and builders and their employers give up security for the sake of economy and space, this sort of work will continue to be put up, unless interfered with by a new Building Act.
What ought, then, to be used for supports? If the brick columns are inadmissible, then, strange to say, wood posts are the best, or an iron support, well protected by brickwork, cement, or plaster. The fact is, though iron is incombustible, it is itself not fireproof; and, on the other hand, though wood is combustible, it may be used in such a manner as to resist fire for a great length of time. Capt. Shaw’s recent experiments with a wooden post had such an extraordinary result that, with his permission, I append the particulars, from a letter of his inserted in ‘The Times’:—
‘A few months since a fire occurred in one of the enormous warehouses for which the docks in this metropolis are remarkable, and raged with great fury from a little before six in the morning till about eleven in the forenoon, when it was extinguished, and a very large proportion of the building and its contents saved. The warehouse was constructed of brick walls; it had wooden floors, supported on wooden beams, which, in their turn, were carried on wooden storey-posts about twelve inches thick; and although serious damage was done, not one portion of the heavy woodwork was destroyed. After the fire I was allowed to remove one of the storey-posts, with a section of the beams, and other parts surrounding it above and below. This post had been subjected to the full action of the fire during the whole of its duration, as already mentioned; or, making full allowance for everything, including the delay of the fire attacking the particular spot on which it stood, and the time at which the cooling process commenced, certainly not less than 4½ hours.
‘As we had used large quantities of water, and it was probable that the wood might have been somewhat saturated, I had it carefully dried for several days before a strong fire until not a trace of moisture remained in it.