When such buildings as the City Flour Mills and the Pantechnicon—types of many other and similar structures in London and the provinces—are burnt out, in spite of their supposed fireproof qualities, it becomes a question of lasting importance as to what is the cause of failure, and whether any so-called fireproof buildings are really so or not. The panic caused in many minds by the newspaper reports of such disasters lasts but a short time, and the true lessons are seldom learnt. With the object, therefore, of endeavouring to place certain facts and suggestions on permanent record, I have collected from many sources various particulars connected with this subject—so intimately connected with the manufacture of fire-proof receptacles.

Much that has been written on fireproof construction is of little value, because the practical bearings of the subject have been lost sight of, and theories of construction are broached that may be good in themselves but cannot be brought into use, because of expense and other inconveniences.

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.

‘I then set it on end in an open yard exactly as it had stood in the warehouse, with the pedestal underneath, the cap above, and the beam across the cap; placed more than a ton of shavings, light wood and heavy wood, round it, and after saturating the whole heap with petroleum applied a light to it. After this I kept men pumping petroleum on it until my stock was exhausted. At the end of 2½ hours I withdrew the post, beam, and other parts from the fire, and within a few minutes from the time they were withdrawn they ceased to burn.

‘I then sawed off, horizontally, a few feet of that part which had suffered most from the flames, and afterwards split the same piece longitudinally with steel wedges, in order to examine its condition.

‘The post was of pitch-pine, about the most inflammable wood I know, and yet after exposure to fire for seven hours, the fury of which could not be exceeded except in blast-furnaces, it contained, and still contains within it, a quantity of uninjured and apparently fresh wood, probably capable at this moment of supporting the whole weight which the original post may have been designed to carry.

‘Immediately after the saw-cut, and again after the cleaving with steel wedges, I carefully examined the centre, and found it just perceptibly warm to the touch, but nothing more, thus proving that the fibre, in which the strength lies, must have been quite uninjured.

‘The lessons to be drawn from this I take to be as follows: A massive storey-post of even the most inflammable wood is absolutely and perfectly proof against any heat that can be applied to it—will not of itself burn at all, but requires a continual supply of highly inflammable substance to keep it burning, and when the supply is withdrawn ceases to burn; and lastly, after being exposed to flames for seven hours of very great intensity, is not injured to a greater depth than about two inches from the original outer surface, and still shows a centre as clean and fresh as when it was first put in.

‘There may be other materials suitable for this purpose which are capable of resisting the effects of heat, and, if so, I hope we may one day hear of them; but, in the meanwhile, I venture to submit what I consider to be strong practical testimony in favour of massive timber for the internal supports of heavily-loaded buildings. Oak or elm is the best wood to use, and will defy destruction for hours.’

Messrs. Dennett, whose name is better known in connection with the Dennett Arch, have introduced a new mode of covering up iron columns in such a manner that they stand through intense heat, and have the advantage of being small in bulk. The accompanying engraving will make the following explanation clear.

Strips of corrugated hoop-iron are fastened at intervals by wire close to the iron column, and all is then encased with concrete 3½ inches in thickness, made as described on page 86. An experiment was tried at Nottingham with one of these columns placed in a fire of wood and shavings saturated with gas-tar, and allowed to burn with a fierce heat for a space of 4½ hours. When half the time had elapsed the column was thrown over, so as to lie horizontally in the fire, and have its whole length exposed to the flames. The fire was at length extinguished by water being thrown on, in order to make the test still more severe, but on examination the concrete casing had not cracked or broken in any part, while the column underneath, as soon as a portion of its covering could be removed, was cool enough to be handled with impunity. It will be interesting to note the development of this invention; for in the event of farther tests in actual practice being as satisfactory as that already named, it is likely to come into very prominent use.

The careless way in which chimneys are built is the cause of frequent danger. By communicating with each other in the same gable, fire will often spread and wrap the whole house in flames. One of the principal streets in Edinburgh had scarcely a chimney-head that was not in this condition. The ends of joists or pieces of timber are sometimes allowed to protrude into chimneys, and then it is generally by accident if the building does not catch fire.

Buildings full of these and other ‘scamping’ work, and so likely to spread fire around, are certainly opposed to the rule that ‘a man may burn himself and his own property, but he shall not unduly risk the lives and property of his neighbours.’

Covering timber—that is, joists or the thin wood of partitions—with sheet-iron is often done, but it is quite useless. When it is known that the Pantechnicon floors were so covered, proof of its uselessness will be at once admitted.

It may be thought that an important fire-resisting substance has been omitted to be mentioned, namely, stone; for in many books, and even in Acts of Parliament, the expression ‘stone, or other fireproof material,’ may be found. But all competent authorities are now agreed that stone of nearly every kind is incapable of resisting the heat of ordinary fires; and when used for supporting weights, or even if hanging unsupported, as in a staircase, frequently is a source of great mischief and probable danger. A flight of stone steps, heated by the conflagration of the house in which it was situated, has been known to collapse immediately upon the admission of cold air through the outer door being suddenly opened.

Stone is therefore inadmissible for fireproof purposes, and should not be used for strong-rooms, or as supports for joists or for any part excepting the floor, where it may crack or crumble without affecting the rest of the building. Granite is, as far as experience goes, capable of resisting immense heat; and it is said the great fire at Boston, U.S., in 1873, was stopped when it came to a huge granite warehouse. But the cost of this material and working it are too great for it ever to be extensively used.

Concrete has been lately brought forward as a good, cheap, and fireproof material for making walls and floors, but if used it should be most carefully made; if broken limestone is used it will not be fireproof; but with a mixture of flints, brickbats, sandstone, pebbles, and cement in suitable proportions, a good wall may be erected. One advantage it has over brick is, that being stronger (if plenty of hoop-iron is used as a bond), it occupies less space, and no plastering, or very little, is needed inside.

There has been no case, as far as I am aware, of a large concrete building being subjected to a severe test; therefore, unless other objects were aimed at, I should prefer a brick building. But some warehouses and mills are so large that brick cannot be used internally in arches; and a subdivision by party walls would destroy the business purpose of the building, and allow of only small compartments in it. Cannot iron girders be used in any way to make them safe? To a certain extent they can, if protected over the entire surface by cement or lumps of fire-clay. There should be but few employed, and allowance must be made for the girders, in case they get heated, to expand without thrusting out the walls. They should be supported on corbels of brick, and be as light as possible consistently with the strength required. If used as means to carry a wall they must be covered as suggested, and with the utmost care, for in this case any twisting or bulging sideways will endanger the wall above.

Whatever system of construction is adopted, there are three things not yet mentioned of high importance to the fireproof quality of the building; namely, the communication between the various floors, the style of window, and the construction of the roof. With regard to the first of these, there is little doubt that the ordinary staircase and the open lift are important aids to the spread of fire; by them the various floors of a warehouse are, when combustion begins, converted into so many furnaces with a connecting flue, and the extension of fire is accelerated by the draught rushing upwards. Though the stairs may be uninflammable and even indestructible, they will be in some measure a source of weakness, unless completely separated from the open rooms, as shown in the designs engraved in the Appendix. For these designs of a thoroughly fire-proof warehouse, I am indebted to Mr. E. Hoole, of Russell Square, London; who has succeeded in planning a building adapted to commercial requirements, and yet possessing the necessary elements of a fireproof structure.

All openings must be fitted with double iron doors if perfect security is required, but with a single door if only ordinary risk is to be guarded against. The construction and fixing of these doors are a most important matter, and should be quite as carefully attended to as if the doorway were to a strong-room. Details of fixing them will be found in the chapter on strong-rooms, and the strength of doors should be the same as there shown. The outer plate of door being a half-inch solid boiler-plate, there must be an air-space behind it, partly occupied by the working parts of the lock, and inside that a casing of non-conducting material. The bolts should be six in number, three in front and three at the back, secured by a lock; and the frame into which they fasten must be solid iron, well built into the wall. The price of such a door, 6 feet high by 2 feet 4 inches wide, is 22l. 10s., and money thus spent would many a time have saved thousands in property.

The Building Act can be complied with by providing a sheet-iron door with a plain barrel-bolt, such a division forming no security whatever, as the iron immediately warps, and allows flame or heat to pass through the opening. In this particular the Act has done much harm, for a false sense of security has been felt when its provisions have been met, and money has been wasted in buying, and labour constantly lost in closing and opening doors that are unable to hinder fire from spreading and ensure safety. Cast-iron hinges are sometimes used for these doors, giving another element of danger. Not long since I saw the ruins of a building which had been divided in its various blocks by such doors. Most of the doors were down in the rubbish, while the openings where they had been high up on the walls had the broken hinges left in the brickwork.

No regulations for fireproof building can be complete without most stringent rules for using the best fire resisting doors, for what the door of a boiler-furnace is to the fire within, the door of a room is to combustion going on inside: it will, if insecure, allow air in to feed the flames so long as there is fuel to burn.

But there are other openings necessary to warehouses; and this leads to the subject of the windows, which are in the fireproof sense a necessary evil. The danger consists in the draught which comes through to feed the fire; but the risk can be lessened by using very thick glass, in small squares, and taking care that no broken panes are allowed to remain in the windows. If anyone takes the trouble to notice such a thing, he will scarcely find a warehouse without some broken squares, which will admit air enough to fan a fire to the temperature of a blast-furnace in a very short time.

Iron sashes should be used; and iron shutters may be also used to cover the windows, capable of being opened easily on the outside by firemen if required. Capt. Shaw states that heavy losses have been caused through the firemen being unable to open iron shutters from the outside, in consequence of their expansion from heat. He also gives a warning against the too common practice in cheap buildings of using glass with bullseyes or dents, through which the rays of the sun become concentrated and set fire, as has been the case, to the interior. Projecting or bow-windows must not be adopted, as fire can more easily pass in this way from one opening to another.

The remaining particular to be noticed is the construction of the roof, by the falling in of which the destruction commenced below it is so often completed. The high Mansard roofs appear to have largely contributed to the destruction of Chicago and other American cities. It is somewhat alarming to see the extent to which they are being employed in England; but whatever form of roof is used, the materials of which the framing is composed should be incombustible, and the ceiling beneath it ought to be perfectly fireproof, so that fire beneath cannot ascend to the roof, or descend from the roof to the rooms. A fireproof ceiling is also valuable for preventing the building being deluged with water from the engines, when fire has attacked the roof only. If any openings to the roof are necessary, they must be constructed with care and placed in a room—not at the top of a staircase, as is so frequently done, where the draught of air is likely to be concentrated.

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.’