Page:The Building News and Engineering Journal, Volume 22, 1872.djvu/268

 250 THE BUILDING NEWS. Maron 29, 1872. three-quarters of a cubic yard, and, standing low, is easily filled. A railway tunnel is subdivided into the driftuay or heading first excavated to get the true line of the tunnel and to draw off the water ; the shafts through which the exca- vated material is drawn to the surface, and the loose ends, being the length at each end of the tunnel from daylight towards the first shaft. a HOW TO BUILD SCIENTIFICALLY WITH THE AID OF MODERN IN- VENTIONS.—X. FLOORS. TRE-PROOF.—What changes have not come oyer the meaning of fire-proof ! Among my early experiences no building was considered fire-proof that had not iron joists and brick arches. Any one who ventured to differ with the opinion of that day was simply considered one of the old school ; ‘‘ an obstruc- tive,” “ pig-headed,” and other elegant terms were applied to him. Do not think that I consider the times in this respect are much improved, for I think that there still exists this contempt for those who reason and will not adopt new theories, simply because they are new and have obtained a majority in their fayour. But scarcely can I find a case which better illustrates the errors that are forced upon us, than this subject of fire-proof. I will not weary my readers, as I might easily do, with quantities of quotations from high authorities for some years past eulogistic thereof. It will be more in accordance with my object to say, that now it is generally ad- mitted that no floor can be called or con- sidered fire-proof that has iron used in its construction—such is the present position of iron. Hereafter we shall have to note some of the remedies or casings proposed to be used to render more secure, or more properly, to protect iron from contact with the flames. I think it was Captain Shaw, the chief of the Fire Brigade, who first ealled attention to the danger of the use of iron, which he did at a meeting of our Institute, and I remember I was, with many others, surprised at hearing him give his ex- perience of how much more difficult and dangerous it was for his men to extinguish fires in so-called fire-proof buildings than in ordinary buildings, where wood not merely was used in floors and roofs butalso in stairs. By reference to the ‘ Transactions,” I find this was as long ago as 1869. The conclusion, then, to be drawn from the latest experiences is, that there is only one kind of fire-proof flooring, and that, as Professor Lewis says—‘ In fact, the re- sult really seems to be that the only secure protection from fire isa structure of brick arches on brick supports. Nothing else that I can call to mind will stand the effects of great heat and the actions of the flames. . . I cannot repeat too strongly that, with a large mass of fire, no construction, under any circumstances, could be considered as really fire-proof, except solid arches on brick supports.” Of course, from the distance between the walls, it would, in all ordinary buildings, be impossible to expect such con- struction to be adopted, necessitating so great a loss of space between the floors. Weare compelled further to decide that the term as used in the present Metropolitan Building Act is wrong. I therefore pro- ceed to consider the new term of Fire ReststmG FiLoors.—Under this head I propose to treat of the various kinds more generally used, and their comparative merits. Dennett’s.—This is a modification of the conerete avch. For its construction iron girders are placed from seven to ten feet apart, and the arch springs from the flanges with a rise of about one inch per foot of span. The material used is sulphate of lime, which is obtained from quarries in the midland counties. This forms the cementitious body, while the other components may be broken brick, stone, burnt clay, or ballast. In com- mon with all arches, it must surely exert a certain. (if small) thrust on the walls (though I think this is stated not to be the fact), and it should not be exposed to the action of water or frost. The cost for ordinary floors for rooms for model houses complete is {4 4s, to £5 5s. per square of 100ft., including rolled iron joists ; for floors of larger dimen- sions, £5 5s. to £6 10s. per square. Phillips’ (Homan’s Patent).—This system of flat flooring was introduced in 1866. Its peculiarity is, that in lieu of gypsum, or sulphate of lime, Portland cement is the cementing ingredient, its strength, when in compression, being equal to a London stock brick. But as it is comparatively weak in its tensile resistance, light bars of T iron are placed about 6in. to 12in. apart on the lower flanges of the iron joists, and centreing boards applied below, which must remain until the concrete is set. The concrete is then spread between the joists to the depth of 4in. or 6in. embedding the 7 bars and the lower flanges of the joists. These T bars are provided in proper lengths, so as to satisfy the require- ment of easy execution. A key for the counter ceiling is afforded by the rough con- crete, so that no laths are required. The cost for one square of 15.0 span, including joists and cement, is £6 4s. . French System.—This is a system of floor- ing frequently employed, in which rolled iron joists are placed about 35ft. apart, and a grating formed of 3in. square iron bars bent over the flanges of the joists, and suspended between them. Perforated bricks or tiles are then placed on the grating so formed, and plaster is run in between them, filling up the interstices, and forming a solid floor, It is a costly construction, and the cost in the neighbourhood of London for one square of 15.0 span, including iron joists, bricks, and plaster, is £11 9s. Advantages.—Does not add fuel to the fire. No dry rot. No harbour for vermin. No inflammable gas. Does not add materials to aid the fire. Foremost, certainly, among the advantages this must be placed. The second and third advantage are so ap- parent that I need not dwell on them. No inflammable gas. Here, I doubt not, my reader will require some explanation. I cannot better give it than by quoting Captain Shaw, who says: ‘ That if there were applied a certain amount of heat to wood of any kind, more especially soft woods, a highly inflam- mable gas was generated, and that gas ascend- ing to the upper parts of the building on fire in a heated condition, was readily ignited there.” Top floors have been burnt out from this cause, while intermediate floors have re- mained uninjured. Norr.—It should be remembered that hollow bricks used in any fire-proof or resist- ing building are, according to Captain Shaw, objectionable, for the reason that the confined air, expanding with the heat, splits the bricks. Disadvantages.—The cost. Little addi- tional security compared with wood floors, when the latter are well pugged. Treacherous- ness in hour of trial. Difficulty and danger to fireman. The cost.—This is undoubtedly a great drawback. ‘The cheapest fire-resisting floor does exceed the cost of ordinary flooring by about one-third. We have already made comparisons of the various kinds of fire- resisting floors in more general use. Little additional security.—I would confirm this statement by quoting Captain Shaw: ‘“Numerous instances oceurred in which lath and plaster lad been the means of saving large portions of a building from fire, where stone and iron failed whenin close contiguity with the fire. With reference to Mr. Fairbairn’s experiments on the application of iron in buildings, the plan was recommended of having iron girders for floors, supported by iron columns. Now, any one who visited the fires in London would find instances proving that that was not a good mode of construction ; and there were many cases within his own knowledge in which it had failed. . . That iron was unsafe in connection with buildingsin case of fire could scarcely be denied. . It was curious to witness the extraordinary shapes which the iron took, showing that even in the early stages of a fire iron was very considerably affected, crack- ling and warping in every possible direction.” Professor Lewis on this point says, ‘¢ I would trust strong wooden timbers, thickly pugged and supported on strong wooden posts, in preference to iron girders on iron columns.” Mr. Groves [would quote also in confirmation: ‘« With the use of iron which proved so in- jurious in the conflagration in Tooley-street, and I believe has failed in many other large fires, especially the horizontal portions (beams, &e.), and even the vertical (pillars, &e.), have been known to fail.” I have, I trust, made sufficient quotations, without adding more, to show how small is the additional protection from the use of fire-re- sisting material. The remedy proposed is the casing or covering up the iron so that it shall be protected from the action of the fire. Here again, I think wood will be also, if not quite, as secure; a wood floor, well pugged with a good lath and plaster ceiling, will nearly equal the security that is really afforded by so- called fire-proof and fire-resisting materials. It is certainly curious that such a wood floor was recommended as protection from fire (by the first architects of that day), almost a century ago, and that in their endeavour to obtain fire-proof floors they experimented on several methods of preserving wood from fire, and decided that none fully effected that object. Treacherous.—No one who has been over a building aftera fire will want to be told more fully as to the danger and uncertainty. The fireman walks fearlessly where wood is the material ; but let it be iron and the utmost care is taken. So at a fire in a wooden floored and timbered building, the risk is exactly known. Where iron is employed, doubt and danger are met; the floors or roof may fall in at any moment, and bury all beneath the ruin. Conclusion —The result of the foregoing would seem to be— 1st. That the so-called fire-proof and fire- resisting materials require improvement. 2nd. That some method of treatment is wanted that shall fully encase the iron, and so protect it from the action of the flames. 3rd. That all iron columns require also a similar casing. 4th. That where no such casings exist, iron is a dangerous and not a fire-proof material. 5th. That wood columns similarly encased are almost, if not quite, as fire-resisting. 6th. That the wooden floors by proper pug- ging may be made almost as fire-resisting as any of the iron systems, and will ,have certainly advantages as a set-off—namely, that should a fire occur, the firemen can with more certainty and security perform their labours. 7th. That the first cost is cheaper; if a fire occurs the reinstatement is cheaper. All these facts would lead one to hesi- tate before deciding to recommend one’s client to agree to the increased expense required by the various systems. Uncer- tainty and indecision may well be excused, and we may easily be induced to say, slightly varying the meaning of the poet— “Ah! what troublesdo environ, _ ns The man who meddles with cold iron. B®