THE USE OF IRON IN HOUSEBUILDING.

New Zealand Times, Volume XXXI, Issue 4872, 2 November 1876, Page 3

THE USE OF IRON IN HOUSEBUILDING.

(From the Olasgow Herald). The report of Messrs. Hunt and Steward to the treasurer of St. George’s Hospital gives as clear an account of the cause of the bursting of the water-tank at the top of that building on the 3rd of June as if that event had been a carefully watched scientific experiment. As there is some reason to expect a fair crop of disasters from the causes of which the operation has been here so disastrously manifest, it may be well to state the gist of the report, stripped of the technical language in which it was very properly framed, but which is not familiar to the non-mechanical reader. The tank in question, which held between thirtythree and thirty-four tons of water, was made of cast-iron,plates, half an inch thick, bolted together in the usual way. The height of the tank was a little more than its width, the plan being a square of 10ft. on a aide, and the depth 12£t. The thickness of the iron plates was adequate to resist the strain put upon them only on the usual conditions of the use of the bars, which were made of wrought-iron, and nuts also : of adequate strength. But, instead of adopting the proper plan,of bolting these tiebars directly, to the flanges by which the plates themselves were bolted together, -thin plates pf wrought-iron, only Jin. thick, were bolted to these flanges, and the tie-bars were attached to cross pieces that ran through holes in these plates. The cross pieces were so short that on the least disturbance one end might slip out of its place, leaving the entire stress on the other end and, on the thin plate in which it rested; 1 As the whole of this arrangement was left in a situation most favorable for the corrosion of iron, and as it was nobody’s business to attend to the safety of the , tank, the natural consequence followed. The plates gradually rusted, and when the corrosion had advanced so far as to allow the bolt to be , torn; away by that strain on the sides of the tank which the cross ■bars-were -inserted to - resist, the tank tore in two landi the water made its escape. The general interest of the occurrence de- ■ pended oh the great and increasing use that has of late been madh : of iron,- both cast and wrought, in domestic building.-• Invaluable as it is when properly handled, iron is a very treacherous material when left to follow its own course without constant and competent inspection. It is often carefully embedded in the mortar of a'building without the slightest suspicion of the fact that from the moment of its being so embedded .it commences a slow but irresistible process that must result, unless provision be made to prevent it, in the destruction of the building it was intended to strengthen. Instances are familiar to the engineer of the splitting and bursting of brick-walls from the rusting of hoop-iron between the courses of bricks, which was inserted for the purpose of strengthening the : bond. 1 If the hrioks had been laid'in Roman cement no mischief would have ensued, as this material when set effectually prevents that chemical action. which lime mortar invariably occasions. One of the most striking instances that can be cited otthe alow but ultimate destructive action of iron plates inserted in a building was detected in the tomb of Henry VII., in Westminster Abbey, some ten years ago. Most of the metal work of that structure was either copper or bronze ; but at the four angles of the tomb’ itself, where the slab bearing the Royal effigy rested on the costly stonework of the sides, iron plates bad been inserted by way of bond. Slowly and steadily for three centuries and ahalf these iron plates attracted oxygen and. carbon from he atmosphere or from the mortar of the tomb, and coated themselves with dense ; plates of rust of three or four times their own thickness on either side. The result of this irresistible wedge was the twisting and rising of the rest of the work, and had not.these plates been removed when the grill was cleaned, they would sooner' of later have overthrown the tomb. We have here the case of the secular action of the same cause, of .which the more rapid and easily ascertainable action flooded the.hospital the other day,,: - i . ,With all our mechanical improvements, great as they are, we are as yet hardly the equals of 'our ancestors in permanence and durability of structure. We have lately come to regard iron as a safer material than wood. It may be safer than the miserable laths run up by unprincipled builders in what are falsely regarded as cheap houses—where the wood work is often properly fit for nothing but making matches. But not such was the buildings of the Tudor times. The massive beams of oak, scarcely squared, and hewn from whole trees, which formed the staircases,, the roof beams, and the other principal wooden portions; of the great mansions of Tudor times, such as Littleoote in Wiltshire, Loseby in Surrey, and many others that will recur to the reader, were and are to this day all but incombustible, both by their bulk and their position. Even now the Eondon firemen tell us how far more dangerous it is to enter a, house' of which the upper floors are supported by cast iron columns or girders, when on fire, than one supported by; solid , wooden pillars or beams; and this although such pillars are pow rarely made of oak; Gastiron when heated, . and suddenly : chilled, as when the jet of a fire-engine is turned on a burning, house, cracks like glass ; and many buildings have thus been entirely demolished by partial fires which would have done comparatively little damage if masonry or solid massive timbering Had been used instead of iron; and even if ultimately wood warning of the/coming, danger, which cast iron, .in such cases as we refer to, never does.; . Thus, on .the; one hand from water, and ; on-the other hand ? from fire, iron causes and.

suffers great peril and damage when employed as a.building material. And even when buried in masonry, or inserted as a bolt in solid stone (without being run round with melted lead) it slowly but: surely undermines the structure it was intended to protect. ■ ; > The outcome of all thin is the absolute necessity of a careful and regular inspection of all ironwork used in buildings. In cases where the exposure is most complete and the destruction most rapid, the ’safety of the inhabitants is the best protected. Under roofs such as those of the Crystal Palace, the dropping of the rain proves a ready detective of each new hole eaten by rust. Iron roofs which are open and exposed, as are those of most of our railway stations, are easily accessible for the purpose of painting, which is a protection never, safely to be neglected, and also have the good habit of proclaiming their need of the; painter, by unseemly stains. Buteven in these avowedly iron structures! great care is required in the regular inspection of each niinute,part, and in prompt renewal in case of' need. In all concealed ironwork, the danger is great. To; a certain extent,-the coating with zinc known as galvanising prolongs the life of iron ; but it is a protection not to be relied on without constant inspection. In fact, the natural’life of iron as a building material, as compared to that of sound brickwork, good masonry, or timber work, such as that which was employed in the mansions of our forefathers, is like the life of a, consumptive person compared with that of one in sound health.- Both are mortal; both are subject to : destruction from external violence. But each has, if exposed to none but the ordinary risks, its natural term of life, and that, of the man, or of the material, least subject to destruction and insidious corrosion, is by far the longest as such, as the most robust. Where 1 iron is needful it will always be used. What concerns the public safety is that it should not be used by persons ignorant or negligent of its essential character aud inherent danger; and that, by whomsoever and wheresoever employed as a structural material, it should never be left for twelve months without conscientious and.competent inspection.