456 BUILDING (BUILDING TRADES. Coring. Use of timber. Weather- boarding. Brick and timber fronts. Building trades. tions and enclosures should bo of oak ; though it is desirable that main bearing timbers, in situations which render them most liable to be exposed to the action of fire iu the event of casualty, should be of such timber rather than of fir ; but the quarterings, or partition timbers, which the plaster concrete wholly encases, may be of fir as safely almost as of oak. The core used in Paris consists for the most part of chips and spalls arising in the process of dressing the soft free stone which is the main constituent of the walls of most buildings in that city. Almost any hard material, however, will furnish rubble fit for the purpose, which must be angular and irregular in form, so as to allow the mortar to pass freely through the rubble, and embed it all. Rubble of brick material, as broken burrs, or even of old bricks freshly broken, will answer very well ; but if brickbats or shreds of plain tiles be used, care must be taken in packing not to bring flat beds together, or the mortar will not pass through and make a perfect concrete. Rubble of almost any kind may be used ; but the kinds of stone which are themselves concretions, and present rough surfaces upon the fracture, are the best, while schistose or scaling slaty stones are the worst for the purpose. But there is no better substance for coring partitions upon the plan described than clay burnt into a kind of brick rubble. The same process applied to external enclosures will justify the use of timber in their structure in situations and under circumstances in which it may be properly prohibited when the timber is merely lathed and plastered, or even brick-nogged, for brick-iiogging adds nothing, as already remarked, to the strength of a partition or an enclosure, but rather takes from it, being itself a source of infirmity. But chimneys and their flues, with their con geners, stoves and furnaces, ought not, under any circum stances, to be formed in an enclosure in which timber is employed as a part of the structure. Under some circumstances, again, that is to say, when any street of a town is so wide and the buildings to be built fronting it are to be of such small elevation, as to make the communication of fire from one side to the opposite side practically impossible, if the buildings adjoining laterally are effectually separated from one another by sufficient walls, party or otherwise, and these project before the outside faces of the front and back enclosures so as effectually to prevent fire from passing round them, the temperature of dwelling-houses may be much more easily maintained and regulated if the outside surface be boarded. Weather-boarding is a safe and economical, as well as a neat, wholesome, and equable outside casing for the fronts of a dwelling-house, if the boarding be backed up solidly, and the timber quarterings necessary to secure it be properly filled in between and behind with brick or stone work, or with rubble and concrete in the manner already described. Brickwork builds up badly with the raking braces of timber-framed enclosures, and the concrete described would not be so perfect with weather-boarding on one side as if the mortar were thrown in from both sides ; but raking braces are less essential to enclosures which are filled in and backed with a heavy body of brick work or concrete, than when mere lathing or even brick- nogging is to be employed on the inside. A 9-inch brick wall may, indeed, be very well built up with framed quarterings without raking braces, if the work be built between and around the quarterings, carrying, that is to say, the inner half-brick before the inside faces of the quar tering, and so as to show on the inside a plain brick wall. Building Trades. The artificers whose trades properly belong to the builder s business are the digger or excavator, bricklayer, mason, sawyer, carpenter, joiner, cabinetmaker, slater, plumber, plasterer, modeller, carver, glazier, smith, founder, ironmonger, gasfitter, painter, and decorator. In this order the works of the trades will be described, and we now proceed to the ordinary routine of the practice of building. The two publications which should be noticed here as comprising more detailed references to these trade;; are Gwilt s Encyclopedia of Architectiire, 8vo, 18G9, edited by Wyatt Papworth ; r.nd Cresy s Encyclopedia of Civil Engineering, Svo, 1861, these will not, therefore, be noticed in the list at the end of each trade. Foundation.- The architect having furnished the specifi- Fouuda- cation and working-drawings of his design, the first step tiou - is to prepare the foundation ; and as this relates to the bricklayer as well as to the mason, we say what is necessary respecting it here. Much in this particular, it is evident, must depend on localities. It is not of so much importance that the ground be hard, or even rocky, as that it be com pact, and of similar consistence throughout ; that it be so constituted as to resist entirely and throughout, or yield equally to the superincumbent weight. But in the ordinary processes of building little requires to be said of the artificial preparation of foundations beyond the notice of jt already given. When a good, hard soil is easily accessible, as solid gravel, chalk, or rock, we have nothing to do but to remove the surface mould, dig to the sound bottom, and at once to put in the footings. On softer ground it was usual to employ footings at least double the width of the wall, and frequently more ; but since the invention, or rather revival, of the use of concrete, this is seldom or never done. In this case, or when the ground is a deep clay, be the material used what it may, it should at least go so deep as not to be affected by change of temperature, or the rising and falling of springs, as the alternate shrink ing and swelling of the ground must affect the building. Frost seldom penetrates a foot into the ground in this country ; but in clay soils, fissures, the consequences of drought, are found 3 feet and more in depth. The basis should, therefore, be below this point in such a stratum. If the ground be springy, it should be drained, if possible ; if not, a foundation should be made with concrete as low as the lowest level of the water; or if very deep or boggy, piles must be used. The plan of building on sleepers and Plankii planking, so common some years ago, is very bad, as they rot after a time, and the building settles in all directions, as the greater weights crush the decayed timbers sooner than do the lighter portions of the building. Where ground is alternately wet and dry, the best timber soon decays ; even piles should always be kept in the water. The use of concrete, except in very peculiar cases, has entirely Concrc superseded every other artificial foundation. It may be defined as a sort of rough masonry, composed of broken pieces of stone or gravel, cemented together with lime prepared in various ways, and thoroughly mixed with it, and not laid by hand but thrown at random into the trenches, to form the depth required. Any hard substance, broken into small pieces, will make good concrete. That most used is gravel, or ballast. This should not be too fine, as the sand which may be in it will mix with the lime and form a sort of mortar, assisting to cement the stones together. If broken stones or masons chips are used, it is desirable to add some sharp sand with them. The general rule is, that no piece of stone should exceed a hen s egg in size. In this country the lime is generally ground, which is bad, as the core or unburnt portion is ground up with the good lime. About one-sixth part of lime is generally used ; chalk lime should not be used in a clamp situation. It is mixed with the ballast by scattering it among the stones, and turning it all over with a shovel, water being at the same time thrown upon the mass. It is then, while hot,
filled into the trenches, sometimes by shooting from stages