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USE OF MATERIALS, OR PRACTICAL BUILDING.
FOUNDATIONS AND DRAINS. 1881. In the previous chapter, the principal materials used in building have been enumerated; this chapter will explain how those materials may be most advantageously employed ; but we shall pot, in the various branches of practical building, again touch on the materials themselves, which have been already sufficiently described. The most important of all considerations—a due regard to the foundations on which a building is to stand—will be first ontered upon. The advice of Vitruvius may still be followed. In England, the recent introduction of concrete has superseded the use of wood under walls in the earth ; and piles are now quite exploded, except sometimes for the piers of bridges and other situations in which they can constantly be kept wet.
1882. The best soils fur receiving the foundations of a building are rock, gravel, or close-pressed strong sandy earth; " but," says L. B. Alberti, " we must never trust too hastily to any ground, though it may resist the pick-axe, for it may be in a plain, and be infirm, the consequence of which might be the ruin of the whole work. I have seen a tower at Mestre, a place belonging to the Venetians, which, in a few years after it was built, made its way through the ground it stood upon; this, as the fact evinced, was a loose weak soil, and buried itself in earth up to the very battlements. For this reason, they are very much to be blamed who, not being provided by nature with a soil fit to support the weight of an edifice, and lighting upon the ruins or remains of some old structure, do not take the pains to examine the goodness of the foundation, but inconsiderately raise great piles of building upon it, and out of the ararice of saving a little expense, throw away all the money they lay out in the work. It is, therefore, excellent advice, the first thing you do, to dig wells, for several reasons, and especially in order to get acquainted with the strata of the earth, whether sound enough to bear the superstructure, or likely to give way." It is impor cant, previous to laying the foundations, to drain them completely, if possible, not only from ho rain and other water that would lie about, but from the land water which is, as it were, pent up in the surrounding soil. In soft, loose, and boggy ground, the use of concrete will be found very great; and in these soils, moreover, the width and depth it should be thrown in should, as well as the lower courses of the foundation, be proportioned inversely to the badness of the soil. Clay of the plastic kind is a bad foundation, on account of the continual changes, from heat and moisture, to which it is subject, and which often cause it so to expand and contract as to produce very alarming settlements in a building. The best remedy against this inconvenience is to tie the walls together by means of chain plates, buried in the coutre of the footings, and on the top of the landings that rest on the concrete; those plates to be, of course, connected at the return. ing angles, so as to encompass the whole building. In these cases, the clay must be excavated to make room for the concrete. This will be found an effectual remedy in clay soils.
1883. By the Metropolitan Building Act, no building can be erəcted upon any site which shall have been filled up or covered with impure matter enumerated in the Act; it must be removed first, and any holes, if not used for basements, must be filled in with hard brick or dry rubbish. Generally, if the soil be a sound gravel, it will want little more than ramming with heary rammers; and if the building be not very heavy, not even that.
1884. Where vaults and cellars are practised, the whole of the soil must, of course, be excavated; but where they are not required, trenches are dug to receive the walls, which, in both cases, must be proportioned in strength to the weight of the intended superstructure and its height. In general terms, we may direct the depth of foundations to be a sixth part of the height of the building, and the thickness of the walls twice that of those that are raised upon them. Care must be taken that that which is to receive the footings of the walls be equable; otherwise, where external and internal walls are connected together, the former, being the heaviest, may settle more than the latter, thereby causing fractures, which, though not, perhaps, dangerous, are extremely disagreeable in appearance. The lower courses, which are called the footings of the wall, are often laid dry; and, perhaps, at all events, a sparing use of mortar in a spot loaded with the greatest pressure should be preferred. If the footings be of stone, very particular attention should be bestowed on placing the stone in the courses in the same direction or bed as it lay in the quarry, to prerent it splitting. The above mentioned Act requires that the foundations of the walls of every house or building shall be formed of a bed of concrete not less than
8 inches thick, and projecting at least 4 inches on each side of the lowest course of footings of such walls. If the site be upon a natural bed of gravel, concrete is not then required.
1885. In foundations where, from columns or small piers pressing upon particular parts, there would be a liability, from uneven bearing, to partial failure, it has been the practice, from a very early period, to turn inverted arches (see fig. 615) to eatch on their springing the weight to be provided against, by which means euch weight is equally distributed throughout the length of the foundation. "Standing thus,” says our master Alberti, “they (the columns or weights) will be less apt to force their way into the earth in any one place, the weight being counterpoised and thrown equally on both sides on the props of the arches. And how apt columns are to drive into the ground by means of the great pressure of the weight laid on them, is manifest from that corner of the poble temple of Vespasian that stands to the north-west; for, being desirous to leave the public way, which was interrupted by that angle, a free and open passage underneath, they broke the area of their platform, and turned an arch against the wall, leaving that corner as a sort of pilaster on the other side of the passage, and fortifying it as well as possible with stout work, and with the assistance of a buttress. Yet this, at last, by the vast weight of so great a building, and the giving way of the earth, became ruinous.” When inverted arches are proposed to be used, they should be shown in the drawings.
1885a. A method of forming foundations has lately come into vogue for bridges and other hydraulic constructions by the use of cylinders, or other shaped air-tight cases. In India the system of founding large masses of masonry on cylindrical piers built the interior of wooden curbs, has prevailed for a long period. The method of constructing the piers is the same as that used in England in sinking the steining for ordinary wells; and when sunk the interior is filled up with concrete or ruble masonry. Some of the iron bridges lately erected over the river Thames and elsewhere have been placed on foundations formed by cast iron cylinders filled in with concrete. Further details must be sought in works devoted to Civil Engineering, as the system will seldom be applicable in strictly architectural constructions.
1886. Air-drain. It is most important, when the walls are raised on the foundations, and brought up a little above the level of the earth, to take care that the earth, most especially if moist, should not lie against them; for if walls, before they are dry and settled, imbibe moisture, they rarely ever part with it, and thence gradually impart rot to the timbers throughout the house. It is, then, most important to have a second thin wall outside the basement walls, so as to leave between it and them a cavity for the
COURSE circulation of the air, such cavity being technically called an air-drain. In moist and loose soils it is essential for the durability of the building, as well as for the health of those who are to dwell in it. The Hygeian rock building composition, ly W. White, of Abergavenny, has been largely used for preventing damp passing through a wall. A wall may be built with half-bricks on the flat and set in this composition, filling the middle joint of half an inch, and an inch or so of each bed. This is stated to be much stronger than an 18-inch wall built in the ordinary way. A brick flat with a brick on edge, as for cottages, or for economy, is quite damp-proof, and equal in strength to a 14-inch. wall built with mortar only. No skill is re
CONCRETE quired; an intelligent labourer can use it.
1886a. It is important that the air-drain or dry area should commence at least as low as the foundations of the building; in very wet situations it should be provided with pipes to carry off the superabundant moisture, and be independent of the main drain of the building. Even when provided, the us” precautions to prevent damp arising in the main walls must not be neglected. The
drain, which should never be less than 8 inches wide, more if possible, is commonly covered with a half-brick arch, or with stone, slate, or tile, below the surface of the ground. This entirely does away with the benefit anticipated by its formation, because the surface drainage descends and injures the main wall, even when cemented above the covering; this covering should come some inches above ground. Unless care be taken it often degenerates into a hole for dirt and vermin. A good arrangement is to make a dry area, or a space wide enough to be easily cleared out, and to which a cat or dog can have access, and to cover it with stone with moveable gratings at convenient distances : the expense will not be much greater, while the result will be very effective. The most secure arrangement, however, is to form an open area all round the building. The want of such a precaution in the houses in the suburbs of towns renders a large majority of those having basements nearly uninhabitable from the disagreeable consequences of damp walls. (See also fig. 615h.)
18866. Damp courses. This simple provision to prevent wet, which is likely to get into walls, from rising in them by capillary attraction, is too often neglected, especially in cheap work, for the present saving of a pound or two; but at the ultimate expenditure of many pounds. The simplest plan has generally been to work three courses of the brickwork above the footings and below the ground floor, in cement. Messrs. Smith of Darnick state that a coating of cement, done in a very substantial manner, did not appear to have the smallest effect, as the wall was as damp above it as below. For small cottages they found an effective plan was to build all the parts of the wall underground quite dry, and not to use any mortar until clear of the earth. This left the walls quite dry above. The next method is to bed a course of sound whole slate slabs, | inch thick, in cement. When the soil is very damp, two or even three courses of ordinary slates may be laid in and well bonded, not only in the main walls, but in all cross partitions and dwarf walls. For some reason, probably that of the slates and cement having separated or crushed with the weight of the walls, allowing the damp to pass through, this method has fallen into disuse. As Portland cement will adhere to slate, probably, in solid works, if used instead of Roman cement, the result would be more satisfactory.
1886c. Sheet zinc bedded in loam has been found to decay. In extensive works, finegritted asphalte, applied in a hot state, is introduced as a layer, about half an inch in thickness. This material is stated, in the Appendix to the Report of the Fine Arts Commissioners, to have kept out the effects of damp, which would have shown themselves, as the foundations of the building referred to were always in water about 20 inches below the level of the ground floor. The brickwork should be dry and protected from rain during the operation, to prevent the asphalte becoming honeycombed. In buildings already erected, the walls can be underpinned to introduce the material. At the New Palace at Westminster the joints are only half filled with mortar, the asphalte filling the remainder when poured over the bricks. The bricks for the next course, having been heated at a coke fire, were placed on the asphalte in its fluid state, and the joints half flushed up. The outer courses, however, should be first laid for short distances, that they may set before the middle is filled in. In rubble masonry, it will be necessary to fill up all inequalities on the surface with fine concrete; when this has set sufficiently, the asphalte is to be laid as described for brickwork. Gas tar mixed with lime is said to be impervious to wet.
1886d. Two centu ago, thin sheet lead was laid on the top course of a wall to prevent damp coming down it from the gutters; of late years, a layer of 4 lb milled lead
Fig. 615e. has been proposed to prevent it rising; no doubt the best and most efficacious remedy, but the cost would be greiter than usually allowed. But the best invention, baring price also in its favour, is the damp-proof course, formed of brown stoneware, perforated throughout its entire width with a half air space, which remains open after the mortar beds are laid, on each side of the slab. In an executed work, a course of bricks can be cut out and the stoneware be inserted. This is one of the many building inventions of Mr. John Taylor, junior. Fig. 6156. shows one for an 18-inch wall; other sizes as well as angle blocks are provided. Each foot superficial is stated to be equal to the support of 25 tons or 600 feet of vertical brickwork. “Jennings has patented earthenware sleeper blocks, "non-conductors of damp and a cheap substitute for brick sleeper walls;" they
draing. Ordinary street sewers are built of hard bricks set in cement, and are now
the Metropolitan Board of Works; and no drain can be laid into a sewer without the previous approval of the vestry or district board, which has to apply to the Metropolitan Board of Works for their sanction in both cases. Many towns in England have now their Board of Health supervising the drainage of the streets and houses, pursuant to “The Public Health Act, 1848,” and “The Local Government Act, 1858."
are also useful for carrying stone paving: figs. 615c., 615d., and 615e. describe themkeltes. Fig. 615f. shows the section of a sleeper-wall in brickwork, carrying stone paring on one side and timber joist on the other. There are four courses of brickwork, on which is laid the timber sleeper, 4 inches by 3 inches, to carry the joist.
1886e. Fig. 6156. is also useful for admitting air into the space under a floor, and then dispenses with the common
cast-iron air-brick usually fixed for such a purpose. Air grat- ings are of a larger size. The following arrangement, shown in
Figs. 615g. and 615h., has been carried out where it was thought - advisable to provide for the admission of a large quantity of
fresh air at times into the body of the building. Funnels or pipes were inserted in the side walls under the floor, say 1 ft. 9 in. diameter. An area protects the front, to which a small Weeping drain is put to carry off any rain water, and is
Fig. 615f. tected at the top by
a grating to prevent animals getting in. On the inside is a plate or slide, which can be let down through the floor, paring, or boards into a groova,
to regulate the quantity of air or to shut it : off. The fresh air ascends through gratings, or by other means, in the floor, into the hall.
1886. A preventive against the rise of damp in the inside of the building is to cover the whole area within the walls with a layer of concrete, about 4 to 6 inches thick. By a byelaw of the Metropolitan Board of Works, the site of every house or building shall be covered with a layer of good concrete at least 6 inches thick, and smoothed on the upper surface, unless the site thereof be gravel, sand, or natural virgin soil. But as concrete, especially if of a coarse character, is of a honey-comb character, even when fixed or set, being full of littlo cavities, there is some danger in placing
Fig. 6.5g. it in wet soils, for it will often weep, and if cut, water will be seen to ooze through it. Also, when placed under a basement foor to keep out damp, water will invariably find its way through if there be any pressure, as from springs. To prevent rapours rising from decomposed matter in the soil, a good practice, even in dry localities, is to cover the soil, before the floor boards are laid, with a layer of two. inches of unslaked lime, which on slaking with damp, or damp air, will destroy any Vegetation that may have been left on the surface.
1887. Before a brick or stone of any building be laid, the architect neglects his duty should not be by the aid of a stagnant tank, called a cesspool, if it can possibly be avoided, although there are some localities where such a tank must be formed, and then the solid contents can possibly be made useful for manuring purposes, the surplus water being drained off, possibly into some running stream at a distance from the building, whose exhalations shall not be blown by any prevalent winds of the spot back upon the place is much involved in good drainage as is the health of the family whose dwelling-placo capital in Europe. The lines of sewers forming the Main Drainage scheme have relieved elet and alley has its public sewer, and nearlyerery house has its separate drain into
No new sewer can now be made in London without the previous approval of
SEWERAGE AND DRAINAGB.
9 inches at the bottom, of the sides, which are formed by curves of a large radius, and 6 feet high in the clear. Smaller sewers are 2 feet 9 inches and 2 feet 3 inches wide, and 4 feet 6 inches clear height; and 2 feet 6 inches wide, and 4 feet clear height. The
smaller end is placed downwards. The difference of friction or impediment in favour of a curved bottom is great, much power of the flow of water being lost by the use of a flat or flatly curved bottom. This part of the sewer
is called the invert, and is often formed of 2' 6"
stoneware, the core being filled in with coarse cement; thus the foul liguid does not percolate through them into the soil. The figure (615i.) shows Jennings' compound invert blocks, laid and jointed in Portland cement; the bricks at the angles set in blue lias lime. Smaller sewers are now made of large circular glazed stoneware pipes, and in a few exceptional instances of iron; and even rock concrete tubes, from 15 inches to 36 inches
diameter, are made at Poole. The joints of Fig. 6151.
these pipes are made watertight. These ordinary sewers pass into larger ones called "main sewers," all gradually inclined from the higher to the lower levels, joining one another either with curves or acute angles, so that the flow of one current shall not impede that of another; and they gradually become larger and larger, according to the requirements of the town, until they end in one or more outfall sewers discharging into a river, or to reservoirs for a system of irrigation or for other purpose.
18876. The accumulation of foul deposits in sewers is caused by the want of sufficient fall or sufficient flushing with water, and so occasions foul air, or gas as it is wrongly callod. Hence it is essential that the sewers should be well ventilated, in order that the foul air shall not escape or pass up the drains of the houses. This ventilation in a line of sewer is effected by a shaft carried up from the crown of the sewer to the surface of the street, where it is finished by a grating. Where there are plenty of these ventilating shafts, it is considered that no nuisance is produced by the bad air as a general rule, because the purer air is supposed to be continually passing into and out of the sewer through them, thus diluting the foul air. If a nuisance from foul air is complained of, it would show that something was wrong with that part of the sewer, or that another ventilator was wanted in the distance between the two already in position. Instead of these, it has also been proposed to ventilate sewers by means of pipes carried up houses and ending above the roofs, but this system is considered to be inefficient unless the pipes are of large size. The head of a system of sewers, or the end or head of a sewer, as to a court of houses, requires both a Hushing apparatus to occasionally cleanse the sewer, and a pipe ventilator or ventilating shaft carried up to carry off the foul air which there collects. Other systems have been suggested. Various attempts have been made to create strong upcast draughts by furnace chimneys, cowls, or other artificial means, but these attempts have never been more than locally—and then only partially—successful.
1887c. Whilst on the subject of sewerage, it may be well to refer to the new system of raising the sewage from a low to a higher level by means of Shone's hydro-pneumatic sewage ejector. This successful system, as carried out at the Houses of Parliament, is described in the Transactions of the Royal Institute of British Architects, 1887, iii., new series, and in British Architect for January 28, 1887. p. 69. The work was performed thus: in the bottom of the old main brick sewer, about 1000 feet long, passing from north to south under the Houses, a 12-inch cast-iron drain was embedded in concrete, with a fall of about 1 in 212. This received all the sewage of, and rain falling on, the Houses and grounds, and was discharged into a receiver at the bottom of a sewage manhole. From the side of the receiver a 12-inch cast-iron inlet pipe is carried horizontally into the adjoining ejector chamber, in which are three cast-iron ojectors, one being capable of discharging 480 gallons, and the other two 335 gallons each, per minute. The sewage is conveyed into them by a 6-inch cast-iron pipe. From the bottom of each ejector a 6-inch cast-iron pipe passes vertically upwards into a 12-inch cast-iron horizontal outlet pipe, which is carried through a dam built in the old main sewer, and discharges beyond it into the old outlet communicating with the Low Level Sewer, and above the normal flow of sewage therein.
1887d. Compressed air is used for ejecting the sewage, &c., from the ejectors by Atkinson's differential gas engines-four of them, each of 4 horse-power. Usually one only is employed. There is an automatic arrangement for conducting the air, and ball valres for admitting and expelling the sewage. The compressed air in the ejector is discharged by a pipe leading into the ventilating shaft passing up the clock tower. Ti