There is another very serious evil, in building, to be guarded against. Owing to the moisture of the earth rising through the foundations and saturating the walls above, the health of the occupants of such houses may be seriously affected by its presence in the walls. About twenty years ago it was the universal practice in good buildings to place wide stone landings—three times the thickness of the wall above—under the foundations, for the purpose of preventing the damp from rising as well as to spread the width of the wall.
Section of a proper foundation for a wall.
A bed of concrete is now used as a substitute for this plan; the engraving below shows the best method of constructing foundation walls. A trench, three times the width of the wall is dug, at least 2 feet 6 inches in depth. Into this is thrown a quantity of concrete, which soon dries and becomes solid. In the superior class of buildings a layer of concrete, six inches in thickness, is placed entirely over the ground, inside the foundation. Upon this concrete the walls are built, the lowest footing being twice the width of the wall above. On a few courses above the top footing a course called a “damp course” is put; this is shown at a, page 152.
Two courses of slate are laid in cement; but other materials are often used, as a thin sheet of lead, for the whole width of the wall. Zinc might answer, but it has not yet been tried. A thin coat of asphalte, or asphalted cloth, tar, pitch, or a plain coat of cement are also often employed, but the two courses of slate in cement are considered sufficient. The first course of bricks above the ground is often formed entirely of air bricks, originated by Mr. Aldin, the builder, of Kensington. Each brick has eight or ten perforations, ½ inch in diameter, through its whole length; a small piece of perforated zinc is placed upright between the bricks to prevent insects from entering. This is shown at b. The timbers and stone flooring of the basement do not enter the walls, but rest upon dwarf walls, the joists having oak sleepers to rest on. The brick fenders of the foundations are entirely filled with dry rubbish or ironfounder’s ashes, and the stone hearths bedded solid either in mortar or concrete. This is the construction shown in all the designs of this volume. To illustrate still further the attention given in constructing foundations, the engraving below is given, showing a section of a foundation executed several years ago at Westminster, where the ground was uncertain. Its scale is only half that of the previous figure, the upper wall being 3 feet in thickness
Section of foundation to a wall.
instead of 1 foot 6 inches. Above the bed of concrete, which is 9 feet in breadth, by 3 feet in thickness, are York landings, a, 4 inches thick and exceeding 6 feet in width. Upon these are laid two lines of wood sleepers, b, bedded in brick and cement, the size of each sleeper being 12 by 6 inches, and in long lengths. Above this is a course of planking, c, placed diagonally across the wall; each plank being 12 inches by 6 inches, and about 9 feet in length. Above this are the footings, each two courses in height: in the return walls the landings, sleepers, and planking are placed a course higher, so that they might be tied together. The brickwork goes down twelve feet, and invert arches are turned at every opening.
In order to keep the walls as solid as possible in the lower part of a building, the ground floor joisting should rest on projecting corbel bricks as here shown,—the joists going between the cross walls rest upon projecting bricks, the upper one being of peculiar strength; tall piles are put between each joist against the wall, for the skirting in cement to be formed upon it. Air bricks in open iron-work, two to each front, are placed so as to admit air within the joisting.