There are a number of types of concrete foundation walls now accepted in general use. Two are illustrated in Fig. 3. They are: first, the entire foundation wall of cement blocks; second, the combination wall (poured concrete to grade, and blocks or dressed stone above).
A wall of the first kind is shown to the left. Excavation for foundation of this kind is made in the usual way, deep enough to provide a foot ing below frost (3 to 5 feet down). It is well to make the footing twice the width of the wall, and 10 inches thick. If the soil is firm, as it should be, no forms will be needed for this, the concrete being poured into the trench to harden.
A special large-size block is good for the wall, 8 by 12 by 24 inches. These are laid up in the regular way with cement mortar. When finished, the wall may be thoroughly water proofed by painting the exterior face with a paint made of Portland cement and water. The inside of the wall should also be finished with a quarter-inch coat of neat cement.
The second type or combination wall is shown to the right in Fig. 3. This is very good, especially where the soil is firm; for, in that case, only the inside forms need be used. Excavation is carefully made, stopping just at the outside foundation line; the bank is hol lowed back in under, for a sloping footing below frost; and the inside forms are set up. Con crete, composed of 1 part cement, parts sand, and 5 parts crushed stone or gravel, is then carefully shoveled in and tamped solid. This wall will be waterproof, dense, impervious to water, if, before the Portland cement was used, hydrated lime in the proportion of 1 to 10 was thoroughly mixed through it. When this foundation has hardened sufficiently, the upper wall of blocks or dressed stone is laid up in the regular way.
Fig. 3 shows also two methods of framing for the superstructure—one for an ordinary frame building, standard construction, and the other for a frame building veneered with four inch-thick concrete blocks. These should be secured to the framework, either with patent anchors or with large spikes driven into the wood with the heads built into the joints.
An economical foundation wall sometimes used where the building code prescribes thick walls, is a combination of hollow block and monolithic construction. Its economical fea tures are not confined alone to the saving of concrete, but include the forms also, as scarcely any form is necessary for the footing; and after that the piers are built, requiring but a few forms, which can be used over and over again without resawing or wasting lumber. Fig. 4
shows the arrangement. Piers 6 or 8 feet apart are erected, using a grooved block. Between these piers the curtain walls are placed after the piers become hard.
On small work, where only two or three men are employed, no stop need be made if four piers and three sections of curtain wall forms are used.
The water-table is made after the piers and curtain walls are self-sustaining.
By the use of hollow blocks for piers and monolithic curtain walls, this method of con struction is surprisingly rapid and effects a great saving of cost, especially in localities where the hauling adds much to the cost of concrete.
The appearance of this wall is preferable to that of the straight plain type. Besides, when building codes class concrete with rubble stone walls in thickness, only the piers need be the thickness required, while the curtain wall is usually acceptable if six inches thick. Walls of this type have been made as light as four inches, and have stood every test.
ith this method, a single wagon carries all forms and tools from one job to another; the cost of the forms, made of siu•face lumber, is about $18.00, while the waste of lumber on a complete form for a dwelling foundation wall 30 by 40 by 7 feet high, for a 12 or 18 inch wall, will be $25, to say nothing of discoloring about $150 worth of good lumber.
By adding about one pound of ultramarine blue to each barrel of cement used for curtain walls, a beautiful effect is obtained, as it gives the piers and water-table a lighter color and more massive appearance.
Cement Cellar Floors. No matter what kind of foundation walls are used, the floor of the up-to-date basement or cellar is of concrete. The construction is very similar to that for cement sidewalks. No sub-foundation is, how ever, necessary as a general thing. Level and pack the earth surface and lay down 5 inches of concrete. Float smooth, giving all sections a slight slope toward some common drain point. When the concrete has become slightly hard ened, apply a half-inch top dressing of neat cement, or a rich cement mortar. This dressing should be rounded up in the corners and made continuous with the side wall finish.