Fig. 9. English Bond
In many communities the use of concrete is supplanting that of stone or brick, especially below the grade line. Such a wall should be composed of 5 parts of crushed stone or gravel, 3 parts sand, and 1 part cement. The footing may be formed by tamping the mixture in a form made by spading out of the earth a depth and width sufficient for the wall to be supported.
5. Foundation Materials; Construction.—Of the materials commonly used in the construction of foundations monolithic concrete is becoming the most common for that part of the wall which lies below the ground or grade level. Brick and stone are sometimes used.
Where brick or stone is made use of, some device is required to "tie" the material together, due to the fact that the mortar used in filling the voids or spaces between the members has little strength as compared with that of the stone or brick itself. This bonding is secured by placing the brick or stone so that they shall overlap one another, both along the faces of the wall and across the wall.
Bricks laid with their lengths in the same direction as that of the wall are known as stretchers; those laid with their lengths across the wall are known as headers, [Fig. 8.] The manner of placing these headers among the stretchers determines the type of bond. The American, English and Flemish are the more common types. Of these the American, [Fig. 8], is the most used upon ordinary work. It consists of a course of headers placed every sixth course. The English bond, [Fig. 9], is much stronger, having every other course a header course. It is used mainly upon very important work where unusual strength is required. Flemish bond is illustrated in [Fig. 10.]
Fig. 10. Flemish Bond
Of the various types of stone work, rubble work and ashlar predominate, [Fig. 11.] Rubble work is most frequently used for that part of the wall below the grade line, and ashlar for the remainder of the wall. In either case, thru stones are placed every 4 or 5 feet in the length of the wall and every 18 inches in the height, to provide bonds.
Fig. 11. Types of Stone Work