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.
Plan Of Course-1.
Plan Of Course-2..
Fig. 10. Flemish Bond 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.
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.
Coursed Ashlar Facing'.
Fig. 11. Types of Stone Work
In rubble work the stones are rough and unhewn. They must be laid upon a good bed of stiff mortar with their stratifications in a horizontal position. Otherwise, the face of the wall might "peel" from the effects of frost and moisture, making an unsightly as well as a weaker wall. The term "ashlar" refers to a wall builded of stones having finished faces. When either rubble work or ashlar is laid up in courses it is known as coursed rubble or coursed ashlar. When the horizontal joints are not continuous the wall is known as random rubble or broken ashlar.
Fig. 12. "Form" for Concrete.
Not infrequently a wall will be constructed with an ashlar facing attached to a brick backing by means of metal bonds. In such a wall, the faced ashlar, unless more than 8 inches in thickness and well bonded into the wall, should not be considered in esti mating the strength of the wall.
In the construction of both brick and stone walls the work should be carried up as nearly as possible at the same levels. In both brick and stone walls the corners are run up with stepped courses, the corners being plumbed as the wall is carried upward. A line is then stretched between the corners and, layer by layer, the rest of the wall filled in. No corner should, ordinarily, be carried more than 3 feet above the rest of the wall. In the case of un-coursed stone work the wall is leveled every 15 to 18 inches in its height.