Masonry Magazine September 1972 Page. 22
The details shown in Figure 2 were developed by the National Association of Home Builders and have proven to be satisfactory in wet locations.
Backfill Properly
If possible the excavation around the wall should be only a narrow vertical trench, so that when back-filling begins less pressure will be exerted on the wall than if the excavation is broad or sloping. Bracing of foundation walls is needed when there is a wide excavation to be backfilled, where there is much water or a fluid type of soil, or where walls are long. It is well to install temporary bracing supports on the inside as soon as the walls are laid. These supports may be simply constructed of lumber and stakes, but on jobs where there is need for frequent re-use, metal bracing frames may be more convenient.
Sod, frozen earth, trash, boulders, lumber or anything that can rot should be removed from the excavation before backfilling. Backfilling should be done with great care to build up the pressure evenly. Heavy earthmoving equipment must be kept from operating too close to the wall. It is always necessary to backfill parallel to the wall and not perpendicular to it.
The backfill should be built up above the adjacent grade to provide for expected settlement and for drainage away from the wall. The soil should not be compacted by watersoaking lest excessive hydrostatic pressure be developed. Bracing should not be removed until backfilling is completed and the first floor is in place.
NATIONAL CONCRETE MASONRY ASSOCIATION
P.O. Box 9185, Rosslyn Station, Arlington, Virginia 22209