This article is about residential concrete basement or foundation walls, but much of it applies also to nonloadbearing partition walls and other concrete walls above or below grade. Site planning, excavation, and design considerations are discussed.
Residential loads are usually small and do not cause any significant settlement in most soils. However, if there are organic soils, cohesive and sticky clays, or more than one kind of soil on the same site there could be some settlement problems. In planning how to use the site, provision must be made to drain surface water away from the structure. For a distance of 8 to 10 feet from the foundation wall the finished grade should slope « to 1 inch per foot. If the site is on a hillside it may be necessary to build a cutoff drain on the high side of the house to lead surface water away from the basement. On a low site the building should be built high enough to add fill sloping away from the walls so surface water will flow away in all directions.
General excavation is done with mechanical equipment. Good cohesive or clay soils should be excavated at least to the level of the top of the footing, and porous noncohesive or sandy soils should be excavated to the level of the bottom of the footing. Sometimes the exterior of the excavated bank serves as the exterior form for a wall of 8-inch or greater thickness. Normally, however, the excavated area should extend 2 feet beyond the outside line of each wall so that there will be working space for construction. If the banks are more than 6 feet high they should be stepped or tapered back.