BRICK FOUNDATION WALLS Thickness. Foundation walls are classed in building codes as all walls and piers built below the curb-level and which support the superstructure. There is no basic rule by means of which the thickness of a brick wall in proportion to its height is determined. The common rules for brick wall foundation thicknesses are that such walls shall be at least 4 inches wider than the walls which rest upon them. This thickness must be maintained for the first 12 ft. of depth of foundation wall, and be increased 4 inches for each 10 feet, or part of 10 feet, of additional depth.
The accompanying table on the thickness of foundation walls for buildings of various heights will be a safe guide to follow where no local building code is in force.
Good, hard, non-absorptive brick make good foundation walls. A minimum thickness of 12 inches is always assumed for brick foundations.
The thicknesses given in the table are based upon experience. They are supposed to have large factors of safety. It has been suggested that in any case the results of column-testing may be considered as establishing a definite line of strength, this being that the height of a column shall not exceed 10 times its least dimension. In column-testing, the column will buckle if this proportion is exceeded ; if it is not, full compressive resistance will be secured.