Design provisions for strip foundations

The following design provisions apply – (a) the foundation should be situated centrally under the wall; (b) the foundation should have the minimum width given in Table 4E.1; (c) the minimum thickness T of concrete foundations should be 150 mm or P, whichever is the greater, where P is derived using Table 4E.1, see Diagram 4E.1(a) and (b); (d) where the foundation is stepped on elevation, it should overlap by twice the height of the step, the thickness of the foundation, or 300 mm, whichever is greater (see Diagram 4E.2). For trench filled foundations the overlap should be twice the height of the step or 1000 mm, whichever is greater; (e) the step in a foundation should not be of greater height than the thickness of the foundation (see Diagram 4E.2); and (f) the foundation of a pier, buttress or chimney should project as indicated in Diagram 4E.3, the projection X should be not less than P.