In the absence of tests the different soils, excluding mud and quicksand, shall conform to and shall be assumed to sustain safely the following loads per square foot, and footings shall be provided under all walls and columns where required to keep the pressure on the soil within the limits specified in this section.
Soft clay 1 ton
Firm clay, fine sand or layers of sand clay, wet conditions 2 tons
Clay or fine sand, firm or dry 3 tons
Hard clay, coarse sand, gravel 4 tons
Soft rock, shale and hard pan 8 to 15 tons
Rock 15 to 72 tons
('72 Code, § 151.029) Penalty, see § 10.99