For heavily loaded foundations, using the allowable bearing capacity from Table 18.4 may be too
conservative for hard and sound rock, which will result in an uneconomical foundation. For exam-ple, Table 18.4 specifies a maximum allowable bearing capacity of 12,000 psf (570 kPa) for crys-talline bedrock. But other sources have recommended much higher allowable bearing values, such
as 160,000 psf (7.7 MPa) for massive crystalline bedrock (NAVFAC DM-7.2, 1982). Local experi-ence may even dictate higher allowable bearing values, but the allowable bearing capacity should
never exceed the compressive strength of the foundation concrete.