13-132-060 Soil bearing values.

   (a)   Except when determined by field loading tests or by analysis based on laboratory tests, or both, the maximum allowable pressure on the supporting soils at the bottom of the footings shall not exceed the values established in Table 13-132-060(a) as set out in this section.

Table 13-132-060(a)
Bearing Values of Soils

Type of Soil	Maximum Pressure Pounds per Square Foot
Sand – compact and clean	5,000
Sand – silty and compact	3,000
Inorganic silt – compact	2,500
Clay – very soft	500
Clay – soft	1,500
Clay – stiff	2,500
Clay – tough	3,500
Clay – very tough	4,500
Clay – hard	6,000
Gravel	6,000
Hardpan	12,000
Solid rock	200,000
Organic soil	0
Filled ground or loam	500

 

   (b)   Exceptions to Allowable Bearing Values.

      (1)   Variation in Soils. Where portions of the foundations of the same structure rest upon soils which vary substantially in bearing value, special provisions shall be made to prevent serious differential settlements which will impair the safety of the structure.

      (2)   Where the bearing materials directly under a foundation overlie a stratum having smaller allowable bearing values, these smaller values shall not be exceeded at the level of such stratum. Computation of the vertical pressure in the bearing materials at any depth below a foundation shall be made on the assumption that the load is spread uniformly at an angle of 60 degrees with the horizontal.

      (3)   Subject to the approval of the building commissioner bearing values greater than those required in Section 13-132-060 may be used if analysis based on laboratory tests, field loading tests or other pertinent information demonstrate that the greater values will not lead to excessive settlement.

(Prior code § 70-2.4; Amend Coun. J. 9-13-89; p. 4604; Amend Coun. J. 3-5-03, p. 104990, § 30; Amend Coun. J. 11-13-07, p. 14999, Art. II, § 1)