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Aoa. While designing foundations for building and other structures, allowable bearing capacity is used to calculate required area (spread) of footing. There are two approaches of structural engineers, regarding value of allowable bearing capacity, actually to be used. First approach says that the weights of soil below ground level and the footing concrete must be deducted from the allowable bearing capacity value given in the soil investigation report, to determine net bearing capacity. This net bearing capacity is to be used to be used for calculating footing area required to support the load from superstructure. The second approach, says that NO deduction is required for soil and concrete below ground level, because: a. soil investigation is carried out while original soil over burden is in place, and only superstructure load is to be carried out by the foundation, b. Allowable bearing capacity given in the soil investigation report is very conservative, as it is commonly calculated by employing a factor of safety of 2.5 to 3. The first approach results in comparatively larger footing sizes. The question is, which of the above two approaches should be followed? And, why (code or some other references)?