How to Calculate House Footing Sizes

Foundation walls usually rest on concrete footings, one of the load-bearing structural elements of house construction. Footings transfer the weight of loads to the soil beneath them; the weight spreads out to the soil around the footing The load-bearing capacity of the soil is the greatest factor in calculating the size of footings suitable for the weight of the house. The standard footing size is 16 inches square by 8 inches deep. A smaller footing size may be adequate for the load-bearing requirements, but the standard size allows construction of the forms and placement of the foundation wall.

House plans
CABO (Council of American Building Officials) Code; 1995
Local building code
Soils test (optional)

Instructions

- 1
  Check the house plans for the type of soil in the area or any soils report that exists for the property. Obtain a soils test that includes the allowable soil-bearing capacity of the soil if the information isn't already documented.
- 2
  Identify the construction method for the house. Find the recommended footing size in Table 403.1 of the CABO (Council of American Building Officials) Code for One and Two Family Dwellings by cross-referencing the soil type and its bearing capacity with the house construction description.
- 3
  Check the minimum width for footings required in the local building code and compare with the results from Table 403. If the footing is less than the standard size, consider enlarging the footing for ease of construction.

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