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Concrete footings 101
Bearing capacity of soil
Understanding soil type and bearing capacities
Footing size
How to determine the minimum size for soil conditions
Footing problems
Pouring in wet soil and more
Frost heave & foundation footings
Frost protected shallow footings
Related Information:
Concrete calculator for footing pours:
Figure out how many cubic yards you'll need
Foundation drains for concrete footings

To use the simplified approach, the air freezing index (AFI) for the site location must be known. Insulation R-value and dimensions, and the depth of the footings are then determined from Table 2 and Figure 4. Horizontal insulation shall be bedded firmly on smooth ground or granular base. When foundation depths greater than 12 inches are required by Table 2, the increase in depth may be satisfied by substituting compacted gravel, crushed rock, sand, or approved non-frost susceptible materials.

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  • Insulation requirements are for protection against frost damage in heated buildings. Greater values may be required to meet energy conservation standards. Interpolation between values is permissible.
  • See Appendix for Air Freezing Index values.
  • Insulation materials shall provide the stated minimum R-values under long-term exposure to moist, below-ground conditions in freezing climates. The following R-values shall be used to determine insulation thicknesses required for this application: Type II expanded polystyrene - 2.4R per inch; Types IV, V, VI, VII extruded polystyrene - 4.5R per inch; Type IX expanded polystyrene - 3.2R per inch. NR indicates that insulation is not required.
  • Vertical insulation shall be expanded polystyrene insulation or extruded polystyrene insulation.
  • Horizontal insulation shall be extruded polystyrene insulation.

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