R403.3

Section R403.3 is titled 'Frost-protected shallow foundations' and covers the requirements for protecting a foundation from frost heave without extending it below the frost line. The minimum interior monthly mean temperature to allow for shallow foundations, a cross-referenced figure and table to which a frost-protected foundation must conform, and disallowance of a frost-protected shallow foundation from being adjacent to unheated or inadequately heated construction or space is established. The purpose of this section is to prevent structural failure.

The model shows a shallow foundation meeting or exceeding the parameters from row 4 of table R403.3(1). The extruded polystyrene insulation has an R-value of 4 per inch, is 2" thick for the vertical and horizontal wall pieces, and 2-1/2" thick for the horizontal corner pieces.