R403.1.4.1

Section R403.1.4.1 is titled 'Frost protection' and covers the requirements for protecting foundations from moving due to loads created by water freezing (and expanding) below the ground surface. Allowance for frost protection by any method (approved by the Building Official), a list of specifically defined methods allowed for frost protection, and clarification that footings may bear on permanently frozen ground is established. The purpose of this section is to prevent structural failure. This section has 3 exceptions which allow for certain type of structures of limited size or arrangement relative to the primary structure to not require frost protected foundations. The purpose of the exceptions is to allow for economical construction where the risks involved with structure movement are less severe.

The model shows a dwelling footing and foundation stem wall in the ground with a frost line depth represented by the solid plane. Viewing the model from a bottom angle shows that the footings were placed on ground which is below the frost line.