2012 IRC.....R403.1.4.1 Frost protection. Except where otherwise
protected from frost, foundation walls, piers and other
permanent supports of buildings and structures shall be
protected from frost by one or more of the following
methods:
1. Extended below the frost line specified in Table
R301.2.(1);
2. Constructing in accordance with Section R403.3;
3. Constructing in accordance with ASCE 32; or
4. Erected on solid rock.
Exceptions:
1. Protection of freestanding accessory structures
with an area of 600 square feet (56 m2)
or less, of light-frame construction, with an
eave height of 10 feet (3048 mm) or less shall
not be required.
2. Protection of freestanding accessory structures
with an area of 400 square feet (37 m2)
or less, of other than light-frame construction,
with an eave height of 10 feet (3048 mm) or
less shall not be required.
3. Decks not supported by a dwelling need not be
provided with footings that extend below the
frost line.
Footings shall not bear on frozen soil unless the frozen
condition is permanent.