I'm moving a deck footing for an existing deck, the current one is in the wrong location and it's too small. What is the proper depth in Connecticut in order to ensure that it doesn't suffer from frost heaving?
You need to place the footings deeper than the frost line. Some research says the frost line in CT is around 42" so you'd do well to put the posts down 48".
The city will be able to verify this when you get your permit approved.
Count yourself lucky... In Ottawa, Ontario I had to put them down 60"... and they still heaved one year.
(Amd) 1809.5 Frost protection. Except where otherwise protected from frost, foundations and other permanent supports of buildings and structures shall be protected from frost by one or more of the following methods:
- Extending a minimum of 42 inches below finished grade;
- Constructing in accordance with ASCE 32; or
- Erecting on solid rock.
Exception: Free-standing buildings or structures meeting all of the following conditions shall not be required to be protected:
- Assigned to Risk Category I, in accordance with Section 1604.5;
- Area of 600 square feet (56 m2) or less for light frame construction or 400 square feet (37 m2) or less for other than light-frame construction; and
- Eave height of 10 feet (3048 mm) or less.
Shallow foundations shall not bear or be installed on frozen soil.
I'm an excavation contractor in CT. Digging footings is one of my areas of expertise. The CT frost line is said to be 36" but rarely gets that deep. 42" is the standard requirement for footing depth, Many times people like to go up to 48" for good measure.