Tony Hwang wrote:
slatts wrote:

Tim and Steph Wrote:
I live in Fairfax, VT, zip is 05454. I'm building a deck, and I'm going
to
be pouring concrete into sonotubes. Everything I've read states that
the
bottom of the sonotube must be below the frost line. Nowhere does it
state
how deep that might be. I assume that the USDA or the department of
snip...
Hi,
I am in Calgary. We go down 4 to 5 feet.
Local building inspector ought to know.

You got that exactly right. The magic number is whatever the local code
says it is and they aren't going to let facts about actual frost depth
into their considerations. In questions like this, it is always
mandatory to know what the local code says and then to stick to that or
go a little further. In the more restrictive codes they will also
require that the soil at the bottom of the hole is undisturbed
(generally worded something like "undisturbed mineral soil") and that
the area of the pour is sufficient to support the structure above.

--
John McGaw
[Knoxville, TN, USA]
http://johnmcgaw.com