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delt (Structural) (OP)
23 Dec 02 13:45
What is the minimum frost depth for foundations for North Carolina?  Is this info. in the NCSBC?
boo1 (Mechanical)
23 Dec 02 15:45
The Standard Building Code average annual frost penetration list NC as ~5 inches (interpolating).  Which is less than the min. 12 inch foundation depth.
Helpful Member!  bylar (Structural)
23 Dec 02 15:49
You better check with your local building department.
NC is a large state and in the mountains we use 24" minimum frost line.
boo1 (Mechanical)
23 Dec 02 15:54
Thanks for the clarification, like is stated the code lists the "average" value.
LPPE (Structural)
23 Dec 02 16:32
Do what bylar said - check with the local building department.
StephenEd (Structural)
23 Dec 02 16:47
The info may be online. I looked up something similar for Cedar Rapids IA over the 'net last week. They had it in their local amendments to the 2000 IBC.

Be careful of using "average annual" frost penetration numbers. To me that means 1/2 the time you will exceed it!
Helpful Member!  RG88 (Structural)
27 Dec 02 7:57
North Carolina is under both the SBCCI and the 2000 IBC.  As of 1 Jan 03, the 2000 IBC will prevail and the SBCCI will be out of date.  According to Section 1805.2.1 of 2000 IBC, the min depth is 12" to avoid frost heave.  In Raleigh, I have seen frozen soil to a depth of 9" on January mornings.  In the past, I have discussed this with some of my counterpart inspectors in the mountains and they recommend 18" to 24", but enforce 12" as the code indicates.  No source is referenced in the code for an exact frost depth (table, chart, or otherwise).  I hope this helps, but like the others said, a simple call to the local Building Inspections Department will answer your question and give you a specific requirement for your project's location.  As a former inspector, I can say that we don't mind being asked questions as it is just part of the job.
delt (Structural) (OP)
27 Dec 02 9:07
Thanks all for the help.  I know the bldg dept is the best source, but no one was available at the time and I wanted  to be certain 24" was safe.  thanks a 10^6!
BantrelStructural (Structural)
7 Jan 03 18:51
Frost penetration and jacking/heaving is also a function of soil type, so (assuming that you have a geotechnical engineer on the project) he may be able to give you some site specific guidance.

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