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RE: Footing bottoms relative to the frost line

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Thanks for the response.  The 1996 NBC (BOCA) appears to be the only code
I've found so far that states "...shall extend to the frost line", the UBC,
SBC and 2000 IBC state to extend below the frost line.  Any thoughts on
interior column or wall footing depths?  Should the embedment depth be the
minimum required for footings not subject to soil freezing, as in most
structures temperatures are typically kept above freezing at the interior
(right now I'm thinking of an enclosed above grade parking area below
residential space with garage doors opening from time to time during cold
winter days)?

Albert J. Meyer, Jr., P.E.
Martin Engineering
(215) 665-8570 Tel
(215) 561-5064 Fax
ameyer(--nospam--at)martinaia.com


-----Original Message-----
From: TBenson(--nospam--at)lowney.com [mailto:TBenson(--nospam--at)lowney.com]
Sent: Tuesday, February 12, 2002 10:12 PM
To: seaint(--nospam--at)seaint.org
Subject: Re:Footing bottoms relative to the frost line


Albert,

1998 CBC and 1997 UBC Section 1806.1 says:

"shall extend below the frost line."

Does this mean 1-, 6- or 12-inches below the frost line?  I don't know. (But
I
will say: most of us geotechnical engineers work for the most part in feet,
not
inches).  It seems to me that depending on the jurisdiction and the amount
of
historical frost depth data available for your site, you may increase or
decrease your embedment accordingly as a function of frost depth
uncertainty,
structure importance, drainage, silty sands versus sound granitic bedrock,
heating and insulation, topography and exposure, etc.  Check your local
building
official (if you haven't already).

Tom Benson at Lowney Associates
251 East Imperial Highway, Suite 470
Fullerton, CA 92835-1063
(714) 441-3090
FAX: (714) 441-3091
see: www.lowney.com
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____________________Reply Separator____________________
Subject:    Footing bottoms relative to the frost line
Author: seaint(--nospam--at)seaint.org
Date:       2/12/02 1:43 PM

I have a question that a few different engineers and architects have
provided different answers for.  When I have been given the frost depth for
a particular building site, I, and some other engineers I have talked to
consider this line the minimum depth at which the bottom of the footing can
rest.  Some others have suggested that this is the location at which the top
of the footing must be placed.  Any opinions about this?  It is my
understanding that the frost line is just a best guess depth based on
historical data with some margin for error on the conservative side.

Albert J. Meyer, Jr., P.E.
Martin Engineering
(215) 665-8570 Tel
(215) 561-5064 Fax
ameyer(--nospam--at)martinaia.com


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