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RE: footing - frost depth

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Frost lines vary from year to year and it can be a big difference in temperate climates.  One approach is to install horizontal rigid insulation about 4’ out around the perimeter.  This way any heat from mother earth can be contained and cold from the atmosphere kept at bay.  For applications where insulation is not used, piers or cip piles can experience frost jacking.  Depending on the frost susceptibility of the soil and available moisture in the soil mass frost jacking can be massive – 110-260 psi – check out work by Tsytovich in the late 50’s.  Lab results typically show 10 psi for wood and concrete materials.  A good idea is to sleeve piers and piles with sonotube or steel tubes through the frost zone.  For light structures this is problem.

 

From a long term concern, over time, as grading or vegetation on properties change, moisture can be added to a frost susceptible soil, so where you didn’t have a problem – one now has developed.  Some contractors are using glycol and heating pumps to cure concrete.  Some owners are purchasing the pumps during construction to use it for heating their walls as well as minimize frost problems over the long term.

 

 

----------------------------

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Hans E. Boge, P. Eng.

268 Ellen Street

Winnipeg MB, Canada, R3A 1A7

p:(204) 942-7276 ext 223

f:(204) 942-7288

www.boge-boge.com

hanseb(--nospam--at)boge-boge.com

 

-----Original Message-----
From: Jim Wilson [mailto:wilsonengineers(--nospam--at)yahoo.com]
Sent: Wednesday, March 22, 2006 4:12 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: footing - frost depth

 

The IRC states "...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. Extending below the frost line..."

 

Subsequently, the bottom of footing must be set at or below the frost line.  Some engineers and architects detail the top of the footing at frost line.  It's my guess that this is an older-school approach.  I say that only because I have seen it on older drawings, not in common practice.

 

For sloping grades, the footing depth needs to be measured perpendicular to the slope.  This could increase the vertical depth.

 

Jim Wilson, PE

Stroudsburg, PA

IRV FRUCHTMAN <ifaeng(--nospam--at)yahoo.com> wrote:

Dave
I thought the bottom of the footing is placed at or
below the frost depth.
Irv

--- David Topete wrote:

> List:
> Can someone give me a brief summary of foundation
> design (or detailing) with regard to frost depths
> noted? Do I basically place the top of spread
> footing at or below the frost depth? from finish
> grade?
> A reference would be just fine also. I rarely
> design for wind, snow, or frost, but there's a first
> for everything...
> Thanks in advance.
> DT
>
>
> ---------------------------------
> Yahoo! Mail
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