# Stupid footer question

Ok, here comes the stupid footer question of the month. I've been researching info on constructing a garage and know that I have to have a footer below the frost line, which in my neck of the woods is 32 inches, my question is exactly WHAT has to be below that line. Does the entire footer need to be below as in a 8 inch thick footer has the top of the footer at 32 inches or does the footer just have to sit or have its bottom at the frost line.
I originally thought it was the first way but have since seen some inferences that it might be the second way. I want to do this correctly but if I can start the footer 8 inches higher I save on hand digging 16 x 8 inches of dirt and save on 8 x 8 inches of concrete for the stem wall thus lightening the load on my wallet and back.
Bill
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Top of the footing.
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Around here it is a 48" frost line and to the BOTTOM of the footing. Why the top? What if the footing is 2' thick? EDS
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I always thought the same though we never have to deal with frost lines where we build so I don't know. The way I understand is that SOMETHING has to sit on solid ground that won't shift to much, so if the bottom is below the frost line, the rest "should" stay relatively put. That's all pure assumption though, so take it with a grain of salt.
Basically here in California the frost line is above where a standard footing would be anyways, so we build em like normal. This makes me think that it's the bottom that must sit below the frost line.
--
Edgar

** Posted from http://www.teranews.com **
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wrote:

The frost line is an imaginary line and, hopefully, not the actual depth of frost - otherwise you're in trouble. The frost line is a design criteria and the footing should sit on undisturbed soil no less than the stated depth.
R
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Not above, at or below. I just checked with a structural engineer and the local Code. As Rico said it's an imaginary line, just get below it. As you get further North into deep snow country, it never gets below 6' as the snow is an insulator. However even further North in permafrost areas, the buildings must be insulated from the earth to avoid melting the permafrost. I worked on one project where we put in 2' of stone on the permafrost, and built a wood frame sitting on the stone to support the building, with a 3' space between building and stone. Another way is to set wood piles into the ground down to below the permafrost summer melt line, and build your structure several feet above grade. EDS
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More complete information: http://irc.nrc-cnrc.gc.ca/pubs/cbd/cbd026_e.html
R
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EDS wrote:

I've read some interesting things about floating foundations on permafrost in Siberia where the permafrost is becoming not so "perma" in some areas. In one ara what is made secure below the frost line is made secure by not disturbing the frost line.
study: http://www.springerlink.com/content/qj9v8exf77ger3xb / on: http://en.wikipedia.org/wiki/Permafrost scary: http://www.thewe.cc/weplanet/news/arctic/permafrost_melting.htm#this_is_real
Where were you building?

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The North Slope, DEW line facilities. Also a "hotel" at Thule AFB in Greenland. EDS
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On 10 Apr 2008, EDS wrote

And it's a real risk: I took a photograph in the late 1970s of a new house in Yellowknife that had tilted about 15 degrees at one corner when the developer got it wrong.
(My parents were working in Yellowknife at the time, and I went up there from Edmonton, where I was living, for Christmas. I moved to England in 1982, and I *still* have zilch nostalgia for that climate...)
--
Cheers, Harvey
Architectural and topographical historian
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EDS wrote:

That past few winters we've had little snow and brutal cold temperatures. A couple of winters ago, almost everyone's septic systems froze up. Frost down 7' in most places with a few reaching 8'.
Frost design depth here is 5'... But most people just opt for the additional small expense and go 8+' with a basement (unless they have water table issues).
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What possible reason could plant roots have to enter a nutrient rich water and sludge supply...? Nah - never happen!
R
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[snip]

Do sunflowers like to have "wet feet"? Maybe you should look into some native plants that like wet/boggy conditions...?
Problems with sunflowers in wet soil:
http://www.ag.ndsu.edu/pubs/plantsci/pests/e800w.htm
http://www.plantingscience.org/index.php ? module=pagesetter&func=viewpub&tid=2&pid13
How wet is your soil? Is it constantly wet, or intermittantly? Is the area in full sun, part sun, part shade, or deep shade? IIRC, you're in hardiness zone 6, is that correct: http://www.growit.com/bin/USDAZoneMaps.exe?MyState=in ?
THis part of the site allows you to enter as many (or as few) conditions are you require, and then get back a linked listing of good candidates: http://www.growit.com/PlantInfo/LandScape.Htm
Need more...?
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If you need someone to make a shop drawing for piece of rebar, let me know.
:-)
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Just remember this, if the rebar is shown on the drawing with a dashed bold line it doesn't mean that the rebar is to be installed in short separate little peace's.

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Since the footing supports the foundation wall or basement slab isn't it logical that the footing should be below the frost line so as to not be subject to the freeze/thaw cycles that occur above the said frost line?
That's the main reason...
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On Apr 10, 11:27 am, "Pierre Levesque"

The frost line is a design criteria, and, as with all design criteria, incorporates a factor of safety. If you want to pay more to build in an additional factor of safety by excavating deeper, well it's your money. The primary problem is the moisture in the soil, so if you have poorly draining soils, don't have foundation drains, and your gutters dump water next to the foundation then I would agree that going deeper is a good idea. Otherwise it's wasted money.
R
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Backfilling should be done with a structural fill not susceptible to freezing. A damp backfill with many fines just tossed back in will heave a foundation just by being frozen to it. I always backfill with gravel to within 8" of the surface, place a geofabric or tarpaper sloped strongly away from the building for several feet, and complete with topsoil. The geofabric or tarpaper keeps the fines from infiltrating the gravel and directs them (and some moisture) away from the building. Any basement in our climate (New England) should have drainage tiles set at the bottom of the excavation on a substantial bed of gravel, sloped to an outlet. In some cases I've used 2 sets of drainage tiles, one half way down. EDS
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<snip>

How do you guys handle a non-basement foundation?
Bill
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Just go down 4' and backfill same way. Usually no drainage tile needed. Most of my work is commercial work, so houses may be a bit lighter. The 4' is a given and I've done 6' in the Northeast Kingdom area of Vermont. Slabs-on-grade make for cold feet. EDS
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