Foundation questions

Started by archimedes, December 09, 2019, 05:32:29 PM

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archimedes

Hello,
I'm making plans to build a cabin in PA.  It will most likely have a full perimeter stem wall foundation below the frost line.  The cabin is going to be uninhabited, and unheated, during the winter.  Since it is unheated does this present a problem since the crawl space will be exposed to freezing temps and therefore expose the stem wall (at it's base) to freezing temps too?

If the crawlspace is unheated does that defeat the purpose of putting the stem wall below the frost line?
Give me a place to stand and a lever long enough,  and I will move the world.

Don_P

No, below frost depth the soils should not freeze and lift the foundation, it is not depending on heat from above.


archimedes

Thanks for the reply Don.

I'm from FL so this whole frost heave thing is new to me.

I'll be building, hopefully this spring, in PA.  I thought I remembered someone expressing a concern about leaving an incomplete house (just foundation no walls) over winter and how the foundation might be damaged from the cold.  I was thinking that no heat in the building might create the same concerns.  I could be just over thinking it though.

I've started to explore the possibility of an FPSF.  There seems to be a recommended method for FPSF in unheated buildings that might work.  That only seems to work though with a slab on grade.  I would like to have at least a crawl space.

I remember a while back about a build in Maine on this site, where they used a FPSF.  Unfortunately, that thread feel victim to the photobucket extortion.

Give me a place to stand and a lever long enough,  and I will move the world.

Don_P

FPSF's are more susceptible to heave, especially if unheated.
The problem with heave over winter during construction is often from the inside face. Right now I'm working on a house with a walkout basement. On the exterior we are backfilling so that side is below frost depth. The interior, we are looking at the top of the footings and the outdoor temps are indoors, so we are not below frost depth. We are on decomposed granular granite so I'm not really worried about moisture accumulating to the point where it can heave. If I was worried I'd stack square bales of straw around the interior of the basement until we have more temperature control. At the walkout we stepped the foundation down to keep the footings below frost depth on that non backfilled side, a "frost wall". If you are in an area of concern or worried about what it will do unheated measure your frost depth from the interior, lower, grade level. Also remember that in order to heave it requires moisture, good drainage is cheap insurance.