Frost protected shallow foundations and long term vacancies.

[Darren Emery]

One thing I've always wondered as we see more and more FPSF homes: what happens if the home is unnoccupied and unheated for weeks or months? With all the forclosures over last few years, has anyone begun to see foundation problems with homes in their area that were built recently with FPS foundations?

How long might it take to begin to see frost heave under a home that has lost all heat sources. A few days? A week? A month?

I've considered a SFPF for my own home, but we lose power here in Kansas due to ice for extended lengths of time (over a week two years ago) - and I don't want to risk the foundation problems.

Any thoughts or experience to share on this topic?

 

[mtlogcabin]

There is a lot of varibles in your question, soil type being the big one, We are at a 36" frost depth and where there is clay it is a problem, solid rock no problem.

If you are considering a SFPF for your home I suggest you get a copy of ASCE32-01 "Design & Construction of Frost-Pretected Shallow Foundations" and look at the section that deals with un-heated buidings

Asce 32 01 Free Download PDF

I did this on my walk out basement but I have radiant floor heat so depending on the outside temp I could loose heat for a week or more and not worry about frost heave.

 

[Min&Max]

One contractor was building with SFPF here for awhile but it wasn't long before the contractor decided they were not as cost effective as touted. To me they looked like a huge PITA to form and pour. I was always concerned about the issues that Darren brought up but never witnessed any first hand.

 

[Architect1281]

The only reason a FPSF works is because the structure looses enough BTU's to keep the ground from freezing. absolutly counterintuitive to all the BTU police tactics to preserve them. When you turn off the heat and de occupy the frost move in and the structure will move unless the soil below is so pervious that moisture collection is not possible.