I have a house in a region which is prone to deep frost, and is supported on cement piers. Some of these piers move up after the ground freezes, and then somewhat return after the ground thaws. Some of them sink past their original positions and require shimming to keep the house plumb. I'm currently applying basic drainage principles to get the water away before the ground freezes.
Someone suggested I bury styrofoam discs around the surfaces where my cement piers meet the ground to help prevent the piers from rising and shifting due to frost. Any thoughts on this?
I feel you would only be wasting your money. If this is a mob, and was installed in a last few years, you go back on the installer for failing to locate the footings below the frost line (a code requirement). Most allow you to sue for not complying with a major code item; some have limitations such as ten years, others shorter and others never expire. You should talk with your local building department.
If your home has a conic foundation you 'could' consider adding a little heat to raise the under-floor temp on the dirt; during the worst winter weather (this is only feasible if you have an enclosed foundation, not a curtain wall or skirting as the heat loss is going to be quite high).
As I see it, your only real option is to replace the piers, on-at-a-time with footings below the frost depth (leave the existing piers in place and install new piers along side; removing the original piers afterwards.) You WILL need a Professional Engineer to do this as there are many factors concerning the soil type, vertical and lateral load paths and existing structure to be concerned with). This would be a labor-intensive and a very costly venue; however you will never have a home that will resist frost heave with your current installation. Sooner or later it will cause serious structural problems.
Again, your local building official could be of immense help to you, please go there first and forger any easy scheme to fix a very serious problem.
Yes, buried foam can be used to prevent frost penetration. Here in Northern Minnesota, it is done all the time, and it does meet code (although an engineer has to sign off on the design). It would be no small matter to retrofit foam, however, on a house on piers. For it to be effective, it must be buried. Also,it'd likely have to be a pretty big "disc"--I have built several houses on shallow frost protected slab on grad foundations, and the typical detail we see (which will vary by climate) is 3" of extruded polystyrene 4 feet out from the house (granted, I practically live in the subarctic). If you really want to do it according to Hoyle, you should talk to an engineer who is familiar with frost protected footings. On the other hand, For a sample of what you are up against, check out
Thanks for the quick response. I don't see litigation as a solution to this problem. I bought this house in Northern Maine as a unfinished- fixer-upper, and knew what I was getting into.
The house is a large contemporary style home built on a southern slope, with the front of the house facing south. The large 1400' shed style roof "sheds" ALL of the water to the north side, which then obviously runs down the slope, and under the house. You'd think someone would've considered that, and built in some type of drainage system. I guess that's where I come in.
I'm applying some basic common sense things, like gutters, increasing the grading around the house, etc... I'm also enclosing and insulating the crawl space (where the piers are) under the house to help keep it warmer, and help mitigate the freezing/thawing cycle. And, just for kicks, I'm installing some salvaged glass sliding doors along the entire south side of the crawl space to take advantage of the sunlight and see if I can capture some heat under there. Sounds ambitious, doesn't it?
That's good info. I too am in subarctic conditions. I've got some styrofoam panels on hand to try it out. I was toying with the idea of digging down around the piers in the shape of the disc, lining the hole with some scrap typar, and filling it like a mold with that expanding foam (great stuff). I know, sounds like a lot of unneccesary work doesn't it. I was thinking it might adhere/seal to the pier better, and I could make it the desired thickness.
Heating your crawlspace would help a great deal--in fact if you keep it above freezing under there, then you might not even need foam--or at least only perimeter foam. I'm skeptical of your great stuff idea. Wouldn't it soak up water? Also, it would take a lot of it. If I was you, I'd try a 4'x4'x2" square of extruded polystyrene two layers deep ("Dow Blue" or equivalent) centered on each post. Bury it at least a foot, and bed it on a good layer of clean sand. That's just a seat of the pants guess.
If it's installed withn 6" of the earth or in it, it will need to be protected from termite and ants (they like to make tunnels in the stuff). A heavy plastic can be used if it can withstand soil chemicals (don't use poly).
I don't think there are a whole lot of termites in Northern Maine. Nor do I think carpenter ants are a problem if the foam is properly buried. The building department in my town requires the perimeter foam on a frost protected foundation to be covered with treated plywood or cement board, within 24" of the building. This is a recent addition to the code. There are hundreds of such foundations in my area without the board and they are functioning fine.
When getting and giving advice on a newsgroup, it is important to pay attention to where in the country the questions and answers are coming from. What is appropriate advice in northern Maine is not appropriate in southern Florida and vice versa.
Ontario). It's built on on-grade 24"x24" x2" slabs and using 2 concrete blocks to give me height. If I put a 4'x4' x 2" piece of dow under each support I wonder if that will give me the coverage I need.
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