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
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
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
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
http://www.countryplans.com/Downloads/shallowfound.pdf . Good luck--
you've got a tough one on your hands.
> Yes, buried foam can be used to prevent frost penetration. Here in
Here in the UK some areas have a problem with clay soil that moves as it
gets wet/dry (frost isn't a problem). We use foam to line the walls of
foundation trenches to stop the movement effecting the house. I guess frost
heave might be a more serious problem though.
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
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.
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,
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