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frost heaving: patio and garage

We just moved to Wisconsin this past summer and we've had some epic weather, with record-breaking snowfall and torrential rains.

Our house was built in 1955, patio in 1978. The several feet of snow covering our patio since December have just begun melting and we are now seeing that sections of the concrete slab are cracked and heaving up, one chunk by a couple inches. It literally looks like a minor earthquake has hit our backyard, with big bulges sticking up. It's affecting the garage as well - we can no longer open the side door on the garage, it jams in the frame. Our concrete driveway has also taken a major hit. Things are a little awry in the house too, although I don't see any cracks in the basement (most of the floor is covered up), a few doors are mysteriously not fitting into their frames anymore, and others have loosened up.

This being my first experience in a cold climate like this, is this normal?? Does the soil settle back down again once the ground has fully thawed? What do you do to prevent this, and is it really expensive to get fixed? I can't believe this house has stood here 50 years and the patio 30 years, and we move here and the patio and foundations all get destroyed in 6 months!

Re: frost heaving: patio and garage

Talk to an attorney familiar with real estate law to see if you can file a claim against the seller, since the purchase was made recently.

It's hard to believe the seller didn't know about the condition & had a duty to reveal any such condition before the sale was finalized.

Frost heave is somewhat of a common event in northern climes like Wisconsin, and varies from winter to winter, depending on the severity of the weather, & the amount of fall rain, which can soak the subsoil & create high water table for the winter frosts.

Call your city hall building dept. & ask what the FROST LINE is for your locality.

The FROST LINE is the amount of feet the winter frost will penetrate & freeze the ground during the coldest winter days.

For Wisconsin, it may be 3-4 feet or more.

Foundation contractors & those who lay water supply pipes have to GET BELOW the frost line to prevent building heave or frozen water pipes.

This works fine for a foundation set below the frost line or water pipe---it's the patio, driveway, & sidewalk slabs that are only a few inches thick, have a wide open area that the sub-freezing cold can easily penetrate, & easily freeze the water under it; the water turns to ice & pushes up & heaves & cracks the concrete slab.

The distorted slab or concrete walk will almost always go back to its normal position when the ground below thaws---that's a good thing.

But the BAD thing is that it indicates that the patio or garage slab was improperly installed, probably on soil that holds a lot of water (silt, clay, fine particle hardpan), and NO drainpipe was installed to carry the water away so freezing wouldn't cause a heave.

Standard practice when poor non-draining soil is encountered is to excavate 1 foot of the non-draining soil & install 6" to 1 foot of crushed stone to improve the drainage & would also control the heave; perforated 4" drainpipe is installed to carry away the water to a drywell; 5/8" steel rebar or steel wire screen mesh is installed in the fresh concrete to minimize cracks and heaving & tie the entire slab together.

There is also 3" thick extruded polystyrene styrofoam 4 X 8 sheets that are often laid before the crushed stone is installed; this prevents the bitter cold air from penetrating down to freeze the subsoil.

Most or all of these measures, no doubt, should have been, but were not done in your case.

Aside from ripping up the slabs & starting over, -----hope that it was just a bad year for excessive freezing & frost heave & won't happen regularly in the future.

Sometimes palliative measures such as driveway caulking & keeping as much water as possible out of the cracks will help to minimize future winter heaves; a length of rope or some pink fiberglass insulation is stuffed into the crack before the caulking is installed.

There is a product called Thompson's water seal available at HD/Lowe's that can be brushed on the patio or driveway with a push broom in the fall that often helps.

Is it something you can live with, or are you ready to remove part or all of the slab to redo the patio/driveway?


Re: frost heaving: patio and garage

This being my first experience in a cold climate like this, is this normal??

To a degree ...yes it is normal .... some items like concrete patios , driveways , sidewalks and heck you might even notice some of the roads around you are slightly heaved with some more than others.

Simply what happens is the moisture in the ground freezes .... and when water freezes it's size expands. When they talk about the frost in the ground that generally what's being referred to .... how far down the moisture in the ground is frozen.
Now ... if the fall season was very wet and lots of water saturating the soil then when the cold temps come all this water will freeze with more aggression .... because of the excess moisture. Think of putting water into a plastic container and freezing it solid .... the ice will expand quite a bit and actually break open that container.


Does the soil settle back down again once the ground has fully thawed?

It will though it may not return to it's exact place before freezing.


What do you do to prevent this, and is it really expensive to get fixed?

Short of moving to a warm climate ( sorry bad joke :D ) not much as far as prevention. Although one think for prevention on things like the driveway and sidewalks or the patio is .... if there are cracks seal them to not allow water to penetrate down through these cracks mainly before the cold season. This will help preventing further cracking from the water sitting inside this area when it would freeze and expand.... further damaging things.

As for getting fixed .... would depend on what things .

As for the foundation of the home there can be things done to help.
In different areas the ground frost will penetrate to a certain depth. In this area for example .... on average the ground frost can penetrate to a depth of 6 feet ( frost line ) and in some cases down to 8 feet in certain areas.

The basements have been dug so the foundation footings are at a level further than the expected frost line to prevent frost heaves.
There can be an issue with a thing called ad-freeze which is a condition where the foundation walls absorb moisture and when the frost in the ground freezes to the foundation and heaves this will move the foundation .... causing some shifting of the house or cracks in the foundation.
A method to combat this issue is to have the exterior foundation walls coated with a waterproof material and have a membrane installed as well. The membrane not only helps with waterproofing but also provides an isolation buffer between the ground freezing to the foundation.

This may not have answered all your questions but I hope it helps.:)

Re: frost heaving: patio and garage

Sorry for the duplicating some of JacktheShack's informative post .... I'm kind of slow in the 2 finger typing department.:o

Re: frost heaving: patio and garage

Thanks for all the replies. I think taking any legal action will be tough. The sellers did disclose cracks in the driveway, and it's possible that the water/frost levels in the soil this year were worse than any year since the patio and garage were built (over 100" of snow this winter, prior record of 76" in '78-79; wettest August ever). The patio didn't look anything like this when we purchased, and there appear to be numerous new cracks.

We'll see how well it settles back. The garage door is going to need to be replaced or modified to fit the frame. We may need to replace the driveway and patio before moving, but that will be a ways off. We'll be mindful of the 'frost line' and proper drainage when we do!

Re: frost heaving: patio and garage

It's hard to predict what dear old mother nautre will do.

Another thing I didn't mention ...... in areas were there are frost heaves the use of paving stones is popular. Since the ground may heave it becomes a simple method to repair things like patios , sidewalks , and driveways.

Heres an example : http://www.hometime.com/Howto/projects/patios/patios_1.htm

Hope this helps. :)

Re: frost heaving: patio and garage

I am a fellow Wisconsinite and have been told that the frost line in the southeast part of the state is 48". We have not experienced the destruction described earlier, although we have noticed a foundation wall crack that appeared sealed 2 years ago when we bought the house has now opened back up. Perhaps due to the record snowfall and the tremendous moisture content in the ground. Something we will have to address soon. Good luck.

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