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Do foundation cracks occur due to foundation insulation? This article discusses the causes of foundation cracks, buckling, or collapse in areas of freezing weather, clay soils, or wet soils. We discuss the role of building insulation in foundation damage, the question of whether or not foundation insulation is the root cause of foundation damage or collapse in very cold climates, and the role that water and frost play in foundation damage. We include suggestions to avoid foundation collapses.
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In this article series we include solar energy, solar heating, solar hot water, and related building energy efficiency improvement articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss. Photo (above) shows a badly buckled concrete foundation. Notice the water stains starting at the top of the wall in the right side of the photo?
Readers who need to diagnose the cause and decide on the cure for foundation damage should start at FOUNDATION CRACKS & DAMAGE GUIDE. Readers should also see BASEMENT HEAT LOSS for a discussion of basement and foundation insulation. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
The text below includes and expands upon the original material (the two PDF files above); it paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.
Readers should see BASEMENT HEAT LOSS for a detailed discussion of insulating building foundations. See POLYSTYRENE FOAM INSULATION for a guide to using this material in below-grade foundation insulation applications. See TERMITE SHIELDS vs TERMITICIDE for a discussion of avoiding insect damage when foam insulating board is used below or at ground level. See WET BASEMENT PREVENTION for other exterior treatments of building foundation walls to combine foundation insulation with basement waterproofing membranes and drainage systems.
Buckled Foundations: Is Insulation Guilty?
Every now and then we hear a story about insulation causing a foundation wall to crack. But until I received a letter from Minnesota engineer Paul Shea, I had never had one of these stories verified. Shea wrote that "Buckling of foundations as a result of adding insulation is well known in Duluth, Minnesota. I personally audited three houses in Duluth that performed OK until insulation was installed."
Our photo (left) of above-ground building perimeter & foundation insulation is from a home we observed in Maine - Ed.
When I called Shea, he had four cases to report, two of which took place in "vegetable rooms" - small basement alcoves for storing product - that had been insulated in otherwise uninsulated basements. In each case, said Shea, the walls buckled after they had been insulated on the building interior side, either with fiberglass or polystyrene insulation.
The failed foundation walls faced uphill sides of sloped sites, which acted as catch basins for rain and meltwater. As far as he knows, all of the walls were of un reinforced concrete block. The soil in the area, he said, is very heavy clay. The climate is very cold (10,000 degree days) and wet. Frost penetrates to five feet and deeper in Duluth, Minnesota. [DJF Note: we have seen similar foundation collapses in New York State where the combination of freezing with very wet soils pushed in the masonry block foundation wall. In similar structures where there is not a problem of wet soils (from improper surface or roof runoff disposal) these problems are rarely seen.]
I Tracked down another foundation damage case in the area and spoke with the owner, who, incidentally, sells masonry supplies for a living. He had insulated two adjacent foundation walls with extruded polystyrene, planning to finish the other two walls later. That winter, one wall cracked and the other burst, pushing up in six inches at one joint. The wall that cracked had a concrete patio next to it. The wall that gave way abutted the driveway. The house, said the owner, had been built around 1920. It cost him $3600 to repair the two foundation walls. At the time the basement burst, he said, the room was cold - it had no heating boiler or furnace - just a small, rarely-used space heater.
In the Duluth area, said the owner, many builders won't insulate foundations on the building interior. Even when they put insulation on the foundation exterior, he said, some hold it a foot short of the footing - to let household heat bleed into the soil to moderate the freezing. Minnesota Power Co. energy auditor Roger Freeman recommends that the basement insulation stop two feet below grade and then flare out if desired (see the "Scandinavian Flared Foundation Insulation Option" described at BASEMENT HEAT LOSS). Some Minnesota contractors refuse (in the 1980's) to install basement insulation altogether - though this cannot be an energy efficient building design.
Across the state of Minnesota, in Fargo, North Dakota, they don't seem to have this problem. Soils Engineer Duane Heley, of Midwest Testing, in Fargo, said he has seen many basements damaged by expansive clay soils, but none he could attribute to frost problems. On the other hand, he has seen frozen soil drag up and displace exterior foundation insulation (frost lensing is discussed at VERTICAL MOVEMENT IN FOUNDATIONS). For that reason, he recommends placing foundation insulation on the building interior, where Mother Nature will not push it around.
In 11,000-degree-day Saskatchewan, they don't seem to have any problems with basement insulation according to building researcher Bob Dumont. The reason may be that Saskatchewan has only 15 inches of precipitation annually, compared with Duluth's 28 inches of rainfall, most of which drops in the summer and fall - saturating clay soils there. Other cold-climate soils engineers I contacted around the country concurred that they had never seen frost action cause structural damage to residential foundations.
DJF Note: we have seen foundation collapses in New York State where the combination of freezing with very wet soils pushed in the masonry block foundation wall. In similar structures where there is not a problem of wet soils (from improper surface or roof runoff disposal) these problems are rarely seen.
Solving the site's water problems seems critical for builders and owners who want both energy efficient buildings (incorporating at least some foundation insulation) and also to avoid frost damage to the foundation caused by the combination of water and freezing conditions.
In the Hudson Valley of New York State when we see horizontal cracks in the upper third of a concrete block foundation wall that is mostly below grade (photograph at left), we associate that damage with water and frost - the frost line is about three feet down in the Hudson Valley.
When we see cracks and movement low on the foundation wall, near the floor, we associate that damage with earth pressure, possibly exacerbated by the extra weight of water and vehicles, but not with frost. More about diagnosing horizontal foundation cracks and movement is at HORIZONTAL MOVEMENT IN FOUNDATIONS. BUCKLED FOUNDATIONS due to INSULATION?
Here we include solar energy, solar heating, solar hot water, and related building energy efficiency improvement articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.
"Buckled Foundations: Is Insulation Guilty?" - links to the original article in PDF form immediately below were preceded by an expanded/updated online version of this article. This article by Steven Bliss reviews four case reports addressing foundation damage in which the building insulation may have played a role.
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Frequently Asked Questions (FAQs)
I was watching a show several years ago that showed a flat insulated board that was laid on an angle away from the foundation to prevent water/ice forming around the foundations in Vermont. I have been wondering ever since what that material was and if it worked. It was placed at the frost line on a downward slope. Any ideas? - M.M. 8/26/20134
1. I have some experience with trying to get water away from buildings and with using insulation to avoid several problems:
- frost push, foundation cracking, movement
- frost lensing, foundation is lifted by heaving soils (Ice Lenses, Frost Heaves vs. Frozen Soil Pressure) - foundation leakage
Along with Steve Bliss we've published some relevant notes on an old debate about whether or not foundation insulation might even cause rather than avoid foundation damage - see BUCKLED FOUNDATIONS due to INSULATION? at http://inspectapedia.com/Energy/Buckled_Foundation_Insulation.htm
In my experience & OPINION, using solid closed cell foam insulation alone to try to get water away from buildings is ineffective or not cost effective or both; Considering that most foundations are built in a larger-sized excavated hole, backfill around the foundation is less firmly packed than other virgin soil at the same site. A result is that even if soil slopes away from the foundation, water spilling close to it or running close to it from in-slope grade tends to soak down through the soil where there is risk of frost and leak damage to the structure.
A sloped foam insulating pad is not water-tight unless abutting seams are sealed and even then may be too narrow a drain-pad around the building unless extended far enough away to deliver water to the surface at a location where it continues to drain away from the structure, or to deliver water to a buried drainage system well away from the building and continuing to daylight or to a storm drain. So I'm doubtful that a foam insulation apron alone keeps water from running beneath itself and thus towards the structure.
What's left then: well the foam may slow or reduce the freezing of soils close to the building, while still admitting water.
2. I have not inspected a structure with a foam apron at or close to grade, sloping away, that prevented frost or water damage;
3. I have inspected, and also helped design and install geotextile installations that waterproofed around a building foundation; we used this approach at a metal-roofed converted barn home in Newbugh NY because the owner simply could not keep gutters on the building. Key was getting roof spillage away from the foundation by a combination of a buried geotextile combination of plastic and fabric matting that sloped at least 10 ft. from the structure, in some locations more, and terminating where water was then drained off of the property; we backfilled and seeded or sodded over the geotextile installation, maintaining the desired drainage contour; close to the building walls we installed a band of gravel to reduce rain splash-up onto the building walls along the roof drip-line.
You will want to see BASEMENT HEAT LOSS for a detailed discussion of insulating building foundations. See POLYSTYRENE FOAM INSULATION for a guide to using this material in below-grade foundation insulation applications. See TERMITE SHIELDS vs TERMITICIDE for a discussion of avoiding insect damage when foam insulating board is used below or at ground level. See WET BASEMENT PREVENTION for other exterior treatments of building foundation walls to combine foundation insulation with basement waterproofing membranes and drainage systems
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