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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. Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman. What is Foundation Insulation's Role in Foundation Buckling
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?
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. Foundation Damage from Frost Generally Also Involves Water (Ice)
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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