Expansive Clay Soil Damage to Foundations
The Main Causes of Buckled Foundation Damage in Wet, Freezing Climates with Clay Soils
FOUNDATION FAILURES in CLAY SOIL - CONTENTS: Main Cause of Foundation Failures in Clay Soils. Roles of water, frost, clay soils, and insulation in foundation damage cases Where and with what material can we insulate building foundation walls?How Avoid Foundation Cave-Ins How do we prevent foundation damage - key steps. Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices
POST a QUESTION or READ FAQs about the causes of buckled building foundations for structures built in wet freezing climates and or on clay soils
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Expansive clay soil damage to building foundations or slabs:
Role of frost, freezing, & clay or wet soils in foundation heaves, cracks, damage: this article explains the main causes of foundation cracks, buckling, or collapse in areas of freezing weather, clay soils, or wet soils.
We provide suggestions for avoiding foundation damage or collapse and we discuss the proper foundation insulation locations and materials for use in problem areas. Photo (above) shows a new foundation constructed below a New York home after a catastrophic foundation collapse caused by wet soils.
What is the Main Cause of Foundation Failures in Expansive Clay Soils?
The USGS defines "expansive soils" as
Types of soil that shrink or swell as the moisture content decreases or increases. Structures built on these soils may experience shifting, cracking, and breaking damage as soils shrink and subside or expand.
The following includes text adapted from Solar Age Magazine, Steven Bliss: Most foundation failures in clay soil have nothing to do with freezing. The culprit is more often the expansion of the soil when it absorbs water.
In Fargo, said housing engineer Lambert Vogel, when the soil dries out and shrinks, it can pull away from the foundation as much as two inches to a depth of three feet or more.
Either the wind or the homeowner is likely to fill this crack with loose soil. When the clay soil gets wet again and expands, crack goes the wall - if it is weak.
In some areas of expansive clay soils such as portions of Colorado, builders install a soil watering system below the building's foundation and slab in order to prevent this clay soil shrinkage during dry weather.
Watch out: other more varigated concrete crack patterns (shown below) may be ascribed to FOUNDATION DAMAGE by MATERIAL or INCLUSIONS producing soil heaving, unstable soils, or crack patterns in concrete caused by inclusion of iron sulfide (pyrrhotite) particles in the concrete mix itself.
Recommendations to Avoid Foundation Wall Cave-Ins in Cold Climates
Vary rarely do foundation walls cave in from insulation, except possibly in Duluth, Minnesota, where all the conditions are ripe for foundation failure: lots of rainfall, clay soils, very cold winters, and building practices that often do not include foundation drainage to assure that soils close to the building foundation are not water-saturated.
But you can prevent all frost-related foundation damage problems by following standard good building practices:
Provide positive site drainage - do not direct surface or roof water spillage against or close to the building foundation
Use granular backfill or gravel around foundation walls, including footing drains that carry water to daylight well away from the building
Build foundation walls strong enough to withstand unavoidable intermittent pressures and loads exerted by water or ice.
If your foundation insulation is to be installed on the outside of the wall, use a material such as Styrofoam that will not lose its insulating value when exposed to moisture or water.
If your foundation insulation is to be installed on the inside of the foundation wall, we still prefer using insulating foam board products such as high R-value urethane foam boards rather than fiberglass insulation. That's because fiberglass against or close to a below-ground-level building foundation is exposed to moisture from both the building interior as well as from the building exterior.
Moist or wet fiberglass insulation not only loses its insulating value, but it can become a problematic mold reservoir in the building.
See FIBERGLASS INSULATION MOLD.
Given basically sound foundation and site work, it is acceptable to insulate a building foundation inside (giving up the thermal mass benefits to the building) or outside, and to install foundation wall insulation half-way, full-height, or flared-out - anywhere in the continental United States.
In foundation insulation retrofits in very cold climates, life is not so simple. What if you have an un reinforced concrete block foundation, a frost-susceptible soil (clay or silt), and poor site drainage? Then we would be reluctant to install any foundation insulation without first correcting the site - at the very least by conducting surface water and roof spillage well away from the building foundation.
Where the integrity of the foundation wall is in doubt, there are compromise solutions. We might install half-height insulation on the inside of the foundation wall, or half-height insulation n the outside of the foundation wall with the addition of at 2- to 4-foot flare.
But don't expect good thermal performance with half-height interior foundation insulation on an open-core concrete block foundation wall. Convection in the concrete block cores will carry heat right past the insulation.
Also consider the wintertime temperatures in the basement or crawl space. If the building owners have insulated the basement or crawl space ceiling, and are heating with a woodstove upstairs rather than a furnace or boiler in the basement, the basement walls, not to mention the water pipes could get very cold.
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.
Useful Research on Expansive Soil Damage Assessment
Al-Rawas, Amer Ali, and Mattheus FA Goosen, eds. Expansive soils: recent advances in characterization and treatment. Taylor & Francis, 2006.
FOUNDATION DAMAGE by MATERIAL or INCLUSIONS - heaving damage to foundation walls & cracking foundations or slabs due to Iron sulfide mineral (pyrrhotite) inclusions in concrete or due to building on Iron sulfide mineral (pyrrhotite) shale.
Hamberg, D. J., and J. D. Nelson. "Prediction of floor slab heave." In Fifth International Conference on Expansive Soils 1984: Preprints of Papers, p. 137. Institution of Engineers, Australia, 1984.
Ito, Maki, and Shahid Azam. "Determination of swelling and shrinkage properties of undisturbed expansive soils." Geotechnical and Geological Engineering 28, no. 4 (2010): 413-422. also referring to Proceedings, 4th international conference on expansive soils, Denver, Colorado, USA.
Jones, Lee D., and Ian Jefferson. Expansive soils. ICE Publishing, 2012.
Miller, Debora J. Expansive soils: problems and practice in foundation and pavement engineering. John Wiley & Sons, 1997.
Noe, David C. "Heaving‐Bedrock Hazards, Mitigation, and Land‐Use Policy: Front Range Piedmont, Colorado." Environmental Geosciences 4, no. 2 (1997): 48-57.
Gill, J. D., M. W. West, D. C. Noe, H. W. Olsen, and D. K. McCarty. "Geologic control of severe expansive clay damage to a subdivision in the Pierre Shale, Southwest Denver Metropolitan area, Colorado." Clays and clay minerals 44, no. 4 (1996): 530-539.
Abstract: Shortly after construction of a subdivision in the southwest Denver metropolitan area in 1986, a portion of the subdivision built directly on steeply-dipping strata of the Pierre Shale began experiencing damaging differential movements, causing house foundations to fail and pavements to warp and crack. This formation is a Late Cretaceous marine clay-shale composed predominantly of fluvial mixed-layer illite/smectite and quartz. During deposition of the shale, periodic and explosive volcanism generated thin beds of bentonite, consisting initially of volcanic ash and subsequently altered to nearly pure smectite.
Some of these bentonite beds were exposed in a trench adjacent to the subdivision and perpendicular to the strike of the steeply-dipping strata. The thickest bentonite beds correlated well with linear heave features that these beds parallel the bedrock strike throughout the subdivision were mapped via severely deformed pavements. Mineralogical data show the bentonite bed that correlates with the worst damage within the subdivision consists of about 62% smectite by weight with mixed-layer illite/smectite expandability of 92%. By comparison, a sample of the typical silty claystone, which is fluvial mixed-layer illite/smectite mixed with detrital quartz from the adjacent strata, had about 23% smectite by weight with 70% to 90% illite/smectite expandability.
Geotechnical tests for swell potential show that samples of 2 bentonite beds swelled 39% to 43% compared to 2% to 8% for samples of the typical silty claystone. It is proposed that differential swell resulting from stratigraphically-controlled differences in clay mineralogy and grain-size is the primary factor controlling extreme damage for this geologic setting.
Wells, R.R., S.N. Prasad, and M.J.M Romkens, 2001a. Cracking modes of an expansive Mississippi
Delta soil. In Mississippi Delta management systems evaluation areas project, 1995-99,
Mississippi Agricultural and Forestry Experiment Station Information Bulletin 377.
Abstract: Modes of cracking in expansive soils of the
Mississippi delta and their impact on infiltration were
examined. Preliminary laboratory infiltration studies
suggested an evolutionary pattern of the crack
network. Subsequent studies were conducted to
investigate the primary modes of crack formation and
their impact on infiltration. Of particular importance
in the evolution of the crack morphology, the role of
the seal and development of stress within the
substrate is discussed. Understanding the
developmental aspects of cracked soils permits
further development of infiltration relationships that
are used to determine the transport capabilities of
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Solar Age Magazine was the official publication of the American Solar Energy Society. The contemporary solar energy magazine associated with the Society is Solar Today. "Established in 1954, the nonprofit American Solar Energy Society (ASES) is the nation's leading association of solar professionals & advocates. Our mission is to inspire an era of energy innovation and speed the transition to a sustainable energy economy. We advance education, research and policy. Leading for more than 50 years.
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Steve Bliss's Building Advisor at buildingadvisor.com helps homeowners & contractors plan & complete successful building & remodeling projects: buying land, site work, building design, cost estimating, materials & components, & project management through complete construction. Email: email@example.com
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com
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