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.
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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.
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:
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 on 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.
See WINTERIZE A BUILDING.
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.
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Below you will find questions and answers previously posted on this page at its page bottom reader comment box.
How can I evaluate damage from expansive clay soil
Our home is a late 1980's 2-story built on a concrete slab foundation where clay soil abounds.
During a very dry spell we moved our raised rack firewood, that was 1' away from wall, which revealed a 2'x6' wet soil area & what appears to be a 3' thin horizontal crack (maybe more than one or possibly "stair-stepped") holding ozed dirt & mold(?) growth along with a 2' area presenting a 1" bulging out of the concrete compared to the rest of the footing(?).
This is behind our kitchen & near a 3 1/2" pvc access pipe which is clean, clear, & passes no water.
Thinking plumbing issue w/footing & or slab compromised; research shows $$$ & not sure where to start: insurance, plumber (who cuts the concrete out?), struct. engineer, or concrete co.? - On 2020-10-26
by John
at HORIZONTAL FOUNDATION CRACKS
On 2020-10-26 by (mod) -
John
Thanks for an important and interesting question about investigating possible expansive clay soil damage that might affect a slab, foundation, and plumbing.
Thank you for the interesting question - it helps us realize where we need to work on making our text more clear or more complete. A competent onsite inspection by an expert usually finds additional clues that would permit a more accurate, complete, and authoritative answer than we can give by email alone. You will find additional depth and detail in the article series beginning on this page.
That said, I have these comments:Priorities for Evaluating Building Foundation Damage
There are several key concerns, and your question suggests we're of similar mind:
1. Structural condition, stability, safety
(not likely to be a major concern but worth ruling out) - see FOUNDATION DAMAGE SEVERITY https://inspectapedia.com/structure/Foundation_Damage_Assessment.php
for some detailed suggestions.
In general, IF you see horizontal cracking in a masonry-unit wall or foundation (block or brick, for example)
AND in particular if the wall is significantly bulged (say bulged in more than an inch)
OR if the wall is structural brick and cracked and bulged
See FOUNDATION BULGE or LEAN MEASUREMENTS
THEN there is risk of collapse that justifies an immediate evaluation by an experienced mason or if you hire an engineer, one who has specific experience and expertise in residential masonry construction.
Vertical cracks and non-bulged walls are usually less of an urgent concern as even if damage is significant and repair costly, the risk of a sudden precipitous collapse is considerably less.
See details at FOUNDATION DAMAGE SEVERITY
2. Electrical and fire safety:
if building movement has damaged or dislocated electrical wiring or a chimney or a heating fuel source piping then those conditions are dangerous and also merit prompt evaluation and repair.
3. Sanitation: i
f a sewage line is heaved it may fail to drain, or if it's broken it may release sewage: both potential sources of a sewage backup and health risks.
Let's start by your own visual inspection: you can probably see, without relying on precise measurements, whether or not the foundation wall is bulged or leaning or dislocated. If the damage is only to the slab itself but the supporting walls are un-touched then we can rest more-easily regarding priority item 1 and with a bit more visual inspection, item 2.
To evaluate item 3, when you say a pipe is clean, clear, passes no water I'm not sure what that means; but if you're not certain of the condition of drains in the area of heaving then you might hire a plumber with a sewer line camera to inspect the drain system for heaves or damage.
Please also be sure to
read EXPANSIVE CLAY SOIL DAMAGE to FOUNDATIONS where we wil re-post this conversation to invite pertinent comments from other readers.
Let me know what you see, think, find, are-told, or what questions remain.
Stay safe, and don't let this so distract you that you forget to vote.
I wonder if you've ever heard of a situation where the paved street creeps atop the clay soil? We have a situation where our soil is clay (Troy. MI). The street is pushing slowly against our driveway, which then pushes against our garage floor, and from there, the foundation.
We are on an inside corner in our subdivision.
A number of years ago, it cracked the top section of our poured concrete foundation and moved the section inward several inches.
When our builder repaired it, he told us that a nearby city (Brownstown, MI) also had a similar situation.
The driveway has been pushed approximately 2 inches toward our house, as evidenced by a visible difference between the control joint in the driveway and the edge of the sidewalk, which was originally in line with the control joint. We also had the builder cut a section from the back of the garage floor concrete to reduce the potential for contact with the foundation.
Additionally, we had sections cut at the sidewalk end of driveway and at the garage end, sufficient to replace the sections with pavers and still have room for sand to take up any movement. The additional room has reduced since we did this.
Our garage door track which is embedded in the concrete floor shows movement as well, and the framing has been moved to a point where the caulking has stretched past its limit. The movement is greater on one side than the other.
The city claims no knowledge and no responsibility for the movement of the street, despite having to replace most of the street a couple of years ago.
I am looking for other instances of the same issue to present to the city, since they said they "never heard of it", with an eye to (at a minimum) an abatement on our city tax commensurate with the reduction in value of the house (which they do not admit - especially since that is a different department). So far, I'm unable to identify the search terms that will locate such information.
Have you heard of this before? Do you have any instances that I could research and cite to the city? Can you help me find the correct search terms to find such instances?
I recently retired and my income has dropped significantly, leaving me in a place where I cannot afford to file a lawsuit against the city for damages based on their street engineering, and they refuse to consider that it might be their issue.
I would hate to see this happen to others, since homeowner's insurance doesn't cover the situation, and no one thinks about adding ground movement coverage to their insurance - likely because, as the city believes - it never happens.
Any assistance you could provide would be most appreciated.
Thank you, Anonymous, Troy Michigan, by private email 2019/10/07
Reply: street creep due to expansive clay soils
Yes Anon, expansive clay is, in some areas such as parts of Texas, a well-known source of pavement and roadway damage.
In addition, thermal expansion of some paved streets and sidewalks has been cited by contractors and engineers in hot climates such as Florida.
In the article above we include a reference to Dessouky (2012) as a PDF file that you might want to print and give to your doubters.
However you'd need an expert on-site examination and maybe some soil testing to make sure that the movement that concerns your property is from this effect since some of the distances involved may raise questions;
Also, if the street is moving and damaging your property I'd expect it to have had at least some effects on other drives and buildings along the same roadway; have you investigated and documented those effects?
Depending on the distances from the paved street to your building and the building and paving materials involved, even if neighboring homes also suffer foundation damage and even if that damage is due to expansive clay soil, it is possible that the damage is due to soil conditions beneath and surrounding the building itself.
Where the damage to the building is traced to forces exerted by the street paving itself we would expect to see continuous paving materials between the street and the building foundation walls or slabs, and we might see that some homes along a street suffer more damage than others, depending on the geometric relationship of the home's foundation to longer runs or wider expanses of street paving.
That is to say that the physical location of a home with respect to paved streets can cause some homes to suffer more than others.
For example a home whose driveway abuts the end of a street at a tee or cul-de-sac or whose drive abuts the outside radius of a curved roadway and whose own driveway or sidewalks provide a rigid connection between the home's foundation and the street may suffer more street creep damage than homes in other locations with respect to the same street in the same neighborhood.
Reader follow-up:
Yes, our neighbors on the inside curve have had a similar problem. When the builder came out to repair their house, after ours, he mentioned the same thing.
I have no problem with outside inspection, although I do have to clear that side of the basement for them to see the issue.
The repair to the foundation wall is obvious, as the stairs to the basement had to be moved to accommodate the repair.
The wall moved about 2 inches and was shored up and re-cemented. Since the crack was under the garage and behind the steps, there was no water leakage to deal with (thank Heaven), but the wall between the house and garage still sits unevenly on the top of the foundation and there is an uneven space between the stairs and the wall top to bottom.
Thank you for the information and the references. I will review them with my husband so that we can decide whether we need more information (measurements, outside inspection, etc.) before we approach the city again. Since I have recently retired, I finally have time to follow up on this again.
I so appreciate your help. May I contact you again if there are more questions once I’ve reviewed the reference material?
Reply:
Of course; the discussion and questions and research are helpful to us and perhaps also to other readers.
I don't think that inspection to confirm damage itself is critical since from your description the damage is quite apparent.
But onsite inspection of soil conditions around and under the home may be what's needed to support an argument that the expansive clay soil movement (as such soil expands and contracts in response to changes in moisture level) that has damaged the home's foundation is really traceable to the street as opposed to soil conditions immediately below and surrounding the home.
Photos of the site showing the street, home, damage, distances, surrounding control of roof runoff, description of any expansive clay soil damage management systems already in place, are examples of data that would be helpful.
What to do about Street Creep due to Thermal Expansion or Expansive Clay Soils
You will need advice from an onsite expert such as a geotechnincal engineer. However speaking rather generally, in addition to making any necessary repairs to the building structure or foundation, steps to protect the building from further thermal or expansive soil street movement or street creep might include cutting and installing expansion joints at right angles to the direction of pressure exerted by the street, at one or more locations.
Where expansive clay soil damage is due to local forces immediately around a building, steps to keep the soil at a more-constant moisture level, including sub-slab watering or de-watering systems, are commonly used.
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