A Little About the soil conditions in Collin County

First of all, let me say right here, I'm not an engineer.  My experience with foundation movement comes from years of looking at engineering reports and talking to the engineers who wrote those reports.  I'm going to talk in generalities, but I can say with confidence what you read here is common knowledge.  First, a little about the different kinds of soil in the Dallas, Collin, and eastern Denton County area. 

Sandy Loam

If you've ever been to Aubrey or Pilot Point north of Dallas, you'll notice the dirt is reddish in color than you'll find further east in our area.  It's called "sandy loam".  That soil is the reason why there are so many large equestrian operations in that area.  When it rains there, the water just dissipates through the sandy loam soil.  You can walk around right afterwards without collecting mud on your boots.   

There are drawbacks to sandy loam as well as advantages.  People we know who live in Pilot Point and Aubrey tell us they are always living with gritty sand in their home, garage, cars, etc.  They just can't keep it out.  We don't share that problem on this side of the Metroplex, but we have to deal with the mud.  Sandy loam is not a problem soil for foundations.

Kalichi Rock

You might be surprised to find that some homes in Fairview, Lucas, and Parker have very little soil under them at all.  They are literally sitting right on top of "kalichi", a white rock you often see at the bottom of creek beds where the soil has been washed away.   Kalichi provides a wonderful footing for a foundation, but it can get expensive if you are digging a pool.  Dublin Creek Estates (Parker) and Oakwood Estates (Fairview) are two subdivisions that come to mind where the white rock is very close to the surface.  In fact, when Dublin Creek Estates was being developed I remember watching truckloads of dirt come in before the sod could be laid.  Give me a home resting on Kalichi near the surface and I'll pretty much guarantee the home and pool aren't going anywhere.

Black Gumbo

"Black Gumbo" is our problem soil and unfortunately, it's the most prevalent type of soil in Collin and Dallas County.  It can be very destructive to foundations if precautions aren't taken.   Many home buyers from other areas of the country have had little or no experience with this kind of soil and how to live with it.  Even many of those who are native to the area aren't fully aware of how damaging this kind of soil can be to a home foundation and how to protect their homes from it.

Black gumbo is a generic term for a highly elastic, clay based soil.    It's the clay that absorbs water in wet times, then loses it through evaporation.  That continual expanding and shrinking is what can wreak havoc on a foundation.  Farmers will tell you black gumbo is great for growing cotton, but when it comes to foundations, it can be a home wrecker. 

How do you know if your property has black gumbo soil?  Obviously, the first clue is if the soil is dark black.  But you'll know for sure the first time you walk on it after a rain.  The mud will stick to your shoes in big clumps.  The more you walk, the bigger your boots will get.  And until the land dries out, that's what you'll be living with.  Then, when the sun comes out, the soil dries out and large cracks will start to appear.  And these aren't always just little cracks.

Back in the 90's we suffered from a fairly lengthy drought, about two months without rain and day after day of hundred degree temperatures.  One day, I saw a large crack in our pasture and was curious how deep it was.  I dropped a 4 foot "tee-post" (one of those steel posts you see with barbed wire) into the crack and watched it disappear.  I wanted that post back, so I reached in to get it.  I had the entire length of my arm up to my shoulder into that crevasse and still could not touch the post it had fallen so deep.   Of course, when the rains finally came, the crack closed, and that post is still there to this day.

Why Black Gumbo is the Cause of So Many Foundation Problems

To put it in very simple terms, with black gumbo, when it rains, the clay in the soil absorbs the moisture and swells.  When the soil dries out, the clay loses its moisture and shrinks.  Although this is a continual process that occurs throughout the year without a major impact on the foundation, when we get into the extreme drought conditions or very rainy weather, the soil expands and contracts tremendously.  That's when your foundation is the most vulnerable.

All foundations settle a little after the homes have been built.  That might cause hairline cracks in a wall or ceiling, but it's

nothing to be concerned about.  That's why some builders ask their homebuyers to wait at least a year before they ask them to come out and touch up the hairline cracks.  You'll also often see hairline cracks in tile flooring within the first year or so after a home is built.  It might be bothersome to the new homeowner, but it doesn't mean the home wasn't built correctly.

But when the foundation shifts substantially as the result of massive soil movement, you can have major problems.  Doors might not close properly, window frames can shift and the windows lose their seals, sheetrock can tear, plumbing pipes can be sheared, exterior walls can exhibit major step cracking and if sever enough, it can even impact the functionality of the roof.  Once that happens, there's very little you can do except pay for an expensive foundation repair.

Important Signs to look for if your home is on Black Gumbo soil

When we go for weeks in hot weather without rain, just take it for granted the soil is drying out.  Unless you are really pouring the water onto your yard, you'll notice your grass pulling away significantly from the driveway or sidewalk.  That's a good sign the soil is drying out and shrinking.  It's time to check the soil around your foundation.  If you see a large gap developing between the concrete foundation and the soil, you need to get some moisture back into that area. 

Black gumbo soil can move horizontally, stretching and pulling apart, then moving together again.  Those forces are the reason I recommend concrete over asphalt on driveways.  Your asphalt driveway will look great for a year or so, but eventually the cracks will open.  Traffic will start breaking down those areas and the asphalt will start to crumble.  Concrete costs at least three times more than asphalt, but you only have to do it once for driveways. 

The black gumbo soil can also move vertically as well as horizontally.  "Heaving" is the term used when soil expands and starts to lift a structure.  That kind of movement is most damaging to homes.  Although some homeowners believe the concrete piers they paid extra for beneath their home are all that's needed to protect them from foundation damage, it's not quite that simple.  Heaving soil can actually lift the home off the piers causing major structural damage.    

So What's The Answer?

The good news is, there's a simple solution to protecting your foundation.  All it takes is keeping the soil around the foundation at a fairly consistent moisture level throughout the year ... especially during the dry spells.  If you have a sprinkler system in the beds around the perimeter of your home, you are going to be OK as long as you use it.  It's tempting to back off on watering when money gets tight, but you can easily save yourself from a major foundation repair just by concentrating on the soil around the foundation.  When we're in a drought situation run it several times a week and that should be plenty to keep the soil moisture conditioned.

If you don't have a sprinkler system around the perimeter of your home, place a soaker hose around the entire foundation.  You can connect it to your hose bib with a battery timer and run it every three days or so during drought periods.  But don't lay the soaker hose right next to the foundation.  If you do, the water will just run down the void between the foundation and the soil and you have accomplished very little.  Lay it at a couple of feet away from the concrete and let it soak the area slowly.

Finally, if you have beds around your foundation, put a thick layer of mulch over the top.  That not only keeps the weeds down, it also helps prevent the dramatic loss of moisture through evaporation.  But never allow the mulch to extend past the brick line or you're inviting trouble from insects.

Follow these steps and I'll bet you'll never have to make that call to a foundation company for a repair. 

Tom Grisak Estate Homes Realtors, Inc - Texas License # 0329533

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