Archive for the ‘Clay Soil’ Category

Why do I need to water my foundation during stage 3 or stage 4 water restrictions in Dallas Ft Worth? ?

Sunday, January 15th, 2012
Texas Lake bed near Dallas shows cracks in clay soil

Texas Lake bed near Dallas shows cracks in clay soil

During a period of drought, such as Texas experienced in 2011 and 2012, failure to properly water will lead to an uneven shrinkage of soil supporting the foundation, and is a major cause of foundation problems and foundation failure.

Maintaining adequate soil moisture is a key part of foundation maintenance in areas with clay soil.  Clay soil has a high index of plasticity, meaning that it is very sensitive to changes in moisture.  From its dry state, clay soil can expand up to 8 inches in the Dallas Fort Worth region.

City managers in Dallas and Fort Worth recognize the critical need to maintain adequate foundation moisture.  During stage 3 and stage 4 water restrictions, most cities still allow foundation watering for up to 2 hours per day.

While proper foundation watering can with patience be accomplished with a hand held hose, it is more practical to install a drip irrigation system or soaker hoses. A soaker hose system is adequate provided that the hose is properly spaced at a distance of 12-18 inches from the slab.  Never place a soaker hose in contact with a slab.

No matter what method is chosen for foundation watering, it is important to protect against overwatering.  Over watering is as disastrous as the lack of water. When clay soil becomes saturated (muddy), it loses the ability to support a foundation. The foundation will fail and crack.

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Why does soil consolidation cause a foundation problem?

Tuesday, October 19th, 2010

Soil consolidation is a leading cause of concrete slab foundation failure of houses in Dallas and Fort Worth, Texas. The soil lacks the strength to adequately support the foundation.

Improper preparation of clay soil can cause consolidation, which means that the clay soil becomes more dense with time.  Soil consolidation can continue for decades.

During building site preparation, the developer should assure that clay soil is at the correct moisture content to enable adequate compaction in thin layers using specialized heavy construction equipment.

If you suspect a foundation problem is caused by soil consolidation, you may want to hire an engineering firm to perform soil consolidation testing.  Site testing can run upwards of $2500.

If your house foundation has failed due to clay soil consolidation, you should consult a construction attorney as you may be able to take action against the site developer and or builder.

The weight of a house will facilitate soil consolidation. One way to mitigate future consolidation damage is by having steel underpinning/piers installed to take the load of the house off of the top soil in the areas where consolidation is taking place.  Sometimes it is necessary to pier the whole of the house  to fix foundation problems caused by soil consolidation.

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My house was built on an area of cut and fill. Is this why I have a foundation problem?

Tuesday, September 29th, 2009

Cut and fill is a major problem due to the expansive clay soils in the Dallas and Fort Worth areas of North Texas.

Why does improper fill cause a foundation problem?

Clay soil that has not been properly compacted will consolidate over time.. and we are talking about decades.  As the soil consolidates, it drops, and the foundation above it is no longer properly supported.  A foundation that is not properly supported will fail as it too will drop.

What is required to achieve a proper fill?

To properly “fill” a building site, the expansive clay soil must be compacted in no more than 4 inch layers, and be at the proper moisture level during compaction.   Proper moisture means that the clay soil can neither be too wet or too dry.

Why can a site cut cause a foundation problem?

When a site is cut down to a uniform height, expansive clay soil that was covered with over burden is now exposed to the water.   Newly cut soil can be characterized as dry and compact.   The compacted soil is good, but as the expansive clay hydrates (gains moisture), it will expand.  If a foundation is built over a newly cut area, it may heave as the soil hydrates.

Cut and Fill is the worst case scenario for a foundation.

For all the reasons explained above, a foundation straddling a cut and fill is a disaster waiting to happen.  The foundation tends to heave in the cut area, while sagging in the fill area.

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My foundation is heaving because it is on a cut area. Why do I have a foundation problem?

Tuesday, September 29th, 2009

During housing site development, some high areas of land are cut off, while the low areas are filled with the cut material.   This is called cut and fill.

Clay soil deep underground may be drier than the surface clay. When the clay is exposed to surface moisture after the cut, the soil hydrates.  The clay soil gains water content, and it expands.   The expansive soil swells, forcing the foundation upwards, and we say that the foundation has heaved.

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Why is expansive clay soil a problem for my foundation?

Tuesday, September 29th, 2009

Expansive clay soil that is correctly compacted and maintained at a proper and consistent moisture level is not a problem for a foundation.

There are four changes in clay soil which cause problems for our foundations:

  • Clay soil expands when it gets wet, causing the foundation to heave.
  • Clay soil contracts as it dries, removing foundation support, and causing the foundation to sag.
  • When clay soil is supersaturated with water, it turns to slippery mud, and the foundation sags.
  • Clay soil that has not been properly compacted will consolidate (become more compact and dense) with time.

If the moisture level in the clay soil under a part of a foundation increases, that area of the foundation will rise or heave.  If the moisture level  continues to rise, turning the clay to mud, the soil will lose its ability to support a foundation, and that area of the foundation will drop or slump.

When the moisture level in clay soil under a part of a foundation decreases, that area of the foundation will drop or slump.

Clay soil that has not been properly compacted during site preparation will consolidate over time due to the weight of the house.  If the consolidation of the soil does not occur evenly under the foundation, some parts will be less supported than others.

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