North Texas is a great place to live. The mild climate and hospitable folks make for a salubrious atmosphere for people of all ages. But for the building of houses the area poses some considerable challenges:

Expansive Clay Soils

Foundations

Foundation Care and Maintenance

Watering

Drainage

Vegetation

Wood Destroying Insects

The Metroplex is located in northern part of the Texas Coastal Plain. The land is very flat, Blackland Prairie, characterized by dark, thick, plastic clay soils. Most of the soil structures in this area are better suited to crop production than to urban development.

The problem is in the shrink/swell potential. For the most part the area's soils tend to shrink when dry and swell when wet. This requires engineers to design structures that will remain stable while being supported by a constantly moving base. This movement is considerable in much of the area. Without going into great detail, let us just say that a stable soil has a PI (plasticity index) reading of 12-15. Most of the Metroplex soils weigh in at about 25-30. Some of the areas near the Irving, Las Colinas, Coppell area, for example, may measure as much as 70+.

Foundations (Back to top)

Now, that brings us to the foundations of our homes. There are basically two configurations of foundations in the North Texas area: slab on grade and pier and beam. The majority of houses built since the early 60's have been of the slab on grade type. Sometimes referred to as a "floating" slab, these are essentially large slabs of steel-reinforced concrete sitting atop the undulating soils of the region.

It is a credit to the engineers that most house foundations perform fairly well here. But, no matter how well a house foundation is engineered and constructed, if the homeowner does not properly maintain it, it will almost certainly develop problems over time.

Foundation Care and Maintenance (Back to top)

Preventing a problem is always more desirable than having to cure one. Certain maintenance procedures can help prevent or arrest foundation problems if initiated at the proper time and carried out diligently. The following are specific suggestions that help encourage foundation stability.

Watering (Back to top)

In dry periods, summer or winter, water the soil adjacent to the foundation to help maintain constant moisture. Proper watering is the key.

When cracks appear between the soil and foundation, the soil moisture is low and watering is in order. On the other hand, water should not be allowed to stand in pools against the foundation. Watering should be uniform and preferably should cover long areas at each setting, ideally 50 to 100 lin. ft. Too little moisture causes the soil to shrink and the foundation to settle. Too much water - an excessive moisture differential— can cause the soil to swell and heave the foundation. Along these lines never attempt to water the foundation with a root feeder or by placing a running garden hose adjacent to the beam. Sprinkler systems often create a sense of "false security" because the shrub heads, normally in close proximity to the perimeter beam, are set to spray away from the structure. The design can be altered to put water at the perimeter and thereby serve the purpose quite adequately. The use of a soaker hose is normally the best solution. From previous studies of infiltration and runoff it became evident that watering must be close to the foundation, within 6 to 18 inches, and excessive watering can be prevented by proper grade around the foundation.

A more sophisticated watering system is now available utilizing a subsurface weep hose with electric activated control valves and automatic moisture monitoring and control devices.  The multiple moisture control devices are situated to afford adequate soil moisture control automatically and evenly around the foundation perimeter. Reportedly, the moisture control can be set to maintain effective soil moisture variations to plus or minus 1%. Within this tolerance little, if any, differential foundation movement would be expected in even the clay soils.

Drainage (Back to top)

For the reasons noted above, it is important that the ground surface drain away from the foundation. Where grade improvement is required, the fill should be a low-clay or clay-free soil. The slope of the fill need not be exaggerated but merely sufficient to cause the water to flow outward from the structure. The surface of fill must be below the air vent for pier and beam foundations and below the brick ledge for slabs. Surface water, whether from rainfall or watering should never be allowed to collect and stand in areas adjacent to the foundation wall. Consistent with this, the installation of guttering and proper discharge of downspouts is quite important. Flower bed curbing and planter boxes should drain freely and preclude trapped water at the perimeter. In essence, any procedure that controls and extricates excess surface water is beneficial to foundation stability.

Vegetation (Back to top)

Certain trees, such as the weeping willow, grow extensive shallow root systems. These plants can cause foundation (and sewer) problems even if located some distance from the structure.

Many other plants and trees can cause foundation problems if planted too close to the foundation. Plants with large, shallow root systems can grow under the foundation and, as roots grow in diameter, produce an upheaval in the foundation beam. The FHA suggests that trees be planted no closer than their ultimate height; a safer distance should be at least 1.5 times the ultimate anticipated height.

Other plants remove water from the foundation soil (transpiration) causing a drying effect that in turn could produce foundation settlement.

Any extended differential in soil moisture can produce a corresponding movement in the foundation. If the differential movement is extensive, foundation failure will likely result. Of the two "categorized" type failures, settlement and upheaval, the latter is by far the more critical.

Even with proper care, foundation problems can develop; however, consideration and implementation of the foregoing procedures will afford a large measure of protection. It is possible that adherence to proper maintenance could eliminate perhaps 40% of all serious foundation problems.

Wood Destroying Insects (Back to top)

Subterranean termites cause hundreds of thousands to millions of dollars worth of damage in this area each year. But even though they are a fact of life in the Metroplex, they need not be a problem for you.

Contract with a local exterminating company to inspect your home for these pests and treat for them as required. Most companies will put you on a regular schedule for inspections as needed.

Keep all wood debris away from your house exterior. Resist the temptation to allow vines and shrubs to grow close to or on the surface of the exterior walls.

For More Information Contact:
Aaron's Home Inspections
Aaron D. Miller, CEI, CMI, CRI
7401 Vineyard Trail
Garland, TX 75044-2144
USA
Phone: 214-616-0112
Fax: 972-675-6371
info@aaronsinspections.com

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