ASHI HOME INSPECTOR - Austin, Cedar Park, Georgetown, Leander & Round Rock

In Central Texas we have many varieties of soils that the Austin home inspector should be aware of before he sets out for the home inspection.  Expansive soils can play havoc on a foundation regardless of the design.  This should be known before the potential buyer signs a contract on a new or existing home.  Existing homes most likely will show the evidence of foundation movement if the home has been built over ten years.  However, that is not the case with new homes.  The structure has not had time to settle thus the buyer cannot foresee what may await when he has lived in the house ten years.  By that time a structural engineer may be needed to assess the damages & recommend foundation repairs.  Don’t let this happen to you.  Do your home work ahead of time.  Talk to your home inspector in Austin, Texas & ask him for information on soil conditions in the area you want to buy.  If he does not know, then the home inspector should guide you to the Soil Conservation Service or a state agency that can help.

Expansive Soil   Â
Soil is an essential component in the construction and stability of a house that is often overlooked by homeowners and home buyers. Since the house is built on soil, structural damage to a house can occur if the soil expands, contracts or slides.

Expansive clay soils

Throughout the United States, particularly in Texas, California, Virginia and Colorado (though not exclusively in these locations), expansive or reactive clay soils are known to cause adverse effects on residential structures. Expansive soil expands and contracts due to changes in the moisture content of the soil, causing structural problems through differential movement of the structure. If the moisture content and or soil type differs at various locations under the foundation, localized or non-uniform movement may occur in the structure. This isolated movement of sections of the structure can cause damage to the foundation and framing, evidenced by cracking of the slab or foundation, cracking in the exterior or interior wall covering (indicating movement of the framing,) uneven floors and/or misaligned doors and windows. This type of movement is usually associated with slab on grade construction that is common in the previously mentioned regions of the country. However, this type of movement also occurs in structures with basements and crawlspaces. The following image of a moderately reactive soil sample illustrates its effect when moisture is introduced.

A second effect of expansive soils is additional horizontal pressure applied to foundation walls found in basements and crawlspaces. Increased moisture in the soils adjacent to the foundation wall will cause the soils to expand and increase the lateral pressure applied to the foundation wall. If the foundation wall does not have sufficient strength, minor cracking, bowing or movement of the wall may occur. Serious structural damage to, or failure of, the wall may also occur.

A third effect associated with claystone soil (a type of expansive soil) is the movement of soils on unstable slopes. Expansive claystone soil, found as a layer under a more rigid top layer of soils, become unstable as the moisture content increases, allowing the claystone and the top layers of soils to move. If the soil is located on a slope, the top layer of soil can creep (slow movement) down hill or even cause a landslide (sudden and dramatic movement). Consequently, a house with an inadequate foundation built on unstable slopes can be subject to creeping of the structure down slope, or to failure of the structure in a landslide.

Possible Solutions
Pre-construction solutions: Prior to building the structure, a soil test of the site should be performed to ensure the soils are stable or to determine the approximate effect the soils will have on the structure. This will assist in determining if the soils are capable of properly supporting the structure. In addition, information on the soils can ensure that the foundation is designed to withstand the effects of the existing soil conditions, and assist in the development of plans for long-term maintenance.

Post-construction solutions: For structures already in existence, several possible solutions to counter the effects of expansive soils are available. Common preventative solutions include proper soil maintenance such as maintaining a uniform and constant moisture level in the soil. This may involve introducing moisture into the soils continually and uniformly to prevent shrinking; and/or preventing excessive or isolated saturation of the soil through proper drainage and grading techniques that prevent swelling. For structures affected by expansive soils, further movement can be prevented by providing additional strength and support to the foundation. This may include various methods of underpinning (to prevent vertical movement and/or sliding) and/or reinforcing of the foundation walls (to withstand lateral pressure).

All of Central Texas is in a predominate area for expansive clay soils. These expansive soils act like a sponge. As they absorb water they swell and as they lose water they shrink. Soils tend to dry out (and shrink) during the summer and to absorb water (and swell) during the winter and spring. As this occurs your house and foundation will move up and down. So long as the foundation movement is not great enough to damage the house and/or foundation, it is not a problem. By keeping the moisture content of the soil under the foundation constant, foundation movement can often be minimized or even stopped. Please note that this is only a simple foundation preventive maintenance recommendation. Should you be concerned about the possibility of future movement or potential for movement or structural damage then a licensed structural engineer should be consulted for further evaluation and recommendations. The goal of a foundation watering program is to maintain a constant level of moisture in the soil under the house and foundation. The best way to water a foundation is to install a buried foundation watering system. If you do not want to go to the expense of installing a buried watering system, soaker hoses will provide you with many of the same benefits. The best way to use a soaker hose is to bury a soaker hose three inches deep, one foot from the edge of your foundation. Placing the hose a short distance from the foundation allows the water to soak into the soil evenly. The hose should not be placed against the foundation. When soil has dried and cracked, water can travel along the cracks for several feet in all directions. If the soil around your foundation is dried and cracked, then water placed next to the foundation will run through the cracks and accumulate at the bottom of the grade beam (the thick portion of the foundation that is under the exterior walls). In some cases, an accumulation of water in the soil at the base of a foundation can cause the soil to loose some of its load bearing capacity. If the soil loses enough load bearing capacity, the house will sink into the ground.

Obviously, it is necessary to water more during hot, dry weather and less during cold, damp weather. The amount of water required to keep a foundation stable during the summer can be surprisingly large. A single large tree can remove as much as 150 gallons of water, or almost 20 cubic feet of water, from the soil each day. Shrubs and other plants can also remove large quantities of water. During persistent hot dry weather, it may be necessary to water a foundation daily. Watering should supply enough water to keep the moisture content in the soil under the foundation constant. If the amount of water applied is only enough to keep the surface damp, the watering program will not work. Obviously, the homeowner is the only one who can weight the benefits of controlling foundation movement versus the increased size of the water bill.

Many concerns are considered during the home inspection. We have very expansive soils in Austin & surrounding cities that must be part of the home inspectors check list if he wants to protect his client from unwanted problems. Before you sign a home inspection contract or agreement you should ask the inspector to hire how he inspects foundations & feel confident of his knowledge. Repairs are more expensive than you would ever guess. Do you homework before you hire, you can thank me later. Read the article below to know more about foundations & how to protect yours.

A slab foundation is designed with concrete footings and /or underground piers and concrete floors. A pier and beam foundation consists of either wood or concrete piers that support beams above the ground. These beams support the floor joists and the floor joists supports the floor. A pier and beam foundation has a crawlspace under the home. It’s a good idea to inspect this area from time to time for plumbing leaks, flooding, rodent activity, and other potential problems.

Water should not stand next to the foundation for an extended period of time. The moisture in the soils will cause the foundation to heave in that area. The source of the water can be rain, or any number of possible plumbing leaks around the home. Repairing leaks is a must. Soil next to the foundation should be pitched in a way that will drain rainwater away from the home. It may be necessary to build the soils up next to the home with sandy loam or topsoil. Just remember, dirt should not extend higher than 2 inches below the bottom course of brick for a slab foundation or half way up the perimeter footing of a pier & beam foundation.

If clay soils next to the foundation becomes too dry, they will shrink, crack, and pull away from the perimeter of the foundation. The subsoil then loses its ability to support the foundation. Sooner or later the foundation will crack and settle into this void. These soil cracks can also admit water during heavy rains. The water will then wash the soil out from under the foundation. This will only make things worse. When the soil starts to separate from the foundation by up to an 1/8 of an inch, the soil needs water. Watering of the foundation should be uniform in order to minimize the possibility of exerting uneven pressure on the foundation. A sprinkler system, if installed and utilized properly, can provide the best protection.

The next best option is to place soaker hoses 12-18 inches away from the foundation. Water at least a few days a week, 10-15 minutes at a time, during the dry seasons of the year.

ASHI HOME INSPECTOR - Austin, Cedar Park, Georgetown, Leander & Round Rock

Homes with pier & beam foundations in Central Texas must be ventilated properly to increase air flow, reduce moisture accumulation, wood rot & mold growth.  Vapor barriers covering the ground in crawl spaces prevents rising moisture.  Wood piers should be elevated on concrete blocks.  Good drainage around all exterior of home must be observed.  Not observing these tips can prove to be costly to your home & your health.  Hire only an experience home inspector that will take special note of these items.Â

Inspecting foundations is a science. Neglecting foundations is foolish. When moving to Austin, Texas know that you are moving to expansive soils. Expansive soils contribute heavily to poor foundations and costly repairs.  Selecting the right foundation in a particular soil is critical.  Everyone buying a new or existing home should be familiar with the soil types in that region.  Contacting a seasoned structural engineer familiar with soil conditions can reduce you risk that might cost you later.  Your home inspector may not be familiar with the soil types to give you good council.Â