Texas Inspector License #5229
Inspection Services in the Greater Houston Area
Office 281-794-9102
Inspectors Mobile 832-671-2258
Foundations
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During the inspection the foundation will be checked with a laser level to help determine how it is performing and also for the following: -Identify the type of foundation and determine if the foundation is performing properly. -Inspect the foundation, related structural components and slab surface where possible. -Inspect the crawl space area of pier and beam construction to determine the general condition of the foundations structural components. -Inspect the area on pier and beam homes for proper crawl space ventilation. -Observe the site for conditions which may be adversely affecting the foundations performance, such as improper grading and drainage, plumbing leaks and or ponding. HOUSTON AREA SLAB FOUNDATION INFORMATION Many foundation movement problems in areas with expansive clay based soils are moisture related. Active clay soils will shrink when dry and swell when wet. Foundation movement can result when wet expanding soils cause upheaval and dry soils cause settlement. Minimizing the risks of foundation movement caused by these geological conditions requires you to assist in maintaining uniform consistent moisture levels in the soil surrounding the foundation. Foundation problems can result without proper maintenance on the homeowner’s part. Maintenance can be accomplished by doing three things. 1.Provide good drainage away from the foundation. 2.Water the soils surrounding the foundation on an as needed basis. 3.Be aware of the potential for adverse affects caused by trees and shrubbery. Perhaps the most important part of foundation maintenance is providing proper drainage and soil level heights around the home. Water should always drain away from the home and ponding conditions near the exterior grade beam should be avoided. Recommendations can vary, but generally it is wise to avoid letting water pond within 6 feet of the grade beam. Soil height below the top of the slab or brick ledge should generally be 4 to 6 inches. Again, this specification can vary from house to house and the particulars of each foundation will determine the best soil height. Soils that are above the top of the foundation or above the brick veneer are too high and are conducive to water and insect entry into the home. Soils that are too low can promote quicker dehydration of underlying supporting soils. Generally the soil should be 4 to 6 inches below the top of the slab. What is a “good slope” for adequate drainage? Various guidelines can be found in Code books, Government specifications or Engineering publications and some minor variations between these groups may exist. However, 6 inches of slope for the first 10 feet away from the home should be provided around the foundation. This slope should drain off the property site. Contouring the home site may require construction of swales; that is, wide shallow sloped depressions constructed to channel water flow. Again specific recommendations will vary from site to site. Areas, which are difficult to properly grade, may require special provisions. For example, an interceptor drain consisting of a solid pipe placed underground and routed to a proper discharge point may be required. In cases where subsurface water flow must be controlled, specially designed French drains are used. Sometimes water cannot be discharged by means of gravity flow and in such special situations, pumps are required. Areas of slow drainage or soil erosion resulting from runoff can often be improved by using gutters. Generally, if good drainage exists and erosion is not a problem then gutters are not necessary. However, when conditions warrant, gutters can reduce excessive water accumulation. It is important that gutter downspouts direct water away from the foundation and that they not allow water to simply collect at the downspout discharge point. If necessary, use extended downspouts to direct and control water flow. In some cases, connecting the gutters to underground drains may be required. Gutter downspouts discharge erosion can be controlled with properly placed splash blocks. Garden edging and fences can sometimes cause problems because they prevent water flow. Pay attention to these conditions and provide outlets or drains where needed. All of the aforementioned efforts contribute to controlling excessive moisture. Remember that excessive moisture makes clay based soils expand, swell, and uplift. Once soils around the home are contoured and shaped to provide good drainage, then preventing excessive dehydration becomes the goal. Soil dehydration results from lack of rain, hot outdoor temperatures and surrounding plant life. You can assist Mother Nature by replenishing water in the soil on an “as needed” basis. This is best accomplished by watering slowly, consistently, and uniformly around the perimeter of the home when conditions warrant. Special cases can affect final watering decisions, for example: Water more frequently in the hot dry months of summer than in the cooler months of winter The south and west sides of the home are more likely to experience hot sunny exposure and thus may require more water than the shady north and east sides. If the neighbors lot drains toward your site, then that side of the house may require less watering. Methods of applying water vary from the use of soaker hoses to automatic sprinkler systems. Automatic sprinklers are certainly more convenient but soaker hoses can do just as good a job. There are some new innovative watering systems being tried but until more conclusive performance history of these systems is available, we must withhold our comment. How much water and when to water is the next consideration. Just setting the automatic control and forgetting it is probably not going to work. Perhaps the most important thing to remember is that clay based soils absorbs water slowly and obtaining ideal moisture content takes time. Applying a lot of water over a short period of time will result in wasted runoff or in dry conditions possible upheaval. Slow regular watering periods are needed in order to allow moisture to penetrate the deeper soil particles. Generally, about 1 to 2 inches of water per week in the summer, 1 to 2 inches of water every two weeks during the spring and fall and 1 to 2 inches of water per month during the winter will be needed in order to maintain most plant life. This same scale can be used to maintain moisture in the soil. Simply water until ˝ to 1 inch of water is distributed, or until water runoff happens, which ever occurs first. Generally, we find that automatic sprinklers, which run three times a week and 10 minutes per zone during hot summer periods, will met this recommendation. Steeper sites or drought conditions may require more frequent watering over shorter duration. Remember, watering frequency decreases in the winter and increases in the summer. If you see the soil shrinking, cracking and pulling away from the foundation it is a good indication that moisture is needed. After a while you will become a good judge of when its time to water. There may be a time when you discover the soil has become very dry. You might find large ˝ to 1 inch wide cracks in the soil. When this happens, it is very important to remember that slow, consistent and uniform watering is the guideline to follow. Do not place a hose into a large soil crack and try to fill it up. The water distribution will not be uniform and you may cause an upheaval problem. In excessively dry conditions remember; water slowly, consistently and uniformly. We have now discussed proper drainage and watering concerns. That leaves us with the third consideration, plant life and trees. Trees and shrubbery can cause problems by speeding the removal of moisture from the soil. Large trees require large amounts of water and they can remove enough moisture from the soil under the foundation to cause settlement. Large shrubbery can compete for moisture in a similar fashion. Over a long period of time, large tree roots can cause uplifting of the foundation edge. Ideally. Trees should be planted far enough from the home so that the drip line of the outermost branches will not be over the home when the tree reaches maturity. Avoid planting trees and large shrubs that will grow up to become a problem. Avoid certain types of trees known for their aggressive root systems and need for water. Fast growing trees are generally the types to avoid. Three such trees are the cottonwood, weeping willow, and Chinese tallow trees. If small immature trees are found close to the foundation it is probably best to remove them now. However, what does one do when mature trees are found nearby? This is a tricky question and there are variables to consider. Trees are wondrous plants and are aesthetically desirable. Most people do not want to cut them down. Additionally, one must ask, will cutting down a large nearby tree promote root rot and termites in the supporting soils under a home? There are options to tree removal, such as root barriers, and these should be discussed with your engineer and arborist. Remember that modifying existing landscape foliage deserves case by case consideration and the final decision always depends on what you are willing to accept. In conclusion, maintenance of clay based soils requires a common sense approach to controlling moisture. The measures discussed in this article will help reduce risk but will not eliminate such. Whenever you compete against the forces of nature, there are times when your best efforts will not work. We recommend you stick with the basics, obtain professional help when needed, and hope for the best. |
Home Inspections in the Greater Houston Area
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Office 281-794-9102
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