Several different types of foundations are common in the Houston area including post tension, structural steel, pier & beam or block & beam. The commonality of these foundations is they support a structural and rest on the soil. In other words, soils support the foundation.
Many times issues with the foundation occur during periods of drought or large amounts of rain. What can be done about too much rain and how do I know if the grade is sufficient?
Here’s the official word on slope and elevations based upon the International Residential Code (IRC): The grade elevation should be 4” below the brick veneer and or 6” below the exterior veneers (all other types), and fall away from the foundation (6” in the first 10’ where possible). IRC R404.1.6 & R401.3
If you cannot correct the grade or the slope isn’t sufficient French drains or underground drains may be required. Finally go outside (watch for lighting) to know for sure what the water flow and patterns are like during a heavy rain.
Addressing periods of drought is important for the foundation. Here’s a phrase I include in inspection reports when dry soils are present: The soils are dry and have pulled away from the foundation. Soils support the foundation. Due to the expansive nature of the soils in the Houston area, a frequent-foundation watering program is recommended. Consistent watering at the entire slab perimeter may help prevent further and/or future settlement and damage.
A watering program should be established during periods of drought. You can extend the amount of time for watering with your lawn sprinklers or sprinkler system (make sure not to spray on house possibly causing damage). I would also recommend a hydrometer (available from a garden center or box store) to check moisture levels below the first couple of inches of soil. Lawn sprinklers should be checked for leaks including connections at sprinkler heads.
A more formal program may also be started by using a piping system around the perimeter of the dwelling. The least costly would be a black soaker hose buried several inches underground 1’ from the house. A quick disconnect can make the connection from the hose bib (outside faucet) to the soaker hose. I use a timer on the hose bib set from 1-2hours depending upon how dry it is and water 2-3 times per week. Check exposures of the house (i.e. South & West) to see if certain areas require more or less water.
Tree and large shrubs can rob a foundation of moisture. Tree roots may mirror the canopy and can be up to 50% larger. Large shrubs and tree should be planted away from the foundation accounting for future growth. If removal of a large tree is necessary a certified arborist should be consulted. Many inspectors report trees or shrubs in an inspection report if they are within 5’ of the slab perimeter. How was 5’ decided upon? It’s not a code or city requirement, it was an arbitrary distance decided upon by old FHA guidelines.
Management of moisture content around the slab perimeter is the first line of defense against problems with your homes foundation.
