In my previous two blogs (Parts 1& 2), I discussed the reasons for the “requirement” for Texas homeowners to add water to the soils around their slab foundation. It is suggested that these two documents be read in conjunction with Part 3.
Buried Drip Irrigation Systems:
The installation of a buried drip system (hooked up to the lawn irrigation system) to water the soils around the foundation is becoming more common and is certainly more convenient than using soaker hoses that lay on the surface.
However, I have heard of a few examples where a homeowner installed a buried drip irrigation system and immediately began an aggressive watering program. Unfortunately, the sudden increase in moisture caused the clay soils to expand and heaved their slab foundation upward. However, I have also seen a homeowner move into a residence and began “normal” (not aggressive) watering of the lawn and foundation and their foundation still heaved upwards several inches.
Too much water can be just as bad as too little. In fact, too much water in the “right” soil conditions (dry expansive clay soils) can lead to catastrophic results, causing upheaval of the foundation. Unfortunately, since soil conditions in North Texas vary from one neighborhood to another, there is no single watering solution that will cover all areas.
I must state again that the homeowner must exercise caution when the slab foundation is on dry expansive clay soils because too much water can expand the soil and damage the foundation.
It is best to allow Mother Nature increase the soil moisture content (for example, during or soon after the normal winter/spring rains) and then the homeowner starts his water program before the soils begin to dry. For example, as I am writing this blog, the soils in North Texas (DFW area and north) are saturated because of all the rain we have had this winter. At my home, I could not add any more water to the dirt, even if I wanted to. Because of this, generally speaking, the slab foundations in North Texas are currently performing as good as they have in years.
I do not consider myself an “expert” on buried drip irrigation systems nor have I studied how the industry is currently installing these drip systems but a few miscellaneous comments / observations are:
• The few foundation drip systems I have seen consist of small diameter black tubing that is buried a few inches from the foundation. It seems to me that this thin wall tubing could easily be cut with a shovel. If this occurred, it could be similar to having a plumbing leak under/near the slab. It would be better if the drip line is made up of thicker wall pipe that would be harder to damage.
• Some of the drip systems I have seen are buried only inches away from the foundation and only a few inches deep. I prefer that a drip system be buried a foot or so deep and be about 18” from the foundation. (If the drip system is to be installed in an area where the ground surface is sharply sloped, the placement of the drip line may need to be modified to minimize the amount of water running downhill away from the house.)
• The drip line should be marked to alert anyone digging in the area that there is plumbing below.
• I have seen one buried drip system where the drip line is installed in a bed of pea gravel. This would not only aid in alerting someone digging in the area that there is a plumbing line below but it would help disperse the water. If this technique is used by a homeowner, I recommend wrapping the pea gravel in a drainage fabric to keep the gravel from silting up.
• Obviously, the system I generally described above is much more expensive than the normal drip systems that I have seen recently.
• I have heard of some buried drip tubing lines that have been chewed on by varmints.
• I have also heard about some types of emitters, if buried, will eventually get clogged up with roots.
• The drip system must be monitored for leaks.
• If the clay soil around a foundation is in a desiccated state, do NOT suddenly put a lot of water into the soils. To do so, may cause permanent upheaval of the slab. Upheaval can be a most difficult, if not impossible, thing to attempt to remedy.
• It is generally accepted that a homeowner should check to see if the soil is pulling away (separating) from the foundation. If so, it is an indication that the soil is becoming desiccated and water should be added to the soil. DO NOT pour water down the separation!
I have witnessed a few newly constructed homes where the slab was constructed on expansive, dry clay soils and after the homeowner began his normal watering of the landscaping with a sprinkler system, the clay soils expanded and heaved their homes upward a few inches.
There is not an easy answer or remedy for this situation. Hopefully, the reader is not in this predicament, but if he is, he should contact the builder and/or the structural engineer who designed his foundation (or the geotechnical engineer who conducted the soil study) and ask them for advice.
• I once had a client who used a moisture meter to measure the soil moisture content around his foundation once a week. If an area was dry, he would add water.
• To repeat: Too much water can be just as bad as too little; even worse, depending on your soil conditions. Determining how much water to add to the soils is somewhat subjective and requires some experimentation and there is no “one size fits all” answer. In other words, there are many, many variables involved in determining how much, how often to water the soils around the foundation.
I highly recommend that the homeowner retain the services of an experienced engineer to review his particular situation and make recommendations as to how much to “water” the soils (even he will guess, albeit it will be an educated guess).
• Even though the theory of keeping the soil around the foundation at a constant moisture content is valid, practically speaking, it is a difficult thing to do.
• Because of the potential problems with a buried drip system for the foundation, I am not yet a fan.
Proceed with caution no matter what system you use to water the clay soils around your foundation!