How to Prevent Flooding and Foundation Damage
We often experience heavy soaking rain which flood yards and damage foundations here in Texas. Too much water is never good for a foundation no matter where you are in the country. In Texas, however, water is especially damaging because of the expansive clay soil that’s common to this region. Expansive clay soil increases in volume when it gets wet. When it expands, this soil can exert as much as 15,000 pounds per square foot against a foundation. Therefore, keeping your foundation intact during times of heavy rain requires proper drainage of your property.
What If I Have a Drainage Problem?
If you have a drainage problem, be sure that you have covered the basics before considering drainage systems. These basics include a properly cleaned and maintained roof gutter that covers the entire perimeter of your roof with a downspout that discharges water at least 3 feet from your house. Your property should slope down and away from your home by at least 6 inches down for every 10 feet of horizontal distance. Hard surfaces such as sidewalks and driveways should not pool or channel water toward your house.
Types of Drainage Systems
Sometimes grading your property isn’t feasible because it’s bowl-shaped with your house at the bottom, or because your house is on the side of a hill. In cases such as these, installing drainage systems is more cost-effective.
Surface drains collect surface water that’s pooled in low spots. The water flows into catch basins that are flush with the ground and connect to an underground drain pipe. The pipe slopes downhill so that water flows to the street drainage system or some other acceptable drainage point. Grates on the catch basins prevent debris from entering and clogging the drainpipes.
Channel drains collect surface water on hard surfaces such as your driveway or the concrete of your patio. The water is drained via an underground sloping pipe that discharges the water at the street or some other viable drainage point.
Sometimes water still reaches your foundation even though the surface water has been properly drained. Where is this water coming from? The answer is subsurface water flow. All things being equal, water ought to percolate straight down into the soil since that’s the direction of gravity. However, the soil’s ability to absorb moisture (its permeability) can change with depth. On a hillside, sometimes the soil deeper down is less permeable than the soil above it. After rain penetrates the upper soil layer of the hillside, the water is unable to penetrate the less permeable soil beneath and therefore follows the slope of this layer down the side of the hill. This water flow is underground. If your house is on the side of this hill or at its bottom, this subsurface flow can damage your foundation.
French drains are designed to catch this subsurface water flow before it reaches your foundation. A French drain is a trench that’s lined with a filter fabric with a perforated PVC pipe lying at its bottom. Gravel fills in the rest of the trench to within a few inches of the surface. The remaining filter fabric is folded over the top of the gravel and the rest of the trench is filled in with soil. Grass is then planted on top.
Subsurface water flows into the side of the trench, goes through the filter fabric and gravel, and enters the perforated pipe. The pipe slopes downhill so that water is drained away to a safe discharge area. Always include a filter fabric in your French drain because it prevents soil from getting into and clogging the pipe.
If you have questions, concerns, or problems with the drainage of your property or with your foundation, Perma-Pier Foundation Repair of Texas is here to help you. Contact us today.