But, the damage it can cause can be expensive to correct. Even a small amount of water under a house can cause wood rot, mildew, insulation deterioration, electrical problems, warped wood floors and raised humidity in the home. These conditions are an invitation for termite infestation, as well. Concrete slab foundations can also be affected by water drainage problems. Excessive moisture can actually move the slab, causing cracks on interior walls and ceiling.
Water causes the clay in expansive soils to swell, and foundations can be seriously damaged. .
Prevention Don't allow roof drains and gutter pipes to spill out next to the foundation. If possible, direct roof water to closed pipes that empty onto the street. Make sure soil and walkways next to the foundation slope so that rainwater will flow away from the house. These are the single most important steps you can take to minimize water damage to your home. Plan your landscape watering to give just the amount of water the plants need.