Homefix: Dwight Barnett answers home-improvement questions. This week's topic is on water coming into a crawlspace or basement. Tips include using landscaping and rain-gutter downspouts to divert water.

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I have received a number of questions about flooding of crawlspace and basement foundations. Here are some suggestions to help prevent flooding in the future.

As soon as the weather in your area permits, the crawlspace and basement foundation should be inspected for signs of flooding. Any water that has collected in the foundation should be removed as soon as possible.

Water left in the crawlspace or basement can cause serious damage to the home’s structure and foundation. Damaged items in a basement should be moved to storage areas to dry and any items that have mold should be discarded.

In order to prevent flooding, it is important to direct all runoff water away from foundations. My experience has shown that the No. 1 cause of flooding is inadequate or poorly maintained roof rain gutters. Rain gutters need to be inspected and maintained semiannually.

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All the runoff from the home’s roof is directed to the rain gutters. If they leak, are loose-fitting or are clogged with debris, the water pours over or around the gutters and collects next to the foundation. As the water pours over the gutters, the soil next to the foundation erodes, allowing water to form pools instead of draining away.

Proper annual landscaping will give you the opportunity to correct the eroded areas. Compacted clay soil next to the foundation topped with planting soils will divert water away from the home.

The yard should slope at least 6 inches in the first 10 feet on all sides of the foundation. If this is not possible, a French drain or a swale can be installed. A French drain is a perforated plastic pipe buried just beneath the soil and embedded in gravel or crushed stone. The pipe should be designed to drain by gravity to a suitable location. As water collects in the area it will soak into the French drain and be carried away from the foundation.

If you have splash blocks for the gutter’s downspout drains, I would strongly recommend you install extension drains to direct the runoff water at least 6 feet from the foundation. Splash blocks prevent erosion, but they do not prevent pooling or flooding.

Inspect all concrete slabs near the foundation. This includes walks, driveways, porches and patios. These slabs must be sloped to drain away from the foundation. If the concrete is cracked and has settled, it should either be replaced or “slab jacked”to prevent flooding. Slab jacking is a process in which grout is pumped under the concrete slab to elevate the slab for proper drainage. Also inspect the landscaping between the foundation and the concrete slabs. Try to determine how rainwater from the landscaping will drain over the concrete slab. If you have landscape borders next to the concrete, they will act as dams holding the runoff water in the soil. There should be openings in the borders to allow any accumulated water to drain.

If your landscaping utilizes decorative gravel or wood chips, the soil underneath should be properly sloped for drainage. Low areas that have been filled with gravel will form pools that can seep to the foundation. Window wells, access doors and foundation vents are openings in the foundation wall that are subject to flooding.

Semicircle rings of galvanized steel called “area walls” can be installed to help prevent flooding. Area walls are available in various sizes to fit common-access door and window openings. For large area walls, plastic covers are available to keep direct rains out of the openings.

If you have major water problems, contact a qualified home inspector to help you in determining what actions need to be taken to correct the problems. Qualified home inspectors can be found at www.ashi.org.

Dwight Barnett is a certified master inspector with the American Society of Home Inspectors. Write to him with home-improvement questions at d.Barnett@insightbb.com.