Bad drainage causes crawlspace water damage

Q: After all the rains, I finally decided to check my foundation to see if there was any water. I was surprised to find several pools of water and even more surprised to see black mold and rot on the floor of my home. When I removed some of the insulation, it was soaking wet. I have a pump in the foundation, but I never noticed it running. My neighbor said I needed to get the drains from my gutters farther away from the house. What do you suggest?

A: Not only do you need to keep the water away from the foundation, you also need some major repairs. The black mold is where the sub-flooring is decaying and sooner or later there will be a large hole in the floor.

When a homeowner sees this kind of damage, the first thought is to replace the flooring, but unless you do address the water issue, the decay will return.

Homes with a crawlspace foundation should be inspected twice a year for flooding or water entry or for decay. In most areas of the U.S., termite infestation also can be a major problem.

A semiannual inspection by a pest-control company or a certified home inspector is a wise investment to ward off the possibilities of major structural damage. We all know it’s important to change the oil in our cars every three months or 3,000 miles to prevent damage to the engine, but your home is more valuable than your car and proper maintenance should not be ignored.

The drains from the roof’s rain gutters should be directed at a minimum of 6 feet from the foundation. Homes on a hillside or homes with sloping yards may need to have the drains extended more.

Runoff drains lying on the ground are unsightly and it may be necessary to have the drains buried just under the surface of the yard.

Before digging to bury the drain, call 811 to have all the buried cables, water lines and gas lines marked so that you can avoid damage to these vital systems. The marking service is free and is available nationwide.

Improper landscaping also can allow water to enter the foundation. Loose rocks, mulch and topsoils next to the foundation can filter rain and runoff water to the foundation. Water will take the easiest path to the lowest areas of the property and landscaping is a perfect filter. In the past I have tried plastic vapor barriers to ward off the water and the weeds, but over time the plastic fails and the protective barrier had to be replaced.

I would recommend a heavy clay soil for the first layer of landscaping, compacted and sloped to drain away from the home. Adding a layer of topsoil for the plants and a bed of mulch for weed control has worked best over the years. If you have a patio, walk or driveway made of concrete or pavers, make sure they are sloped to drain properly.

If all else fails, a French drain buried around the perimeter of the foundation down to the footing is a sure-fired solution.

A French drain is a flexible plastic pipe with drain holes to allow for water entry. The pipes are covered with a fabric called a sediment sock to keep silt out of the system. After digging a trench, crushed stone is placed inside the trench, then the drain tile and then another layer of stone.

Finally, a layer of topsoil is compacted in the trench to grade level and plants (or just grass) top off the project.

Now runoff water is directed to the French drain and carried away by gravity before it has chance a to enter the crawlspace.

If the property is too low for a gravity-drained system, an exterior sump pump is installed to raise the water to where it can be drained by gravity.

For a certified home inspector in your area, go to www.ashi.org and enter your ZIP code in the “find a home inspector” link.

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.