April 6, 1997

Solving water in the basement

By Dan Bowers - Holmes Inspection Co.

With the exception of an occasional problem with an underground spring, the source of 95 percent of problems with water in the basement is rain from the sky. The remaining percentage may be due to a high water table or sewer backups.

The primary cause of water in the basement is poor grading outside the house where the slope of the yard grade is toward the house. Detached or failed gutters and downspouts that do not divert water away from the walls of the house also contribute considerably to water problems.

The solution to water in the basement caused by poor grading is easy to understand but may be costly to implement. But a solution is necessary.

To identify the problem areas, walk around the house and look for any depressions in the soil. The common places are at downspouts and the walls close to the house, especially those adjacent to window wells, chimneys and concrete slabs or steps.

When you locate the depressions or low spots, you must remove the soft soils and then create a positive slop away from the house with a dense soil, such as clay. Then bring back the soft soil on sop of the clay. Soft soils may include topsoil, sod or mulch. These soils have very high air content and tend to hold water like a sponge. Typical top soil is about 40 percent air.

Also, be sure to remove any sand or stone away from the walls of the house, as water will filter through the sand or gravel, accumulate at the bottom and eventually find an opening in the masonry basement wall.

If landscaping, flower beds or concrete patios or walks have to be replaced, it may not be practical to regrade.

A generally accepted solution is to install a drainage system with a sump pump in the basement crawl space to receive water that enters the area, A sump pump will discharge water that enters, but it, does not address the cause of the problem. In addition, the water that enters still causes high humidity, which, in turn, affects your comfort level and may cause mold to develop.

In the majority of cases, regrading is less expensive than a drainage system and sump pump because only low areas have to he addressed. Regrading may cost $20 to $30 per linear foot if flower beds or shrubs do not inhibit work.

And in most cases, only a portion of the perimeter has to be addressed. Regrading costs may range from a few hundred dollars to address low areas or downspout extensions alone to $3,000 to $3,500 to regrade the perimeter for a house that is about 30 feet by 35 feet.

The drainage system, called a hydrostatic pressure relief system, typically goes around the perimeter of the basement. The cost is generally $25 to $35 per linear foot, plus $400 to $500 for the pump, rock, discharge piping and electric outlet. If your home has a 30-by-35- foot basement, the cost for a French drain may he $4,000 to $5,000.

Dan Bowers is a certified member of the American Society of Home Inspectors.