Fixing a Wet Basement

It is estimated by the American Society of Home Inspectors that 60% of U.S. homes have wet basements. Even if you had not previously had any problems with a wet basement a very wet year like we’ve just had in the southeast can uncover new or suddenly bigger problems.

Water or moisture in a basement can come from three sources: seepage of groundwater, condensation and rain. Condensation often occurs where cold meets warm air. Groundwater often happens in soils with a high clay contents after a heavy storm, but quickly dissipates in a day or two. However, most often basements get wet when rainwater or melted snow runs toward the walls of houses from roofs, yards and driveways and infiltrates.

Concrete is not waterproof neither is cinder blocks or mortared stones or bricks. Overtime mortar cracks and water that isn't routed away from the house percolates through porous topsoil and then stops at the compact soil near the base of the foundation. Hydro-static pressure forces the water through gaps or cracks in walls and footings. Water also moves through porous walls by capillary action.

Even modern homes built with an existing underground French drainage system can after a decade or two begin to have wet basement problems. Unfortunately, the drainage system often breaks apart or fills with silt over time.

Depending on how bad your moisture problem is there are a few cheap and effective solutions to try first. Simply moving the water away from the house may solve your problems. First thing you should do is check your gutters and downspouts. Clean out the gutters, repair or replace any damaged gutters and extend your downspouts away from your house. Water from down spouts should be directed away from the house, discharging at least a few feet from the foundation. If the natural flow of water is to pool in any location, it may be advisable to direct all down spouts to a dry well system or pipe to a more natural drainage location. In my own home I utilized the natural slope of my yard and a French drain to move all the water from my downspouts away from the house and to a rain garden.

Next, rain water should not run up against the house (nor should plant irrigation water). The soil level against the exterior walls should slope away from the home and often after years of mulching your beds this is no longer true. Fix it.

Even in areas where the natural topography is towards the house an artificial slope should be created in a shallow “V” to prevent water from pooling around the foundation. The ground around the home's foundation should be graded to slope down and away from the house at a rate of 1/2" to 1" per linear foot to drain surface water away from the house. If needed, a French drain should be dug to an adequate distance from the house. Most houses are built with the soil level sloped away from the building, but landscaping and time can undermine this. Plants should not be planted closely against a structure to avoid “watering the building” instead of the plants.

Test any underground drains with a hose to make sure they are working properly. Often underground drains become blocked with debris or broken and allow water to drain against the building. Drains that are not working should be repaired or replaced. Be sure that driveways, sidewalks, and patios slope down and away from foundation walls at 1/4" per linear foot.

If these solutions do not eliminate a moisture problem then the next steps will have to be taken. In extreme cases, you may have to dig out around the foundation and replace the fill with an exterior drain tile and with a good draining material such clean gravel. Replacing an entire exterior French drainage systems on a fully subterranean basement, is the most complicated and expensive solution. This is true because it requires removing the landscaping, excavating to expose the foundation, covering it with a waterproof membrane and laying perimeter footing drains in a bed of gravel at the base of the footings. Because this can be very expensive in existing homes, all the previous solutions should be rigorously tried first. With a basement that is mostly daylight this can often be accomplished for a more modest cost.

A lower cost alternative often suggested by waterproofing contractors would be to install an interior drainage system. This is still expensive and messy, but is more easily accomplished. When an interior drainage system is installed it is usually combined with a sump pump sometimes with lateral drains, a dehumidifier and wall curbs or wall weeping systems. Basically, a waterproofing contractor will recommend installing most of these systems to ensure your basement stays dry. This is also very expensive and messy, but is extremely effective. Get more than one bid and check references and warranty. My experience in contracting the work at my mother’s home was the prices varied by over 50% and quality, warranty and reputation were not correlated with price.