Moisture problems

Here are some tips on diagnosing and correcting moisture problems. Parts of this story: | Introduction | Attic and mechanical ventilation | Houses on crawl spaces and other moisture sources | Caulking and weather-stripping | Basement wall condensation problems

Adding insulation to basement walls has advantages similar to adding it to wall cavities and the ceiling: it eliminates cold surfaces where condensation can occur, and it cuts energy costs. Basement walls are often insulated by adding furring strips to the walls and installing rigid or batt insulation between the furring strips. If you use batt insulation, install a vapor retarder such as polyethylene film on the winter warm side of the batt insulation to prevent future moisture migration into it. To achieve a finished effect, place drywall over the vapor retarder. (Note: There is some question about using a second layer of polyethylene when batt insulation is used on basement walls.)

Rigid insulation is relatively impervious to water and moisture vapor damage. Therefore, it does not require the addition of a vapor retarder over or behind it when it is added to basement walls. As with batt insulation, drywall can and should be used over rigid insulation to provide a finished look and, in accordance with building codes, to provide a fire protective covering over the material that separates it from a habitable living space. Keep in mind, too, that if condensation is occurring in the basement during humid summer weather, windows and doors to the basement should be closed to help keep the humid air out. Open doors and windows when outside humidity levels are low to introduce dry air into the basement.

Seepage and leakage

Seepage or leakage problems commonly occur in the basement or crawl space in the early spring when snow and ice are melting and frost is beginning to leave the ground. They can also occur in the spring, summer and
fall during and after heavy rains.

Seepage in a basement is the slow (non-pressurized) movement of groundwater through the basement walls. It may appear as a damp spot in an isolated area or in many spots. Leakage, on the other hand, is the fast (pressurized) movement of groundwater through the wall. In the case of leakage, the entry routes for the water are cracks or joints in the wall; with seepage, the water migrates through pores in the wall material.

Two conditions must exist for seepage or leakage to occur. First, the soil near the basement or foundation walls must be wet or saturated. Second, the basement or foundation wall must have a weak spot where water infiltration can occur.

Soil saturation

Wet or saturated soil near basement walls can have several causes: improper disposal of roof water runoff, poor surface drainage away from the house, separation between the basement or foundation wall and the soil surrounding it (this crack acts like a funnel), window wells collecting rain water, lawn sprinklers located too
close to the house, an inadequate below-ground footing drain system or a high water table.

Once the soil is wet or saturated, cracks, weak joints or pores in the masonry provide a route through the
basement or foundation wall.

Alleviate wet or saturated soil near the basement walls by minimizing or eliminating the moisture at its source. The installation, repair and maintenance of the gutter, downspouts and eaves trough discharge system are necessary to minimize the ponding of roof water runoff close to the foundation. Eaves trough discharges
should terminate at least 3 feet away from the basement/foundation wall and gently slope away from the foundation at least 1 inch per foot of discharge run.

An adequate ground slope away from the basement/foundation wall is needed to ensure that rainwater will be distributed away from the foundation. Generally, a slope of 6 inches in a 10-foot run of ground is adequate. All pockets or openings between the soil and the foundation should be filled with clean material that has good drainage characteristics, such as pea gravel and sandy soil.

Window well covers should be installed so that rain-water will not collect in the wells. Locate lawn sprinklers so they don't sprinkle the walls.

A sump pump can be attached to the footing drain tile (a building contractor will be needed for this unless you are an experienced do-it-yourselfer) to drain excess groundwater away from the tile system and discharge it into a sump well set in the basement floor. In turn, the sump can then pump the waste water into the storm sewer system or to a ground area adjacent to the house. Choose a spot where the water will not damage the foundation or any adjoining property. Contact your local township or city building officials for specific guidelines on where to dispose of sump pump discharge.

Wall Repair and Conditioning

If the seepage or leakage is occurring through a small, visible crack, use a wire brush to clean the crack and fill it with mortar cement or hydraulic cement. For larger cracks, chisel out a dove-tail groove and clean and fill the groove with either mortar or hydraulic cement. If leakage is heavy or under pressure, you may need to install weep pipes to direct the leakage to a sump pump or drain. A professional may have to be hired to help with these methods.

An additional solution for serious basement moisture seepage/leakage problems is installing a footing drain tile system around the exterior walls. While this is being done, the exterior side of the foundation walls should be waterproofed. This solution involves excavating the soil around the exterior walls, installing a footing drain tile system, waterproofing the wall, backfilling with clean and porous material, and sloping the backfill away from the walls. Contact your local township or city building official to secure information about discharge of footing drain tile water.

The addition of a footing drain tile, weep pipes and the procedures involved in attaching an existing footing drain tile to a sump pump are expensive and time consuming. Consult an experienced building contractor, engineer or architect before attempting these solutions. Before you hire anyone to do such a job, look for background information about these people. How long have they been in business in or near your community? What type of reputation do they have with local banks, savings and loans associations, or lumberyards? Are they licensed? Ask for the names of at least three references who have had work similar to your done by the individuals or their companies. Ask these people if they were satisfied that their problems were correctly identified and solved. Finally determine if working arrangements and business dealings between the references and the contractor were comfortably and professionally handled.

The information in this article comes from Michigan State University Extension bulletin E-2109, Moisture Problems in the Home.