Moisture Problems Basement Wall Condensation

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Here aresome tips on diagnosing and correcting moisture problems. Parts of this story: ~~Introduction~~ Attic andmechanical ventilation ~~ Houseson crawl spaces and other moisture sources ~~ Caulkingand weather-stripping ~~ Basementwall condensation problems

Basement wall condensation problems

Vapor barriers

Adding insulation to basement walls has advantagessimilar to adding it to wall cavities and the ceiling: iteliminates cold surfaces where condensation can occur,and it cuts energy costs. Basement walls are ofteninsulated by adding furring strips to the walls andinstalling rigid or batt insulation between the furringstrips. If you use batt insulation, install a vaporretarder such as polyethylene film on the winter warmside of the batt insulation to prevent future moisturemigration into it. To achieve a finished effect, placedrywall over the vapor retarder. (Note: There is somequestion about using a second layer of polyethylene whenbatt insulation is used on basement walls.)

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

Seepage and leakage

Seepage or leakage problems commonly occur in thebasement or crawl space in the early spring when snow andice are melting and frost is beginning to leave theground. 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 mayappear as a damp spot in an isolated area or in manyspots. Leakage, on the other hand, is the fast(pressurized) movement of groundwater through the wall. Inthe case of leakage, the entry routes for the water arecracks or joints in the wall; with seepage, the watermigrates through pores in the wall material.

Two conditions must exist for seepage or leakage tooccur. First, the soil near the basement or foundationwalls must be wet or saturated. Second, the basement orfoundation wall must have a weak spot where waterinfiltration can occur.

Soil saturation

wet soil

Wet or saturated soil near basement walls can haveseveral causes: improper disposal of roof water runoff,poor surface drainage away from the house, separationbetween the basement or foundation wall and the soilsurrounding it (this crack acts like a funnel), windowwells collecting rain water, lawn sprinklers located too
close to the house, an inadequate below-ground footingdrain system or a high water table.

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

Alleviate wet or saturated soil near the basementwalls by minimizing or eliminating the moisture at itssource. The installation, repair and maintenance of thegutter, downspouts and eaves trough discharge system arenecessary to minimize the ponding of roof water runoffclose to the foundation. Eaves trough discharges
should terminate at least 3 feet away from the basement/foundation wall and gently slope away from thefoundationat least 1 inch per foot of discharge run.

preventing wet soil

An adequate ground slope away from thebasement/foundation wall is needed to ensure thatrainwater will be distributed away from the foundation.Generally, a slope of 6 inches in a 10-foot run of groundis adequate. All pockets or openings between the soil andthe foundation should be filled with clean materialthat has good drainage characteristics, such as pea graveland sandy soil.

Window well covers should be installed so thatrain-water will not collect in the wells. Locate lawnsprinklers 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 youare an experienced do-it-yourselfer) to drain excessgroundwater away from the tile system and discharge itinto a sump well set in the basement floor. In turn, thesump can then pump the waste water into the storm sewersystem or to a ground area adjacent to the house. Choose aspot where the water will not damage the foundation or anyadjoining property. Contact your local township or citybuilding officials for specific guidelines on where todispose of sump pump discharge.

Wall Repair and Conditioning

crack repair
For larger foundation cracks, chisel out a dove-tail groove and clean and fill with mortar or hydraulic cement.

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

Installing a footing drainage system

foot drain

An additional solution for serious basement moistureseepage/leakage problems is installing a footing draintile system around the exterior walls. While this isbeing done, the exterior side of the foundation wallsshould be waterproofed. This solution involvesexcavating the soil around the exterior walls, installinga footing drain tile system, waterproofing the wall,backfilling with clean and porous material, and slopingthe backfill away from the walls. Contact your localtownship or city building official to secure informationabout discharge of footing drain tile water.

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

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

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