“Hello Carl, Question for you.

We have a walk out basement facing northwest with split faced block on the outside and last year we had our contractor insulate the wall on the interior because of condensation building up on the inside of the wall in the winter.

Well this spring on a warm day I was down in the basement and noticed that there was water on the floor. Since the wall is not finished with drywall I was able to take a look and see behind the insulation and the block wall is wet.

I’m concerned about mold and I thought insulating the wall was going to stop the condensation. Our basement is heated but only at about 60 degrees, like I said it’s unfinished. Any thoughts?

Thanks, Autumn”

Hi Autumn,

You should read my page on basement insulation on www.byoh.com You are wise to be concerned about mold. Other problems such as wood rot can occur too.

Here is an excellent article on your problem from the Michigan State University Extension bulletin E-2109, Moisture Problems in the Home.

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 run off 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 ground water 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.

Again, read my page about basement insulation on www.byoh.com

I hope you are able to solve your problem,
Carl