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How to Waterproof a Basement

Follow the steps in this DIY Basic to fix any leaks you might have in the basement.

More in Home Improvement

waterproof basement if moisture is noticed

Step 1: Watch an Overview Video

Step 2: Check for the Source of Wetness

To locate the source of wetness, tape a piece of foil to the inside of a foundation wall for several days. Remove the foil and check if the wall side or room side of the foil is wet. It’s possible both sides will be wet and that moisture is originating from inside and out.

foil can be an indicator of source of wetness

Step 3: Make Gutter and Downspout Repairs

Moisture on the wall side of the foil means it’s seeping in through the foundation and you may need to make gutter and downspout repairs to direct water away from the house.

moisture through foundation could be gutters

Step 4: Fill Gaps Where the Wall and Floor Meet

If water is also seeping in where the wall meets the floor, hydraulic cement can be used to fill any gaps. Prior to applying hydraulic cement open the crack up in an inverted "V" pattern with a chisel. Mix the cement, wet the area and force the cement into the area. Remove excess with a trowel and wire brush.

hydraulic cement seals gaps at wall and floor

Step 5: Apply Masonry Paint

Once you’ve eliminated the source of the moisture, applying waterproofing masonry paint will help stop any future seepage. Efflorescence is a white powdery deposit formed when naturally occurring salt compounds are drawn to the surface of masonry by water seepage. When working with muriatic acid always wear rubber gloves and eye protection and have adequate ventilation. Rinse the area thoroughly and allow it to dry completely prior to applying masonry paint.

A stiff brush and some muriatic acid will remove any salt deposits so the masonry paint bonds better to the wall. Using a stiff bristled paintbrush allows the first coat of paint to be worked into the pores of the masonry. A second coat applied with a high nap roller will assure effective waterproofing.

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