How to Waterproof Interior Basement Walls

Sealing your basement walls can help prevent damage caused by excess moisture.

Keeping your basement dry can be a challenge, especially during heavy rain or spring melts. Applying a waterproof sealer to the interior of the basement walls can help alleviate many moisture problems. Applying the sealer is as easy as rolling on paint; however, it takes a lot of work to prepare the walls for sealing. With the right tools, you can waterproof interior basement walls in a weekend.

Things You'll Need

• Wire brush
• Concrete cleaner
• Sprayer
• Stiff brush
• Chisel
• Hydraulic cement
• Trowel
• Paint pan
• Paint roller

Instructions

1. Remove any loose paint, concrete, dirt or other debris from the walls with a wire brush. Brush the area around cracks or penetrations thoroughly to prepare them for the hydraulic cement.

2. Clean the interior basement walls with a concrete cleaner that contains degreaser. Follow the manufacturer's instructions for mixing the cleaner. Apply it with a sprayer to speed up the process. Scrub the walls with a stiff brush to remove grease, scale and other impurities. Rinse the wall and allow it to dry according to the instructions on the cleaner.

3. Chisel loose concrete away from any cracks or holes in the walls. Use a chisel to undercut the edges of cracks and holes to help the hydraulic cement bond to the walls.

4. Mix small batches of hydraulic cement according to the instructions. Work the cement into cracks and holes, making sure to completely seal these with cement. Smooth the surface of the hydraulic cement with a trowel until it is flush with the surface of the basement walls. Allow the cement to cure according to the instructions.

5. Roll on the waterproofing primer, if applicable, using a thick-nap roller and paint pan. Work the primer into the corners of the walls, being sure to coat the area around the crack and hole repairs thoroughly. Allow the primer to dry and apply a second coat, if necessary.

6. Waterproof the interior basement walls by rolling the waterproofing sealant onto the walls with a thick-nap roller. Make sure the repaired areas are well sealed. Coat the edges and corners thoroughly with the sealant. Allow the sealant to dry according to instructions. Apply a second coat, if needed.

Tips & Warnings

• Before you waterproof interior basement walls, check that the moisture is an external problem. Tape a piece of plastic against a damp spot on the wall. Inspect it the next day to see if the moisture is on the wall-side of the plastic, indicating an external moisture problem, or on the living area side of the plastic, indicating an indoor humidity problem.

• Wear eye protection when scrubbing, cleaning and chiseling the concrete wall. Make sure the work area is adequately ventilated before applying the waterproof sealant.

References

• Masterchem; Kilz; Masonry Waterproofing Paint
• Sanit-Tred: Do It Yourself Basement Waterproofing
• RadonSeal: Basement Waterproofing Sealer

Resources

• Read this Article in Spanish