How to Waterproof Your Basement

One of the most frustrating problems faced by homeowners is the constant battle against wet basement walls. Luckily, basement waterproofing is a DIY project you can finish with a little time and effort.

Waterproofing protects basement walls and other masonry surfaces from the damaging effects of water penetration. It seals porous masonry walls above and below the ground level, penetrating the masonry’s tiny pores to form a watertight coating. This stops leaks and holds back the flow of water, even under pressure, and helps keep basements dry.

Step 1: Find the Source of the Problem

A wet basement wall might be a symptom of a larger problem. Water may be coming in from a variety of sources — leaky downspouts or gutters, blocked drainage pipes, improper grading or ruts that direct ground runoff toward your foundation. Correcting these problems, along with waterproofing your basement walls, is the best way to prevent masonry surfaces from leaking.

You should find out if seepage or condensation is causing your wet walls. To test this, tightly tape a one-foot square of aluminum foil to an interior basement wall, removing it after several days. If the room side of the foil is wet, the problem is condensation. Using a dehumidifier in your basement should help get rid of condensation. If the wall side is wet, the problem is seepage. Both problems can occur at the same time.

Another source of water seepage could be an area often times overlooked — the floor/wall joint. When concrete floors cure, they shrink and pull away from the wall, allowing a space for water to enter. Seal all gaps between floor and walls with hydraulic cement.

Step 2: Surface Preparation

Just like any painting job, surface preparation is a critical step. Loose or broken mortar, dirt, dust and other debris should always be removed before putting on a new coat of paint.

Before applying the waterproofer, clean the surface thoroughly. Waterproofing works best when applied to a clean, bare masonry surface.

To remove old paint, use a wire brush or sandblast the surface. Use muriatic acid to get rid of efflorescence—the white, crystal-like salt deposits that will prevent the waterproofer from sticking to the wall. Any holes should be patched with hydraulic cement.

Safety Alerts!

Muriatic acid is highly corrosive and can be harmful to your skin. Wear protective clothing, safety goggles and protective gloves when working with muriatic acid.

The fumes from muriatic acid can also be harmful. Be sure you’re working in an area with

Muriatic acid can also damage other surfaces. Take care when applying the muriatic acid to walls.

Step 3: Apply the Waterproofer

Now that you’ve prepped the surface, you’re ready to apply waterproofer to your basement walls. For best results, apply the first coat with a nylon or polyester bristle brush. The second coat can be applied with a brush or masonry roller. Work waterproofer thoroughly into the pores of the masonry. After using the first gallon, measure the area covered. It should be about 75 to 100 square feet. If the area is more than this, you’re spreading the waterproofer too thin.

Apply a second coat over the entire wall surface. If seepage is still present after several days, tiny pores or pinholes are still open. Apply an additional coat to these areas.

Helpful Tip

Waterproofer won’t adhere to a wall with a temperature less than 50ºF.

Most waterproofers aren’t made to withstand foot traffic, so don’t try to waterproof your basement floors.

Congratulations! You’ve just waterproofed your basement, a DIY project that will help keep your basement dry for years to come.

Project Shopping List

Here’s what you’ll need to complete this project successfully.