How to Waterproof a Concrete Basement Floor

  • 24-48 hours
  • Intermediate
  • $70-300
What You'll Need
Mixing attachment
Silicone tape
Pastry bag
Waterproof paint
Paint tray
Wet and dry vacuum
Wire brush

Homeowners often neglect concrete basement floors when waterproofing the basement. It is a terrible mistake, as a concrete basement floor is the one area of the basement towards which water flows naturally. That is why most builders create drain areas in obscure places in the basement floor which lead through a concrete shaft to the soil under the home.

The walls are usually where the water enters the basement, but it rests on the concrete basement floor and erodes the concrete. In good home construction, the exterior basement walls are coated with waterproof paint and drainage placed. You can waterproof your concrete basement floor yourself by following these steps.

Step 1 - Prepare the Concrete Basement Floor

Prepare the basement floor for the process. Sweep it clean so that the paint will be set without voids. Walk the floor and look for cracks and holes in the surface of the floor. Use the wire brush to clean the sides of the cracks. Doing so removes loose concrete so that you can remove it with a wet/dry vacuum.

Step 2 - Patch the Concrete

To effectively waterproof the concrete basement floor, it must be be patched, as any crack could be an access point for water. Read the instructions on the bag of concrete and mix it with water in the bucket. Use the drill’s mixing attachment to stir the contents until the concrete has the consistency of oatmeal. The holes and cracks in a concrete floor are often small; patching them with too much concrete is a waste of time and money.

Once the concrete is mixed, fill a pastry bag and apply it to the cracks and holes. Let the concrete overflow and use the trowel to spread it. Doing so not only fills the cracks and holes, but will also anchor it to the main floor. Wait for the concrete to dry, then sand it until it is flush with the floor.

Step 3 - Edging

The edges of the concrete basement floor have a tendency to separate from the walls in older homes. Take a preemptive measure and apply concrete along the edges of the floor using the pastry bag. Once the concrete has dried, tape the seams with silicone tape and cover the area with concrete.

Step 4 - Painting

The final step in waterproofing your concrete basement floors is painting them with waterproof paint. Mix the paint and pour it into the paint tray. Use a regular paintbrush to apply the paint to the floor so that you do not neglect any divots. Use a roller to even the paint or to apply a second coat.

WARNING: Check the waterproof paint's container to see if it has any safety instructions and open any windows to give the basement ventilation while you're working.