How to Waterproof an Old Basement

Things You'll Need

  • Epoxy or latex waterproofing mix

  • Wide paintbrush

  • Bucket

  • Hydraulic cement.

  • Water

  • Mortar cement

  • Fine sand

  • Trowel

  • Waterproof paint

  • Downspout extensions

Seal your basement to keep water from seeping in.

Snow and rain saturate the soil around the foundation of your house, and the water can flow into your basement through cracks and joints in the concrete. Keep your basement dry by finding ways to keep the water out. To waterproof an old basement, start inside the basement itself, filling cracks and waterproofing the walls. Go outside when you're finished, and set up a system to keep water as far away as possible from your home and basement.

Step 1

Fill hairline cracks and holes in the walls and floors of your basement with epoxy or latex waterproofing mix. Dip a wide paintbrush into a bucket of waterproofing mix. Brush the mix over the hairline cracks and, let it dry.

Step 2

Patch cracks larger than 1/8 inch with hydraulic cement. Mix cement and water to make a mixture with a loose consistency. Pour the cement into visible cracks in the walls and floors. Pour a line of cement around the entire periphery of your basement floor where the walls meet the floor.

Step 3

Fill large leaks where you can see water seeping into your basement with a thicker mortar cement mixture. Mix one part mortar cement and two parts of fine sand with enough water to make a stiff mortar. Dip a trowel into the mortar mixture and spread it over the crack, forcing it into the crack. Don't leave any air holes. Smooth over the mortar with the trowel.

Step 4

Seal the foundation of your basement by painting a coat of waterproof paint on the walls inside your basement. Dip a wide paintbrush into the bucket of waterproof paint. Start painting on the upper corner of one wall, and cover the whole wall, top to bottom. Continue painting until all walls are covered with paint.

Step 5

Go outside to check for signs that rain water is flowing from the roof down the walls of your home and into the basement. Install extensions to the ends of the downspouts to carry rainwater as far as possible away from your foundation.