How Do I Waterproof My Basement From the Inside?

Before you coat anything, look for cracks, gaps, and efflorescence on walls and floors. Use a wire brush to remove loose material and clean the surfaces thoroughly. Check for signs of previous repairs that may have failed.

Identify where water enters. Cracks in the foundation, gaps around pipes, and wall-floor joints are common spots. A water damage inspection can pinpoint hidden issues. Knowing the source helps you choose the right sealant and coating.

• Cracks wider than 1/8 inch may need epoxy injection
• Hairline cracks can be filled with hydraulic cement
• Check the drainage tile and any floor drain
• Look for mold or musty odors
• Test the floor for moisture with plastic sheeting

Choose a waterproofing paint or a cementitious coating designed for interior masonry. These products create a barrier against moisture vapor. Apply two coats with a roller or brush, following the manufacturer's directions for temperature and drying time.

Make sure the surface is dry and clean of dust. If the wall is damp, the coating may not bond. In a hot semi-arid climate like Fresno, dry conditions work in your favor. However, do not apply the coating during or right after heavy rain.

• Cementitious coatings are durable and breathable
• Acrylic coatings are easy to apply and clean up
• Epoxy coatings provide a hard, glossy finish
• Check if the product is suitable for below-grade use
• Apply a second coat after the first is dry to the touch

Interior waterproofing is only a partial solution. Water that builds up outside will find a way in. Extend downspouts away from the foundation, and grade the soil so it slopes away. Clean gutters regularly to prevent overflow.