How to Limewash a Concrete and Sand Wall Below the Grade Interior Foundation

Prepare the wall. Rough walls need to be cleaned of all dust, dirt and cobwebs. If the concrete and sand wall is very smooth, use a wire brush to roughen its surface. Remove any paint or other nonabsorbent coatings. This allows the lime to “key” correctly into the masonry.

Dampen the wall's surface. Use a spray bottle filled with water to pre-wet the area you intend to limewash. The wall should be lightly damp, not soaking wet.

Make the limewash. Mix lime and water together in a bucket to create a solution of about 15 to 20 percent lime and 80 to 85 percent water. Limewash should have a consistency similar to that of whole milk and contain no lumps or large granules. If you want to color the limewash, mix in a color-fast pigment, such as yellow ocher or ultramarine.

Apply the first coat. Swirl a longhair masonry brush in the limewash to keep the lime in suspension. Cover the dampened foundation with a thin layer of limewash. The wash will be relatively transparent when wet but will become more opaque as it dries. Apply the wash liberally in brushstrokes from many different directions to work it into the wall.

Add more coats of limewash. As soon as the limewash no longer lifts off the wall, it is dry enough for another coat. Apply five or more thin layers of limewash for best results. Allow the wall to dry for several hours or overnight. It has cured completely when it no longer feels cool to the touch.