How to Apply Water Seal in a Basement

Even if you don't have an obvious leak in your basement, a cement floor or concrete-block wall can feel damp from slow seepage of water. If you're planning to paint or lay carpet in your basement, apply a sealer to the walls or floor first to control dampness. Masonry sealers come pre-mixed or in powder form that must be mixed before use. They can't fill large cracks, so repair any obvious gaps with hydraulic cement and allow it to dry before applying sealer.

Detergent
Bucket
Wire brush
Sponge or mop
Paint-stirring stick
Stiff paintbrush
Long-nap paint roller

Instructions

- 1
  Mix 1/2 cup household detergent for each one gallon of water in a bucket and scrub the surface with a wire brush to remove any loose particles of mortar, dust or grease. Rinse the surface thoroughly with plain water, using a sponge or mop.
- 2
  Mix powdered masonry sealer in a bucket with water according to the directions on the label, stirring it well with a paint-stirring stick until it's thoroughly blended. Pre-mixed masonry sealer doesn't need water added, but stir it so it's mixed well. If directions specify to apply the sealer while the surface is wet, proceed immediately after rinsing the surface or wet it again if necessary.
- 3
  Spread the masonry sealer thickly on the surface with a stiff paintbrush, working it well into the rough surface of concrete and any mortar joints. If you're covering a larger area that's reasonably smooth, use a long-nap paint roller to speed application. Let the first coat dry.
- 4
  Apply a second coat of sealer the same way.

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