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How to Clean & Seal a Stone Wall

Sal Marco

Stone walls add interest to gardens, patios or indoor living spaces. Sealing a stone wall preserves the wall, allows rainwater to run off and makes future cleaning easier. Masons and homeowners have a variety of stone to choose from when erecting a wall, including brick, field stone, flagstone or river stone.

Protect stone walls from damage.

Cleaning and sealing methods remain the same regardless of the type of stone.

  1. Wash the wall with a mild detergent and a scrub brush. Scrub off areas of moss, algae or mold growth with an equal mixture of chlorine bleach and warm water. Rinse the wall thoroughly and allow it to dry completely. Use a power washer at a low setting for large outdoor walls. Use care around grout or mortar lines to avoid damaging the joints.

  2. Repair cracked or loose mortar joints. Hold a masonry cold chisel at a 45-degree angle to the damaged mortar joint and strike with a hammer to remove the damage. Mix mortar with water to develop a paste-like consistency. Fill a grout bag with mortar and squeeze grout along void joints. Allow the mortar to set for 48 to 72 hours before sealing.

  3. Apply masonry stone sealer to the mortar joints and deep recesses with a paintbrush. Allow the sealer to dry -- usually two to four hours.

  4. Roll two to three coats of masonry stone sealer with a paint roller over the entire wall. Allow each coat to dry for two to four hours between applications.

  5. Tip

    Wear a dust mask, safety glasses and gloves when making repairs. Only seal dry walls. Sealer will not adhere properly to wet or damp stone.