How to Clean & Seal a Flagstone Wall

Read the label on your stone sealant thoroughly. If your flagstone wall is newly constructed, read the label's recommendation for the time that must elapse before sealing new flagstone structures. This may be anywhere from three to 60 days.

Scrub the flagstone wall clean with a scrub brush and the stone cleaner recommended by the sealant. If you do not have access to that product, clean with trisodium phosphate (TSP) powder solution mixed according to the label's instructions (usually 1/2 cup powder per gallon of hot water. Wear gloves when cleaning. Rinse the wall thoroughly with a hose to remove all traces of the cleaner.

Allow the wall to dry for at least 24 hours before applying the sealant.

Paint a generous layer of sealant onto all surfaces of the flagstone wall with a paint brush or paint sprayer. Follow the label's instructions for application methods and amounts. Most manufacturer's recommend applying the sealant early in the morning or late in the afternoon when the sun is waning and temperatures are between 50 and 80 degrees Fahrenheit. Some manufacturers recommend two coats for outdoor protection. When applying the first coat, allow it to dry for the label-recommended amount of time (usually overnight) before applying the second coat.

Rinse your paintbrush with mineral spirits (or the solvent recommended by the manufacturer) followed by water immediately after you have finished applying the sealant. Many sealants contain chemicals that release combustible gases as they dry.