How to Wash Flagstone

Gardeners enjoy utilising flagstones to create pathways, patios, steps or other landscaping ornamental. They provide a natural look in any landscape. Flagstones can also be used for indoor entrance ways, walls or other indoor flooring. Outdoor flagstones can develop mould and accumulate dirt, which makes them appear dull. Indoor flagstones have a protective wax covering or sealant that helps protect them from extreme soiling or footprints. Yearly cleaning of flagstones helps to keep them looking fresh and new.

Clean indoor flagstones by gently wiping down the surface using 50-50 mix of white vinegar and water. Clean outdoor flagstones by hosing them off with a pressurised hose nozzle or a pressure washer.

Remove tough stains on indoor flagstones with a wire brush and indoor masonry cleaner. Add 1 quart of muriatic acid to 2 gallons of water to clean tough outdoor stains. Dip a stiff-bristle brush in the mixture and scrub the stain vigorously. Hose the muriatic acid solution off the flagstone with water.

Apply a mixture of 1 part bleach and 9 parts water to tough indoor and outdoor flagstone stains. Apply to the stain and scrub vigorously with a stiff-bristle brush. Rinse the flagstones with water to remove the bleach and water solution.

Wait 24 hours for the indoor and outdoor flagstones to completely dry. Apply a commercial flagstone sealer across the surface of the flagstones. Follow the directions on the label to apply.


Take care when using muriatic acid and bleach around plant life because it can easily harm or kill plants. Wear protective rubber gloves, old clothes and safety goggles when applying bleach and muriatic acid.

Things You'll Need

  • White vinegar
  • Pressure nozzle or pressure washer
  • Bleach
  • Indoor masonry cleaner
  • Muriatic acid
  • Bristle brush
  • Commercial flagstone sealer
  • Rubber gloves
  • Safety goggles
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About the Author

Based in Oregon, Kimberly Sharpe has been a writer since 2006. She writes for numerous online publications. Her writing has a strong focus on home improvement, gardening, parenting, pets and travel. She has traveled extensively to such places as India and Sri Lanka to widen and enhance her writing and knowledge base.