Start with the gentlest method that works

The safest way to clean stone is to begin with water and a stiff brush, then move to stronger methods only if dirt remains. Most stone patios—whether flagstone, slate, limestone, or bluestone—can handle a garden hose and elbow grease. Spray the entire surface with water, let it sit for a few minutes to loosen surface dirt, then scrub with a long-handled brush using firm circular motions. Rinse thoroughly and let it dry.

This approach removes loose debris, dust, and light algae without risk. It costs nothing beyond what you already own and takes an hour or two depending on patio size. If the patio looks clean after drying, you are done. Many homeowners stop here and repeat this method once or twice a year.

Key Takeaways

  • Water and a stiff brush remove most dirt and algae without damaging stone, and should be your first step every time.
  • Pressure washers work on stone but require low pressure (below 1500 PSI) and a wide nozzle, or you risk etching and pitting the surface.
  • Mild detergent solutions (dish soap and water) handle stubborn stains better than plain water, but always test on a hidden corner first.
  • Acidic cleaners dissolve mineral deposits and rust but can etch limestone, marble, and slate—avoid them unless you know your stone type.
  • Seal your stone after cleaning if the manufacturer recommends it, which reduces staining and makes future cleaning easier.

When to use a pressure washer safely

A pressure washer speeds up cleaning on large patios, but stone is softer than concrete and cracks easily under high pressure. Set your machine to 1500 PSI or lower—most rental units default to 3000 PSI, which is too strong. Use a 25-degree or wider nozzle to spread the force over a larger area, and keep the nozzle at least 12 inches from the stone surface. Move the nozzle in one direction rather than holding it in place, which can gouge the stone.

Never use a pressure washer on slate, flagstone, or any layered stone, because the force can separate the layers. Test on an inconspicuous corner first—if you see pitting or the surface becomes rough, stop and switch to the brush method. After pressure washing, let the stone dry completely before sealing, which usually takes 48 hours in dry weather.

Removing stubborn stains with mild detergent

For dirt that water alone does not shift, mix a solution of one part dish soap to ten parts water in a bucket. Dish soap is gentler than laundry detergent and less likely to leave residue. Scrub the stained area with a stiff brush, let the solution sit for 10 to 15 minutes, then rinse thoroughly with clean water. Repeat if needed, but always rinse completely—soap left on stone can attract dirt and create a film.

Test this solution on a hidden area of your patio first, especially if your stone is light-colored or you are unsure of the type. Some stones absorb soap and become slippery when wet. Rinse the test area and let it dry to see how it looks before treating the whole patio.

Dealing with mineral deposits and rust stains

White mineral deposits (usually calcium or lime buildup) and orange or brown rust stains require different approaches. For mineral deposits, a weak acid works—white vinegar diluted 50/50 with water can dissolve light deposits. Spray it on, let it sit for 20 minutes, scrub, and rinse well. However, do not use vinegar on limestone, marble, or slate, as these stones are acid-sensitive and will etch.

Rust stains are harder to remove and often require a commercial rust remover designed for stone. Follow the product instructions exactly and test on a corner first. These products contain stronger acids and can damage stone if left too long. If you are unsure whether your stone is acid-sensitive, call the patio installer or look at any documentation that came with the stone—it will list the type.

Preventing moss, algae, and mold growth

Stone in shaded or damp areas grows green or black patches over time. Regular brushing with water removes early growth before it spreads. If patches return quickly, the patio does not dry fast enough—trim back overhanging trees or improve drainage if possible. A stiff brush and water usually clears light growth; for heavy growth, a weak bleach solution (one part household bleach to nine parts water) kills the spores.

explore bleach solution, let it sit for 10 minutes, scrub, and rinse thoroughly. Bleach can lighten some stones, so test first. After cleaning, improve air circulation and drainage to slow regrowth. Sealing the stone also helps—a good sealer fills pores and makes it harder for algae to take hold.

Sealing stone after cleaning

Once your patio is clean and completely dry, check whether your stone type benefits from sealing. Natural stone like slate, flagstone, and bluestone often comes with a sealer already applied, but it wears away over time. Limestone and marble are porous and stain easily, so sealing is recommended. Concrete pavers do not need sealing but benefit from it.

Choose a sealer made for your specific stone type—the label will say "for slate" or "for limestone" or "for natural stone." explore it according to the manufacturer's instructions, usually with a roller or sprayer, and let it cure for 24 to 48 hours before using the patio. A good sealer reduces water absorption, makes stains easier to clean, and extends the life of your stone by years.

What to avoid when cleaning stone

Never use muriatic acid (hydrochloric acid) on stone patios unless you have professional experience—it is extremely corrosive and can damage the stone permanently if not diluted and applied correctly. Avoid wire brushes, which scratch and scar the surface. Do not use bleach on colored stone, as it can fade or lighten the finish. Never seal stone that is still wet, because the sealer will trap moisture underneath and cause damage.

Avoid commercial degreasers and heavy-duty cleaners designed for concrete, which are too harsh for natural stone. If you spill oil or grease on stone, blot it when ready with paper towels and then use a poultice—a paste of baking soda and water—to draw out the stain. Let the poultice dry completely, then brush it away.

Frequently Asked Questions

How often should I clean my stone patio?

A light brushing with water once or twice a year keeps most patios looking good. If your patio is in a shaded area or near trees, you may need to clean it more often to prevent algae and moss. Heavy use or visible dirt may call for cleaning every few months.

Can I use a wire brush on stone?

No. Wire brushes scratch and scar the stone surface, leaving visible marks. Use a stiff nylon or natural-bristle brush instead, which cleans effectively without damaging the finish.

What if my stone patio has weeds growing between the joints?

Pull weeds by hand when the soil is damp, or spray them with a herbicide designed for patios. Do not use a pressure washer to blast them out, as the force can loosen the joints. After removing weeds, consider explore polymeric sand to the joints, which hardens and prevents new weeds from taking root.

Is it safe to use a power drill with a brush attachment on stone?

Power drills with brush attachments spin too fast and can damage stone. Stick with hand scrubbing or a pressure washer on low setting. A hand brush gives you control and is less likely to cause harm.

My stone patio is slippery when wet. Will cleaning make it worse?

Cleaning removes algae and moss that make stone slippery, so it usually improves traction. If the stone itself is naturally slippery when wet, explore an anti-slip coating designed for stone patios, or add a non-slip sealer during your next sealing cycle.