How to Clean a Flagstone or Bluestone Patio

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Sometimes, simply blowing off the leaves or sweeping the dirt is enough to keep your flagstone or bluestone patio beautiful. Other times, you need a little more cleaning power to scrub away stains, from moss to grease. Hosing down your patio after sweeping away the debris can help you spot the stains easily and help you know where to focus your attention.


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How to Clean Patio Stones

The best time to clean patio stones is on a cool or overcast day to keep the cleaning solution from evaporating quickly. Don't let the cleaning solution dry on the pavers. Cleaning a large patio in sections makes it easier to avoid having the cleaner dry on the stones. The steps to clean patio stones include:


  1. Mix 1 to 4 ounces of a neutral-pH stone cleaner per gallon of water or whatever ratio the manufacturer suggests. For large patios, mix several gallons of the solution in a large bucket.
  2. Mop the solution onto the pavers.
  3. Wait for two minutes before you scrub the pavers, giving the solution time to loosen dirt and stains.
  4. Scrub the pavers with a natural- or plastic-bristle brush. Agitate the brush to loosen dirt and stains.
  5. Spray the solution off the pavers in a sweeping motion using your jet-spray nozzle on your garden hose.
  6. Use a clean mop or wet vacuum cleaner to remove excess water.


How to Remove Biological Stains

Biological stains include things like algae, mildew, and moss that often grow on flagstone patios and other outdoor surfaces. To remove them from your patio stones, the steps include:

  1. Add 1/2 cup of hydrogen peroxide or ammonia to 1 gallon of water to remove biological stains.
  2. Mop the solution onto the affected area and allow it to soak for several minutes.
  3. Scrub the stones with a natural- or plastic-bristle brush.
  4. Rinse the cleaning solution off the pavers with a jet-spray nozzle on your hose. Use a clean mop or wet vacuum cleaner to remove excess water.


Alternatively, you can apply undiluted white vinegar to the biological stains and allow it to sit for a few minutes. Scrub and rinse the pavers to remove the gunk.

How to Use Poultice

Stains are foreign matter absorbed into the stone. Removal of the stain is a reverse process, pulling the foreign matter out of the stone. You can do that with a poultice treatment, which is a cleaning product that you use to make a paste. The steps include:


  1. Put poultice powder in a small, disposable plastic container and add enough distilled water to make a thick, spreadable paste. Stir it with a plastic spoon, carefully following the manufacturer's instructions.
  2. Wet the stained area and 2 to 3 inches beyond the stain with distilled water, then spread the poultice paste 1/4- to 1/2-inch thick on the wet area.
  3. Cover the area with plastic wrap and tape the edges of the plastic to the pavers. Leave the poultice in place for 24 to 48 hours.
  4. Remove the plastic wrap and allow the poultice to dry completely before scraping the poultice material off the flagstones. Rinse the treated area with distilled water and wipe dry with a soft cloth.


Repeat the poultice treatment on the flagstone area if the stain isn't completely removed. Persistent stains may require professional treatment. Consult a local stone professional for advice if you aren't able to remove a stain yourself.


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