Relaxing on an outdoor patio is one of the greatest pleasures of owning a home. But that pleasure can be tinged with worry if the stones on your patio are slippery. Virtually all patio stones can present a hazard, as they inevitably become slippery over time with a coating of algae or moss (moss tends to develop between stones) that develops when the patio is damp with dew or moist from rain. Traces of moss can be invisible and develop without a homeowner's knowing that moss is growing. However, patio stones are easy to clean with a simple bleach and water solution.
Mix 1 cup bleach and 2 gallons of water in a bucket or watering can.
Pour 1 tsp of bleach solution on the underside of one stone and let it dry completely to see if discolouration occurs. If it is not possible to lift your patio stones, choose a stone that is in an out-of-the-way location for testing. If you see discolouration, your bleach solution is too strong and you need to dilute it further with more water.
Pour the bleach solution over your patio stones. Leave it there for two to three minutes.
Scrub your patio stones with a stiff-bristled brush.
Rinse the stones by flushing with a hose. Complete this step thoroughly, because solution left on the stones could cause discolouration.
Repeat Steps 2 to 5 with a stronger solution of bleach and water if necessary. Do not move beyond a 1-to-1 ratio.
Clean your patio stones at least once a year, or whenever they become slippery when wet.
Although a diluted bleach solution is safe for most plants, thoroughly water a lawn or nearby plants that you may have splashed with the solution. This additional water will dilute the bleach even more and prevent any damage to your lawn or plants. Some commercial products contain ferrous sulphate, which may discolour your patio stones. Some contain hydrochloric acid, which can damage your patio stones and nearby plants. Read labels carefully when you buy commercial products.