Whether you have flagstone flooring inside your home or outdoors, it can require deep cleaning. Most of the time, plain water and elbow grease are more than enough to get your flagstone back to pristine condition. Sometimes, however, you will need a little more cleaning power. Because flagstone is porous, standard floor or all-purpose cleaners are not the best choice. To keep your flagstone in good condition for many years, use simple cleaning methods such as plain water first and then work up to stronger solutions. Stickier residues can be more difficult to remove, so repeat the process as often as necessary.
Sweep or vacuum the flagstone to remove any loose dirt. If you vacuum, use the wand and floor attachments instead of the beater bar because it can scratch the flagstone.
Mix one part bleach with nine parts water in a bucket.
Dip a soft-bristled brush into the bleach solution and lightly scrub at any residue on your flagstone. Pay particular attention to the more heavily stained areas.
Rinse the area well with fresh water and a soft cloth. If any residue remains, repeat scrubbing the area lightly with the bleach solution.
Blot any remaining water with a soft towel. If your flagstone has absorbed more than a few ounces of water, it will appear slightly darker than the surrounding area until it dries completely.
Seal your flagstone to protect it. Use a sealer designed for flagstone. Vacuum or sweep your flagstone often to remove loose dirt that can scratch the surface of the tiles.
Do not use abrasive cleaners on your flagstone. Also avoid using acidic cleansers and ammonia-based cleansers.