Unfinished natural stone has been used in exterior construction applications dating back millenniums, but ancient builders didn’t have to worry about caring for exterior stone surfaces until the Egyptians started applying fine masonry techniques to their pyramids. Archaeological evidence indicates that the Great Pyramid of Khafre, the one believed to have been adorned with gold plating at the top, was once covered with delicately finished granite and limestone slabs, which likely attracted a lot of dirt and grime just a few years after installation.
Cleaning exterior surfaces made of raw fieldstone or engineered paving bricks is something that can be accomplished with power washers, rugged brooms, and even wire brushes, but this isn’t recommended for finer natural stone such as travertine, marble, granite, flagstone, and bluestone. Essentially, any outdoor application of finished stone will require gentle and frequent care.
Keep Dirt and Water Away
The basics of cleaning exterior stone include sweeping, dusting, and wiping. The idea is to never let dirt, debris, water, or liquid spills sit and accumulate. When sweeping, make sure to start with a horizontal or vertical motion and finish in the opposite direction. If your exterior stone is exposed to rain, you can just let it air dry. If it’s covered, wipe down water spills and excess moisture.
Only Use Natural-Stone Cleaner
Forget about liquid detergent and other solutions sold at your local supermarket. Your exterior stone should be cleaned with a specially formulated granite outdoor stone cleaner. Since outdoor stone surfaces are bound to get dirtier and require scrubbing, you may want to use a half-and-half mixture of cleaner and water.
Protect Your Exterior Stone with Sealant
When highly porous stone such as marble is used in exterior spaces, maintaining a fresh surface seal becomes crucial, and this is the case even if it’s covered by a roof and doesn’t feature a polished finish. Make sure to thoroughly clean the surface before applying granite sealer, which should be reapplied as soon as you notice water drops or puddles leaving dark spots or, preferably, before these issues occur.
Remove Mold and Mildew
Just like on the tiles and countertops in your kitchen and bathrooms, mold colonies can form on your exterior stone, which is why you need to keep it clean and free of dirt, debris, and water. When moisture and dirt mix, mold spores will find enough nutrients to develop and spread. Mold that forms on top of sealed stone isn’t a problem because it can be wiped away. However, mold that penetrates through pores should be removed with a 50/50 solution of bleach and water. Scrubbing mold away from natural stone requires a soft touch from a gentle pad or nylon brush. Remember to clean and seal your outside stone after removing mold.
For more tips on how to clean outdoor stone, reach out to the Stone Care Experts at Granite Gold®. All of our products are safe to use on granite, slate, limestone, and other types of natural-stone and quartz surfaces. Give us a call today at 1-800-475-STONE (7866).
Also, make sure to check out our Facebook page for more handy tips.