Slate tiles are a sturdy flooring material inside your home, but their durability and natural texture and colors make them useful as a material for exterior floors as well. Slate hides dirt and dust, while other materials might show even the slightest footprint. As long as it’s properly sealed, slate tile can last for years on your patio or porch floor.
Slate Tile Properties
Slate is a very dense but soft stone with low porosity. It is a metamorphic rock composed primarily of grains of mica and quartz, with small amounts of other minerals such as chlorite and hematite, which add color. Most slate tile is gray to black due to the carbon and graphite content, but you can find tiles with red (from hematite) or green (from chlorite).
Texture and Durability
Slate has an uneven, slip-resistant surface. When wet, it is less likely to cause falls than porcelain or other natural stones such as marble. Slate has a hardness rating of 6 on the Mohs scale, which is based on resistance to scratching. Diamond, the hardest surface, is rated 10, while talc, at 1, is the softest. Because of its moderate hardness, slate is not impervious to scratches. While it has a low to medium absorption of oils and other liquids, you should seal slate tiles with a penetrating sealer when used outdoors to protect them from oils, stains and moisture.
General Care and Cleaning
You should clean up spills on slate tile immediately to prevent stains, and place outdoor mats under heavy furniture or metallic pieces to prevent scratches. Use a natural stone cleaning product, which you can find at flooring stores or stone suppliers. Never use acid-based cleaners, such as bathroom cleaners, or acidic products, such as vinegar; abrasive cleaners, such as scouring powders; or cleaners that contain bleach or ammonia. To clean grease, oil, dirt or water stains, use warm or hot water with the stone cleaner and scrub the tiles with a stiff-bristle push broom, then rinse thoroughly with clean water. Mop or sponge the tiles to remove standing water.
Sealing Exterior Slate Floors
As with all natural stone, you should seal slate to prevent staining and to block moisture. Use a penetrating natural stone sealer, which you can find at most flooring stores or natural stone suppliers. Do not use high-gloss or film-forming sealers, which lock moisture beneath the surface of the stone and may make it slippery. Clean the slate before sealing and apply an even coat of sealer using a roller or brush. Typically you should leave the sealer on for about 30 minutes to penetrate the stone, then mop up the excess. These instructions may vary depending on the manufacturer, so read the sealer label before applying. Seal exterior slate tiles every one to three years, depending on the level of use. For tile laid on an uncovered porch floor, the sealer may wear away more rapidly because of rain and sunshine than tile protected by a roof.