Everything You Need to Know About Slate Flooring Tiles

Dirty hiking boots on slate kitchen floor

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Gauged Grade-A quality: $3-8 per square foot.

Ungauged or off-grade quality: $1.50 to $6

Quality matters: If you purchase slate at a bargain basement price then you may be getting B or C grade rated material. This will often be inconsistent in color, size, and even shape, and tiles may have cracks or broken edges. Inexpensive materials may also be a sign of ecologically heedless quarrying or poor social justice practices by mining companies.

Installation: Hiring a contractor to professionally install a slate floor can cost almost three times as much as the material itself. When negotiating a price, make sure to find out if the quote includes pre-installation prep work, materials, adhesives, post-installation protective sealing treatment, cleanup, and removal of waste, in addition to the work of tiling itself.

The cost of hiring a professional may seem daunting, but tiling a floor can be a difficult task. The actual work is not that complicated, but stone tends to be very heavy, so the process of moving it from place to place, and setting each tile in position can be grueling. If you do it yourself and are not familiar with the process you also run the risk of making a mistake and ruining the job, which could cost you in replacement materials.

Slate Flooring Textures

Gauged slate tiles: Almost all slate tiles have their backs flattened out during the refinement process. A straight surface, as opposed to the bumpy irregular face of natural slate, helps the tile back to bond more completely with the grout during installation. In some cases the backs of these materials are also scored slightly, creating even rows that can grip at the adhesive bedding even better.

The few ungauged slate tiles that are manufactured for sale on the market are often used in outdoor locations, where they can be embedded into ground soil to act as stepping stones in gardens and backyards.

Clefted natural slate tiles: While the backs are gauged smooth, the top showing surface of slate is often left largely unrefined, with the natural cracks, clefts, and bristles of the stone showing. This makes for a powerful, rugged look, that mimics the feel of the mountains which the material formed within. It also creates a surface that has great traction, even when it gets wet. With low-quality materials, you may get too much clefting making some pieces nonfunctional.

Honed slate tiles: Honing is a process where the material is polished down until it has a smooth, even surface. Some slates will be able to take a higher hone than others, though few can get to the fully polished state that you often see with marble. The result is a precise look, as well as a floor that is even, without any of the dimensional qualities which can make walking barefoot uncomfortable.

One of the major drawbacks to the honing process is that the colors in the stone tend to lose some of the luster and vibrancy which they have in their original natural state. These floors are also more slippery when wet, though they still usually have decent traction. At the same time, the honing process creates tiles which show both stains and scratches more readily, especially with lighter, and solid color materials.

Color Options

There are literally hundreds of different slate colors available from different producers and vendors. Colors tend to run in veins and can vary over time, so get samples of the material beforehand and check with your retailer to see if they will accept returns on pieces that don’t match. You should also buy at least one extra box of the slate and store it after the installation, so you always have matched material available in case you need to make repairs.

  • Solid-color slate flooring: The uniformity of hue can vary to differing degrees in different types of solid color slate flooring. Some materials will be a single color, with very little changing from piece to piece. Others will have slight variations within the surface, with shades and shadows clouding across the consistency of the tile’s surface.
  • Multicolor: There are a variety of slate materials that contain two or more colors which combine and contrast across their surfaces. The look of the tile and the patterns that are found within it are based on where the various elements that made the stone were located when it formed. Each color indicates the presence of a different material, all of which combined under pressure to create the piece you see.
  • Color note: The presence of red usually indicates that the material contains iron. When it does, that makes red slate flooring inappropriate for outdoor applications, as rain can oxidize that element, causing it to break down the same way it would rust a piece of iron. 

Most Common Tile Sizes

  • 12x12

Slabs and larger sizes not usually used in flooring.

All tiles can also be cut down into smaller squares, rectangles, or in some cases triangles. Cuts should be done to a size that evenly divides the material so that there is no waste. Cutting 8” squares from a 16” tile uses the entire piece, where 7” squares would leave you with waste. 


Slate flooring needs to be treated with a penetrating below surface chemical sealer, and a barrier sealer, during installation before grout is applied. This is done to protect the porous tiles from stains. It should then be treated with these sealing agents again at least once immediately after the installation is complete. After that, an annual application is usually enough to keep the floor mostly stain free. More frequent sealing will give the material a glistening sheen.

Once slate is protected with the proper chemical sealants, it is fairly easy to maintain. Spills should be wiped up immediately, and for regular cleaning, you can just sweep, vacuum, or mop the floor periodically. If you mop it use either warm water on its own or mixed with appropriate stone soap. Never use any acidic or abrasive cleansers on a natural stone floor as they will cause a chemical stain reaction.

Grout: This is the most vulnerable point in a tile floor installation. Grout is used to buffer the space between tiles, giving them a yielding cushion against which to expand and contract when the temperature rises or falls. They are also very porous and can suffer from stains, water penetration, and mold if not sealed regularly. If problems arise with grout lines, it is always possible to remove them and replace them with new grout.
Repairs: In tile form slate pieces that become damaged can be removed and replaced. This process involves cracking and digging the tile out of its installation bed, being careful not to damage surrounding pieces. Once the subfloor is scraped free then a new tile can be installed and grouted into its place. Make sure to seal the new tile and the grout around it once the adhesive is dry.