Slate Flooring

Slate flooring’s natural good looks and versatility allows it to be used in many areas throughout the home. It has a less formal appearance than marble or granite. It can create a mood that can be rustic and informal or well-groomed and modern. Slate flooring is exceptionally durable, slip resistant and stain resistant.

The true sophistication of slate flooring is in its natural colors, from solid hues like black, gray, purple, red and green to freckled and mixed tones. The unique colors result from the presence of different natural minerals, such as graphite (blacks), chlorite (greens), and hematite (reds).

Slate is a very fine-grained metamorphic rock cleaved from sedimentary rock shale. One of the characteristics of slate is that this cleavage allows the rock to be split easily into relatively thin tiles. The color and uneven pattern of the natural cleft gives each tile a distinctiveness that, when arranged with other tiles in an expansive surface, achieves a unique appearance.

In heavy traffic areas, honed black slate flooring does have a tendency to show the natural scuffing of shoes, and the scratches give black slate flooring a slightly grayish appearance. All natural stones will eventually show the scuffing and, therefore, highly polished stones should be avoided for flooring.

Different finishes are available in slate, as in other stones. The finishes are described as follows:

• Natural cleft. The natural split or cleaved face. It is moderately rough with some textural variations. Thickness will have a plus or minus tolerance of 1/8 of an inch.
• Sand-rubbed. This has a slight grain or stipple in an even plane. No natural cleft texture remains. Finish is equivalent 60-grit and is obtained by wet sand on a rubbing bed.
• Honed. This finish is equivalent to approximately 120-grit in smoothness. It is semipolished, without excessive sheen.

You can buy slate flooring in rectangular and square sizes that range from about 1/2 to 1 inch thick and in sizes from 6 by 6 inches to 24 by 24 inches. Slate flooring is either gauged or ungauged. Gauged slate is processed through a grinding machine, usually to smooth out one side, leaving the other (cleft) side unfinished. The machine finish insures a uniform thickness for easy installation. Ungauged tiles are uneven on both sides, vary in thickness, and are best used for patios and walkways.

There are, however, several points to remember with both types of installation. If grout is used with slate flooring (the spacing varies from ¼ to ½ of an inch), it is important that any excess be cleared off, because grout that has dried on the slate surface will probably never come off. If grout is not used, the slate tiles are butted against each other. Joint lines are staggered so no lines are more than 2 to 3 feet in a straight line.

Thick-bed installation is similar to flagstone. All joints should be ½ inch wide flush joints and should be pointed with 1:2 cement-mix the same day the floor is laid to make joints and setting bed monolithic.

A slate floor is easily maintained with mold soap and water. While waxing is not harmful, it detracts from the natural beauty of the stone, turns the floor darker shade, and may yellow the grout.