Authentic Mid-Century style building materials and DIY kits for your home.

What Floor Should I Choose? (Part 8 – Slate Tile)

April 24, 2024

Slate is a naturally occurring material and has been used in housing for millennia. Even with the age of such a material, it is still a wonderful flooring product for your mid-century home.

History

 

Stone flooring has been used since prehistoric times. There are three types of rock - sedimentary, igneous, and metamorphic. Slate is a metamorphic rock formed from the original sedimentary rock shale, transformed through heat and pressure. Slate is formed in foliated flakes, meaning that large, thin sheets can be chipped off large formations, unlike other metamorphic stones that are monolithic.

Slate can be found in many areas throughout the world: the British Isles, Spain, Australia, Morocco, and Brazil, to name a few. Slate in the United States can be primarily found in Virginia, Pennsylvania, New York, and, arguably, the most well-known slate, Vermont, which comes in multiple natural colors. Vermont slate quarries grew quickly in the mid-1800s with immigrants arriving from Wales who possessed an impressive knowledge of slate mining from years in Welsh slate quarries. Vermont contains what is known as the Slate Belt, an area along the western border abutting New York in an area about six miles wide by 24 miles long. Slate is still quarried here today.

Slate became a great option in mid-century homes, particularly for entryways. However, it was also found in living rooms, on three-season porches, hearths, and other areas. These marketing brochures from the Vermont Structural Slate Co. and the Structural Slate Co. are both from 1957. (Click on each image to read on the Building Technology Library of the Internet Archive.)

Check out this postcard from the collection of the Slate Valley Museum - it's a hoot!

Postcard Scan

Types

There are no different types of slate per se, but there are different colors and finishes.

Finish: Slate is rough-quarried and then finished into the shape and style needed for the application. The first type of finish is the backing of the slate; is it gauged or ungauged? Ungauged tile is in its most natural form, with irregularities of the bottom surface, and is most often used in exterior applications such as patios. Gauged slate is where the bottom of the slate is finished and honed to a flat surface, which is exactly the finish for interior slate tile. The top of a tile for interior use may have many different finishes: cleft (natural), tumbled, honed, and polished. Cleft is the natural state of the stone when cut, with sharp edges and irregular shapes and thickness. Tumbled takes the natural stone and creates regular shapes and sizes, providing a more regular thickness but leaving chipped edges. Honed tile has a regular size and shape and is worked into an even face with rectilinear, regular edges. Last, polished has all the hallmarks of honed but is ground with finer and finer materials to create a completely smooth face. Mid-century homes would characteristically have either cleft or tumbled faces.

Cleft Slate 03

Cleft tile

Tumbled Slate 03

Tumbled tile

Color: Colors and mottling in natural slate vary greatly. Some colors are very monolithic, while others have multiple colors and striations, making them more akin to marble. Color ranges from what we typically think of as slate gray to reds, greens, browns, and even purples and golds.

Colors03

Installation

Installing a slate floor is much like installing ceramic or porcelain tile. However, flooring prep is even more important with slate. Given that it is a natural stone with running rifts, any imperfections to the subfloor surface can cause cracking in the slate tile over time. Installing a dead flat cement backer board is the most important step, along with copious and frequent vacuuming and sweeping as the tile installation proceeds.

Slate tile is installed in mastic made for stone applied with a 1/4", 3/8" or 1/2" notched trowel (dependent on slab size). If you are using a tumbled tile with a more specific shape, you should first find a center point in your room to work from and strike an X and Y axis using a chalk line. With a cleft tile, you may want to lay out your floor before adhering any of the stone to the underlayment to find the right layout for your space. With either tumbled or cleft, the edges will not be perfect, so using tile spacers may not be useful or wanted. Instead, you may need to use just your eye to lay the tile.

Cutting slate can be easily accomplished with a wet saw or, for the more ambitious, with a slate hammer. A slate hammer has a pointed claw that can be used to slowly chip away the edge of a tile to achieve the size and shape needed. If cutting slate with a wet saw, you may still want to have a slate hammer or similar for decoratively chipping edges to give the tile a natural look. When working with slate, you'll definitely want to order overage to account for breakage while installing, cutting, or finishing.

Grout lines will vary by the size of the tile, but you may find it useful to use a larger spacing to allow for tile edge variations. Grout can be sanded or unsanded. Working the grout into the lines will also inherently work the grout into any cracks and crevices in your tile. Cleaning after grouting can be a tedious task but well worth it for a beautiful floor. One tip some use is to seal tile before grouting. Regardless of whether it is done before or after grouting, a sealer should be applied. Sealers come in anything from matte to high gloss. You may want to sample a few on a spare piece of slate before deciding on your favorite.

Where to Buy

Slate tile can be found locally but is often imported from other areas of the country (or world), such as granite or marble. For those local to the northeast, you may be able to purchase specific tiles directly from a quarry. We're showing a few national contacts, but you may want to call local stone companies, too.

Camara Slate

Sheldon Slate Products

Hilltop Slate

Sheldon Slate Products Company, Inc.

Want to learn more about slate in the United States? Check out the Slate Valley Museum on its website here.

Do you have slate floors? We'd love to hear from you.

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Image Credits:

Slate Quarry and Mills, Fair Haven, VT. CC0.
Vermont Slate. Vermont Structural State Co. catalog uploaded by the Internet Archive. CC0.
500 Years in the Making. Structural State Co. catalog uploaded by the Internet Archive. CC0.
Postcard advertising Tatko Flagstone and Flooring 1977. From the Slate Valley Museum Online Collection. Used with permission.
Cleft stone image from Zillow. Listing agent Rachel L. Pitts of Four Seasons Sotheby's. Fair Use.
Tumbled stone image from Philadelphia Magazine. Listing agent Chris Preston of Kurfiss Sotheby's Int'l Realty. Fair Use.
First nine color images by Sheldon Slate Products. Fair use.
Last three colors in a column by Bedrosians Tile & Stone. Fair use.
Tile installation image by Avente Tile. Fair use.
Images of products by the individual manufacturers. Fair use.

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