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Granite tile on floors, walls? It rocks!

By Tim Carter, Special to the Times
Published November 24, 2007


Q: Granite tile looks as if it would be excellent for flooring or a wall treatment. Is granite tile a good choice for flooring or will it scratch easily? Can you make different designs with granite tile, and if so, how? How hard is it to install on floors or walls?

A: If you install granite tile on your floors or walls, you are going to love it. When you visit a real stone supplier - one with a full assortment of granite tiles - the colors, patterns, mineral grains and beauty of the granite will mesmerize you.

The stone suppliers I visit stock granite flooring in tiles 12 inches square. The tiles are about 3/8 inch thick and precision-cut for uniform size. Uniformity is important, as the finished grout lines will readily call out granite tiles that are too large or too small.

Granite tile is very heavy. Remember this if you install granite on walls or some other vertical surface. The granite tile will fall off the wall if it is not attached securely. In fact, the substrate (typically cement board or waterproof gypsum board) must be expertly attached to the wall studs, or the weight of the granite may pull it from the wall too. You can't use too many screws to attach these products to the studs.

Granite is extremely difficult to scratch. It can withstand just about all the abuse you can throw at it. It is ideal for exterior applications (many of the early roads were made from granite cobblestones). The granite stones in my driveway are unaffected by heavy trucks or freezing weather.

You should be able to install granite tile. If you're installing it on floors, make sure that the subflooring is solid, with no flex. Granite tile is strong, but like any stone product it can crack if put under tension. A hollow spot under a granite tile or a flexing subfloor can cause the tileto bend and crack. Be sure all low spots on the floor beneath the granite tile are filled and any high spots are ground down. You want the subfloor to be in the same plane.

I prefer to install granite tile using cement-based thinset mortar. This product is very sticky and will bond well to the granite and the wall or floor surface. Consider using a crack-isolation fabric between the granite tiles and the flooring to prevent cracks in the finished granite. The lines between each granite tile can be grouted with unsanded wall grout if the joints are 1/8 inch or less in width. Joints wider than that should be grouted with sanded grout.

A diamond wet saw is the only tool you can use to cut the granite tile unless you want to spend days cutting by hand. Use different colored granites to create interesting geometric designs with the tile. It takes a while to lay out and make the precision cuts, but it is absolutely worth it.

Granite tile does not come with self-spacing lugs on the edges of the tile. This means you have to space the tile by using your eye or by using plastic spacers as part of the installation. The spacers are easily removed once the thinset mortar has cured.

Thinset mortar comes in two common colors: gray and white. Use white thinset for lighter-colored granites. Ask your stone supplier for the exact product to use to secure the granite tile to the floors or wall, but avoid organic mastic products. Often they don't have the strength to hold granite in place permanently.

When installing granite tile on walls, it must be supported well until the thinset cures. The granite is so heavy, it will slide down the wall. This is especially true as you start to stack pieces vertically and the combined weight is hundreds of pounds. If the granite moves as the thinset is curing, it significantly weakens the bond between the wall and the granite.

Tim Carter is a licensed contractor. To view previous columns or tap into his archive of information and sources of building materials, visit Ask the Builder on the Web at www.askthebuilder.com. You can write to Tim Carter at P.O. Box 36352, Cincinnati, OH 45236-0352.