DEAR TIM: Granite tile looks like it would be excellent flooring or a wall treatment. Is granite flooring a good choice or will it scratch easily? I am thinking of installing granite tile in several places, but wonder if I can do it successfully. Can you make different designs with granite tile, and if so, how? How hard is it to install granite tile on floors or walls? Karen S., Mount Laurel, NJ
DEAR KAREN: I'll go on the record right now. You are going to love the granite tile you will be installing. Granted (no pun intended), I am not as objective as I should be since I am a college-trained geologist and granite happens to be my favorite rock. You should be forewarned now. When you visit a real stone supplier that has a full assortment of granite tiles, you will be mesmerized by the colors, patterns, different-sized mineral grains and beauty of the granite.
The stone suppliers I visit stock granite flooring in 12-inch by 12-inch tiles. The tiles are about 3/8 inch in thickness and precision cut so the sizing among different tiles is very uniform. This is an important thing to consider as the finished grout lines will readily call out granite tiles that are too large or too small.
One thing you will notice quickly is that granite tile is very heavy. After all, it is solid rock. You need to take this into consideration if you are installing the granite on walls or some other vertical surface. Gravity will be constantly tugging at the granite tile and if it is not attached securely, it will fall off the wall. In fact, the substrate like cement board or waterproof gypsum board must be expertly attached to the wall studs or the granite can pull it from the wall as well. You can't use too many screws to attach these products to the wall studs.
Granite is a very hard rock. A geologist will tell you that it is an igneous or metamorphic rock that is highly saturated with silica. Silica when combined with oxygen makes the mineral quartz, and it has a hardness of 7 on the Mohs scale. Suffice it to say there are not too many things that will easily scratch granite tile.
I can't think of one place where I wouldn't install granite tile. It can withstand just about all the abuse you can throw at it. It is ideal for exterior applications as many of the early roads in the USA were made from granite cobblestones. I have granite stones in my own driveway and they are unaffected by heavy trucks or freezing weather.
You can successfully install granite. When granite tile is installed on floors, one of the most important things to keep in mind is that the subflooring beneath the granite must be solid with no flex in it. Granite tiles are strong, but as with any stone product, it can crack if it is put under tension. A hollow spot beneath a granite tile or a flexing subfloor can cause the granite flooring to bend and crack. Be sure the floor beneath the granite tile has all low spots filled and any high spots 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 very well to the granite and the wall or floor surface. Consider using a crack-isolation fabric between the granite tiles and any 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.
Use a diamond wet saw to cut the granite tile. In fact, that is just about the only tool you can use unless you want to spend days sawing the granite tile by hand. If you get a powerful diamond wet saw, you can cut the granite tile into any shape you desire. I made an interesting geometric design for my daughter's shower wall using standard granite tile. It takes a while to layout and make the precision cuts, but it is absolutely worth it. These designs look stunning when you use different colored granites to complete the design.
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 incorporating 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. I urge you to use white thinset for lighter-colored granites. Be sure to ask the stone supplier for the exact product to use to secure the granite tile to the floors or wall. Avoid the organic mastic products that look like cake icing. Often these do not have the strength needed 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 on top of one another and the combined weight is hundreds of pounds. If the granite moves as the thinset is curing, it weakens the bond between the wall and the granite significantly.