Tips for applying ceramic tile to concrete
Dear Angie: I'm putting ceramic tile flooring in my kitchen and live on a 10-year-old, ground-level concrete slab. Do I need to put any type of underlayment or vapor barrier underneath it? – Susan K., Acton, Ind.
Dear Susan: It's perfectly acceptable to put tile directly on concrete – with a couple of caveats. First, it is important to determine if there is moisture coming up from the slab. You can test for moisture by taping all four sides of 18-by-18-inch polyurethane plastic on the slab. Be sure to maintain a consistent temperature and do this in an area with no sunlight. Wait 72 hours. If you find moisture under the wrap, seek professional advice.
If you don't have a moisture issue, but have some smaller cracks on the slab (less than 1/8th of an inch), you can use a high quality modified thinset (the mortar used to attach the tile) that has some crack isolation components to it. For larger cracks, use a crack isolation membrane.
Those products should help prevent any cracks in the slab from damaging the newly installed tile. Not only will the membrane protect against cracking, it also serves as a vapor management system and protects the substrate from moisture penetration.
Before laying your new floor, make sure the slab is clean. There are scraping tools (not to mention a little elbow grease) that can help remove any old adhesives or materials, without the need for chemicals. Once you've removed all of that, sweep up any debris, mop, and allow the floor to thoroughly dry.
Sometimes flooring projects can quickly become difficult with cracks, transitions and complex cuts. Consider bringing in a professional to help ensure you get the results you want. Many installers allow you to pick the floor you want and will install it for less than you might think.