JASON PETTINATO TILE HAS BEEN SELECTED AS A PARTICIPANT FOR UPDATING
THE:
2011 TILE (C54) CALIFORNIA STATE EXAM
How To Protect Tile From Cracks in Concrete
Whenever your considering to install tile over concrete, don't be surprised to see cracks in the concrete slab. I use a rule of thumb and tile over cracks 1/8" and smaller using a high quality modified thinset. Anything larger and it's time to consider using a crack isolation membrane. Cracks usually "crown" or create a high spot which may need to be ground down using a grinder and concrete cup wheel. You can use a 6' straight edge or level to see how bad the hump is. Not all cracks need to be ground down but should be checked to see if you need to add extra thinset on the surrounding tiles to help ease the high spot. Crack isolation products come in various forms. Trowel on membranes, slip sheet, peel and stick, and even a thinset that claims to do it all.
It is always better to play it safe and use some type of crack isolation membrane over cracks in concrete even if you may feel that there hasn't been any movement for the last few years or "it's done cracking" because the concrete is 30 years old. Don't fall into that trap of thinking it's done moving. Nobody really knows for sure so assume that it's possible for future movement and now is your chance to protect your new tile. By using a crack isolation membrane and high quality modified thinset over a clean concrete floor, you have now increased the chances of a successful tile installation that you can enjoy for years to come! Here's a thinset guide with more details.
Any cracks larger than 3/8" may need more attention as crack isolation membranes do have limitations. Generally an epoxy is used to fill in the cracks after grinding out the cracks to allow for a better bond. Those large cracks generally need to be ground down due to crowning so use your straight edge to check it out. This is exactly how ceramictilepro approachs possible tile installations over cracks.
