Placing Overlays over Tile Floors
What is the best self-leveling concrete overlay to apply over ceramic or clay tiles? Do the tiles need to be treated before applying the overlay?
This will depend on the type of tiles you are going over. Glazed tiles usually require a light sanding to "rough up" the surface. The glaze can often act as bond breaker and is a difficult surface for anything to adhere to. Porous unglazed clay or stone tiles, on the other hand, require no additional preparation. The other factor to consider is the depth or thickness of the overlay. If you go too thin, the grout lines in the tile floor can ghost through the material. This won't matter if another hard flooring surface will be going over the self leveler, but the ghosting can ruin the appearance of the floor if the self leveler is going to be stained or sealed. If you will be applying the self leveler at thickness less than 1 inch, consider using a crack-suppression membrane or fiber fabric to help eliminate the possibility of ghosting. If the grout lines are deep, use a repair mortar to fill the grout lines and create a level surface.
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Author Chris Sullivan, ConcreteNetwork.com technical expert and vice president of sales and marketing for ChemSystems Inc.