QUESTION

How do I repair Cracks in Tile? - Tiles are cracked for the 2nd time in the bathroom. The concrete below is cracked. Other tiles are cracking more and more in the house. Need to know what to do to prevent and repair damage.

ANSWER

ANSWER - If there are cracks in the concrete substrate to which your tile is attached and after replacing the tile they cracked again, and you have other tiles cracking throughout the house then either the cracks are structural in nature (move vertically) or are shrinkage cracks that move within the horizontal plane for the concrete slab.

Tile should not crack if installed correctly.  Tile should not be installed over a concrete floor that has cracks without repairing them or isolating them first.  If you have structural cracks that is normally due to settling within the ground for on-grade slabs or due to too much deflection in suspended slabs, then the cracks and the conditions that caused them have to repaired according to a structural engineer.

If the cracks are common shrinkage cracks then those cracks have to be isolated with a crack isolation membrane.  This is normally a sheet, liquid or trowel able membrane designed for tile installations.  You can isolate an individual crack by applying it over the crack the span of approximately 3 times the within the tile you are using so the tile is completely bonded to the membrane that is bridging the crack.  To prevent future cracking or to isolate large areas of cracking then the crack isolation membrane should cover the entire area.

For your situation, assuming they are shrinkage cracks that were never isolated, and there are a limited number of cracked tiles, I would replace those cracked tiles and apply the crack isolation membrane under the entire tile that you replace.  For a list of manufacturers who produce crack isolation membranes and other tile installation products, go to our website at www.CTaSC.com and go to the resource and links page and to installation products for a list of manufacturers with links to their websites.  Good luck.