Asked on Jan 26, 2013

Why do Marble floor tiles crack?

by Nevinweeks
Often the natural veining in marble floor tiles proves to be a weak point that can crack and crumble leaving small holes in the tile along a vein. What is the best product with which to fill these holes and hopefully prevent the weakness extending further?
  3 answers
  • KMS Woodworks KMS Woodworks on Jan 26, 2013
    Having installed thousands of sq feet of tile (marble included) a lot if this depends on the "quality" of the tile itself. I have seen some where every tile is reinforced with a fiberglass mess and an epoxy sealer on the back...this helps a lot. Other stone is just marginal to begin with. You will see far more trouble when comparing cheap economy tile (far east import) that has lots of "fill" (this is a stone colored resin that is applied to natural voids in Travertine) Marble is a beautiful stone but its use should be taken into consideration. Floors and kitchen counters are poor choices due to marbles "softness" and staining potential. Acid etching is another issue, marble is a type of limestone which dissolves in acid. Shower walls and backspalshes are a better choice. When I install marble I typically get 20% more material if the stone is of lower quality, pieces of a weak nature are simply not used, experience in "reading" the stone will show you which ones are suspect to fail.
  • The bottom line why tile cracks is movement of the sub floor and poor installation methods. While I would agree with Kevin on the quality playing an important roll in this. you can still put a low cost floor down and if done correctly prevent it from cracking. I will add it is much harder to do a low cost floor as you need to over kill the install to prevent cracks while a better quality floor tile can take a bit of a beating before it cracks. In addition to preventing floor movement you have the application of the floor thinset. Depending upon the size of the tiles being placed and you do not properly back butter the larger tiles and use thinset that has started to dry out you will for sure see cracks due to tile movement. Location of seams on the sub floor is also critical all sub floor seams must be properly fastened down. And if your not using a cement board for your sub floor material, you must use a uncoupling membrane such as Kerti or equivalent. Wood floors expand and contract. If you lay your tile directly on a wooden surface the bond between the thinset and the wood will soon fail. This will result also in a crack in the floor with the seams often telegraphing up to the surface of the tile face. What the uncoupling membrane does is allows wood movement without causing the tile and thinset from failing. Using a tile backer board, cement board also acts in the same manner. The wood moves below the cement board while the cement board expands and contracts at the same rate as the tile and thinset. This movement or difference in movement from the two materials is what prevents the tiles from cracking and coming loose.
  • Hamtil Construction LLC Hamtil Construction LLC on Jan 27, 2013
    Sometimes marble will come from the quarry or fabricator with an epoxy resin filled in some of the veins or cracks to strengthen it. In terms of adding this in an installed environment, I have only seen a mason do it once, and on a column, not a floor tile. I think the key here is the installation, as the others have said. If the substrate is inadequate, there is not much that can be done to the tile itself.