HI TIM: So glad I found you.We bought a new home 4 years ago in Vegas. I wanted marble. We have 1200 sq. ft. of marble downstairs. We recently noticed tons and tons of cracking on the marble. The marble cracks are all over, different directions, all rooms. Some are very long. A builder is coming out in 2 weeks to check them out. I spoke with the contracting company who layed the marble and was told they used thin set. Could it be the foundation? This job cost us over $25,000. Who should be responsible to take care of this? We see new cracks starting as well. The existing cracks are not small either. Can you give me some advise on this? Also is there a marble cleaner that would help clean my marble flooring and grout? Thanks so much. - Linda, Las Vegas, NV
DEAR LINDA: If I could come to your home, I'll bet I'd discover that the cracks in the marble are directly over cracks in the concrete slab.
In Las Vegas, your builders pour concrete on the dry soil that's really gravel. If they didn't put in reinforcing steel or use fibers in the concrete, the concrete can develop significant cracks that pull apart. Had they used steel or fibers, the cracks would be hairline in nature.
I'm sure your slab has shrinkage cracks. Concrete shrinks as it cures. It can lose 1/16th of an inch in length for every 10 linear feet.
The marble then cracked because it was locked to the slab with the thinset.
The marble setter should have put a crack isolation membrane down on top of the slab. That way the slab could crack and the marble would have floated over the slab. What a shame!
I recommend that you now just grout the cracks with a grout that matches the color of the marble or is actually a color of the veining in the marble. This way the cracks will appear as if they are part of the marble. It may take repeated grouting to ensure the cracks all get filled. Done correctly, a visitor to your home will never know that the marble's cracked.
You can fix the unsightly cracks in the marble by just regrouting. It's not as hard as you think and I have a four-part set of videos that shows you how you might do this yourself. Here are the links, in order, to the four videos: