We had a professional contractor remodel our home 5 years a go. At the time, we had a sunken living room which the contractor filled with concrete in order to bring it to the same level as the rest of the house. We had ceramic tile laid on top of the concrete. Over the years, the grout line has separated where the original concrete meets the new concrete. I have removed the cracked grout line but am not sure what to do to prevent any new grout from cracking in the future. Someone suggested mixing cement grout with caulk. The grout lines are only 1/8". Thanks for your help.
Liz W ~ Orlando, FL
Hi Liz. There will probably always be a little bit of movement where the new concrete slab meets the original concrete in your home. That's one of the reasons why concrete contractors often place an expansion joint between two concrete slabs poured at separate times.
My suggestion would be to mix some flexible grout additive in with your new grout rather than using caulk initially. The additive is latex based and should make the joint a little stronger and allow some movement without cracking. The product should be available at the larger home improvement stores around Orlando and you might also check at tile or flooring retailers.
If you still have a problem with the grout cracking, caulk might be the best solution. I would recommend a mildew resistant silicone that should hold up better in your humid climate. It is the same type of caulk that's used in showers and tubs where the grout can crack due to movement.
You don't mention exactly where this grout joint is located in relation to your home's floor-plan. If the two concrete slabs meet at a doorway or even at an opening of some sort that is narrower than the entire room width, you might try a low-profile wood threshold over the grout joint. You would still have the crack, but it wouldn't be seen. I have used this technique myself on numerous occasions and if you stain the trim to match other trim or furniture in the room, it can be quite attractive.
If you decide to try this solution, use a drill bit designed for ceramic tile to drill down through the wood and tile or the ceramic flooring may crack. You'll need to use fasteners designed for concrete to hold the trim down.