QUESTION

We live in a 1963 slab ranch home in the Midwest where the temps are frigid in winter. We are replacing our tile and some carpet with tile. We decided tile would be best because we have had some water issues (broken water softener and water heater and burst radiant heat pipe) and have had to tear out carpet twice now. The radiant heat is no longer functioning. My question is should we use an uncoupling membrane under the new tile? Also is there a way other than a heat mat so that the tile isn’t so cold? This is my biggest concern as our current tile is very cold in winter and we will be replacing carpet in our dining room with tile. The dining and living room are open to one another. Any help or suggestions you can offer would be much appreciated. Thank you!!!

ANSWER

ANSWER - Using an uncoupling membrane will not make the tile installation waterproof, unless you use a special type that can be installed in a waterproof method, and it doesn't really add any value if another pipe breaks.

I don't think the uncoupling membrane would be very effective for floor warming as it will limit the efficiency of a floor warming system.  Normally an uncoupling membrane is used over young concrete to mitigate shrinkage or over a concrete slab with extensive cracking.

There are electrical floor warming systems that can be installed within the thin-set mortar as you install the tile that are much more cost effective than a more effective radiant heating system using hot water to warm the tile and the underlying concrete slab.

It would be recommended to install a liquid or cementitious applied waterproof membrane over the concrete slab and run it up the wall at least 6 inches.  Then install the tile over the membrane.  This will help contain the water and help prevent the collateral damage to the interiors of walls.