The Tile Council of North America includes a few different methods for installing tile with radiant heating. Essentially, the installation method changes based upon whether you're installing electric or hydronic systems as well as the type of structure you're working on. For this article, we're going to go over installation in an uncoupling membrane.
Electric Heating in an Uncoupling MembraneThe most important component of any installation is to read and carefully follow maunfacturer instructions, especially of the heating elements onto the membrane. As the CTEF points out, "some manufacturers make versions of their membrane that allows for electrical heating wires to be applied onto the membrane before tile is installed."
Step 1: Choosing The Thinset MortarThis step is really handled for you because ultimately you should choose an unmodified or modified thinset mortar based upon the manufacturer's instructions. While many of us have been installing tile and more for many, many years and we may be used to know the right material for the job, it is always bestto check what the manufacturer requires. This is especially important because it can affect the system warranty. You read that right, simply using the wrong thinset mortar could void the warranty - neither you or your customers want that. The CTEF recommends, "what the TCNA Handbook recommends in the Materials section of Methods F128, F147 and F148 for installing uncoupling membranes that meet ANSI A118.12 standards."
Step 2: Ensure the Substrate Meets the Industry Standard for FlatnessHere are the standard requirements according to CTEF:
- 1/4” in 10’ for tiles with all sides less than 15” long
- 1/8” in 10’ for tiles with one side 15” or longer
- Grind the high spots (be certain to follow OSHA requirements for silica dust containment)
- Fill the low spots with appropriate rapid setting patch material
- Install a mortar bed
- Install a liquid primer and self-leveling underlayment"
Step 3: Install the MembraneOnce the substrate is flat and you've got your mortar that was recommended by the manufacturer. Next is the actual installation. A couple of quick starting checkpoints:
- Are the perimeter movement joints appropriate? We must keep the uncoupling membrane a consistent 1/4" away from any obstacle or change in plane.
- Are there no bond breakers on the subfloor? Make sure there is no dirt, dust, or other materials that could prevent the mortar from properly bonding the membrane to the subfloor.
Step 4: Install the Heating ElementAs the CTEF states, "every wire manufacturer has some specific instructions describing how to place their wire in their uncoupling membrane system. For instance,
- They will tell you how far apart to place the rows of wire, how close to or how far from the wall the wire should be, etc.
- They tell you how to test the wire before you get it off the roll.
- Some require a couple of simple electrical checks.
- You need to know where the thermostat is or will be and if you have enough lead wire to get to it.
- You need to know where the temperature sensing probe for the thermostat will be placed.
- You need to remember to install the temperature sensing probe so the system works."
- The location of the temperature sensing probes
- The location of the thermostat lead wires and temperature sensing probe wires
- The spacing and distance of the wires from each other
- The distance of the wires from obstacles like walls and toilets and heat registers and vanities
- Any other pictures you think you need to document your wire installation"