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Installing a Heat System Under Tile

This was the first time I used a Flextherm heating system and I'm really impressed. Really easy to install.
Heat System Under Tile

You space the wire in the orange tract to the spacing size you ordered. You can order 2' or 3' spacing as we did. If you have a little too much or too little wire you simply adjust the width of the spacing.

The thermostat and probes bury in the mortar. The connecting ends will go in and up the wall to the controls. You simply start your flex therm installation at the wall where the controls will be.

The strips of wonderboard will act as a level when we float the mortar. The big wonderboard pieces on the left are where cabinets will go so the heat does go under them. I used wonderboard here because it comes 1/4" thick, the thinnest concrete backerboard. Floor height is a issue because the hardwood floors are 3/4" and you want to go as little above that as possible.

The next step is to take a grout float and mix mortar to hold tiles in place for leveling. Hard rubber grout float will not harm the wire, actually the wire helps as you spread mortar down the wire with the float resting on top. Installing the wire and flat troweling mortar to hold it in place took less than a full day. Allow to dry over night.

Everywhere that the heat system doesn't go, wonderboard does.

We used two thermostat probes in case one ever went bad and all the wire and tract is below the wonderboard.

I knew that the long section would be easy to level but even the John room was easy as well. Flextherm wants you to keep the wire away from walls so use concrete board for a guide to leveling.

The wires are set and it's no problem walking on them for leveling, starting in the John and working our way out the door. This is a lot of mixing of Kerabond/Keralastic. You could use a cheaper water-added mortar but I choose not to. K/K is flexible and cleans easier and is the best bond.

We are working two ends against the middle here, but that is the best way out. Simply drag the straight edges, smoothing the mortar into a flat smooth surface. The next day, knock off small burrs with a putty knife.

You might have to drag 2 or 3 times so you leave just the right amount of mortar. Clean straight edge after each use. Barricade doorways so nobody walks in by mistake.

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