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myowneq 04-15-2013 02:23 PM

Tile Adhesives & Radiant Floor Heater
Hi Everyone,

I'm nearing the completion of my master bath. I am about to start the last major component, the electric floor heater and ceramic tiles.

I was reading the installation guide for the floor heater and came across the tile adhesive section. It says:

"A latex-modified thin-set cement-based mortar and grout is recommended instead of water-based multi-purpose product when installing a radiant product. Do not use solvent based adhesives or pre-mix mortars because they are not heat resistant and do not conduc heat well."

The tiles are 12 x 12. The subfloor is 3/4" plywood topped with cement board. Everything is glued and screwed.

I've seen a lot of recommendations for Marpei products but not sure what product exactly to get.

Someone help please?


JazMan 04-15-2013 08:51 PM

Hi Tim,

Mapei is one of the many fine brands, use any one of them.

Latex-modified mortar and grout is also known as "fortified or enhanced" etc. They are blended with dry latex/polymer, so all you do is add the mortar to water, mix and go. You can also get the same results by using regular dry-set mortar and mixing with an additive instead of water. Same thing.

Modified mortars meet ANSI 118.4 & 188.11, while dry-set meets A118.1.

Just make sure your are not talked into buying anything that is pre-mixed, even if it is called "thin set mortar". Thinset mortar only comes in powder form.

Be sure to plan ahead and follow the manufacturer's directions. Some have you pour self-leveling-cement (SLC), over the warming mat to a specific depth. It also depends on how flat your floor is. Do you know? How did you measure?

BTW, you neglected to add your location in you profile. It might be helpful.


warmsmeallup 04-17-2013 09:07 AM

You wrote:
"because they are not heat resistant and do not conduc heat well."

The two statements don't work together. If a material is NOT heat resistant, by it's nature, it conducts well because it doesn't create resistance. If it is resistant, it creates resistance and the heat isn't transferred well.

We've installed electric radiant heating in 100's of bathrooms with every type of cementous mortar imaginable. No problems.

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