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Question Regarding Installation of Floor Heat and Tile

October 03, 2014, 07:52:25 pm

I've read through all of the threads here and a few on IRV2 regarding electric heat cable and tiling but it seems most people have had others do the install and really don't know the exact details on how it was done and I'd like to see if there is any consensus on the optimal way to prevent cracking.

My plan is to use heat cable rather than heat mat due to the mat having a larger spacing and subsequently less watts per sq. foot.  2" spacing gives 15-18 watts/ sq. ft while 3"  is about 10 watts/sq. ft.  The heat mats all seem to be the 3" spacing. 

So my main question is if you should use a self leveling mortar to encase the heat cables prior to putting the tile on top of it.  Like this-

Using Edge Strip Kits to Install WARMUP Loose Wire Electric Floor Warming System

I realize that I would need to use something like Laticrete 333 to keep the self leveler flexible but I've also read that some people have just installed the tile right over the top of the cable/mats. 

For anyone who has done this type of install, which method is preferred?

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Re: Question Regarding Installation of Floor Heat and Tile

Reply #1 – October 03, 2014, 08:19:50 pm

Robert, I have done quite a few infloor heating installs under tile but have never done it this way with self leveller cement. I think it is a good way to do it after looking at video if you have never done one before. I use the acrylic thin set cement and apply with trowel and had never a problem or recall, but agree this (video) way is easy and as long as you put the right amount of product all over the area and do not put too much in one place(it will creep ontop of the "guide strips") this will be nice and simple for you.
I agree on using the wire method as the mats only come in certain sizes and you do get cold spots. The heat does not migrate more than 4 or 5" from source so the wire gives you a more even heat.
JohnH

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Re: Question Regarding Installation of Floor Heat and Tile

Reply #2 – October 03, 2014, 08:51:53 pm

Thanks for you response, John.  I appreciate the advice.

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Reply #3 – October 04, 2014, 12:43:27 am

BRAVO! My coach has tile floor installed by one of the previous owners (I think at FOT). I love the tile...but I do wish they would've spent the negligible extra $$ and installed electric floor heat under it! I guess Texas people (owners at the time) wouldn't understand the need, hah.

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Reply #4 – October 04, 2014, 07:53:39 am

I was trying to figure how to run Air Conditioning under there!!

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Reply #5 – October 04, 2014, 08:33:37 am

If you have a slide, be thinking about total thickness installed, my slide drags slightly on the tile.  one reason am thinking of changing to cork or a thinner than ceramic floor.  Do not have the heated floor and ceramic is real cold on my feet, need rug or slippers.
otherwise love the ceramic, easy cleaning etc.  Hard on dropped glass.

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Reply #6 – October 04, 2014, 09:12:17 am

Most of my career was spent in specialty flooring. With that said I have been retired for 6 years so my knowledge is not current but from my experience I would lean toward troweling the thinset. Thinset  would be much easier to control the thickness and make the batch size commensurate with the application rate. It takes a lot more time to install in a small space and each batch underlayment has a finite time limit before it becomes unworkable.

Some issues when considering self-leveling underlayment (only read this if you are John Haygarth or of a similar nature)

The liquid loading of the batch of self-leveling is very critical. Too much liquid and the surface will become brittle and the batch will be runny making it hard to control thickness. Too little liquid and the product will not self-level and the binder will not hydrate properly making the surface weak and punky. 

Also, the temperature during installation is very important. If its too hot the product can shock out and thicken before the leveling process has completed. Try to insure that the installation temps are between 65 and 85 degrees or according to the labeled instructions

To prevent cracking in a motorhome, one needs to make sure the self-leveling product has the proper polymer modifier. The polymers can be in the form of Dry Polymer already in the powder mix or by using a liquid polymer additive such as the Laticrete 333 previously mentioned. I is important to use only a liquid polymer modifier specifically designed for the powder. The amount of water in the modifier needs to be proportionate to the cement loading in the powder otherwise the the cement will not properly hydrate. The traditional loading of water to polymer is approximately 25% polymer and 75%. When calculating the mix you need to know the solids content of the liquid modifier unless it is specifically designed for the self-leveling powder to insure you have enough water for hydration but not too much water.

I know this is all a bit tedious but it is stuff you need to know if you are considering the installation of self-leveling in a coach. Oh' and don't forget about the additional weight. 

John, I use your name with the greatest respect and your appreciation for details.

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Re: Question Regarding Installation of Floor Heat and Tile

Reply #7 – October 04, 2014, 09:34:36 am

Robert, like John H have installed many floors.

Every dime you spend its worth it. I would not get closer than 3" in any loop.

Use acrylic pre mixed grout it flexes. I would not use larger than 12" tile either, unless it is vertical.

FWIW when I install mine im going to put the thermostat in the bedroom at the foot so I can run the electric.  Once temp is set it has a probe in the tile for control. Warmtile even has a setback thermostat.

On ours with a side bath center hall my plan is for 150' wire @4" loop into the salon, bath under the table and stop at the rear door jam to the bath.

I plan to trowel the polymer added thinset because of the small space.  Be careful walking on the wire actually I would protect it w plywood and use plastic plumbing strap not the wire ties.

 

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