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Old 09-30-2006, 11:47 AM   #1
J Bone
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Installing Radiant Heating Mats on Slab

I wanted to install a electric radiant heat mats in an entryway/hallway area (high ranch) on a slab that will be tiled. This area is not flat in all areas so I was going to pour SLC to level/flatten it out, thinking the mats could be embedded in the SLC.

I read some posts and got the idea that the radiant heat won't work very efficiently without some sort of insulation under it like WEDI board. Is that true? If so, would it still be feasible to put in the heating mats by the following process:

1. Glue/Thinset Wedi to the concrete.
2. Lay down radiant heating mats
3. Pour SLC over the mats about 1/4" thick.
4. Ditra over SLC
5. Tile over the Ditra

Also, what is the advantage to using Ditra between the substrate and the tile? Would I use Ditra in any event, whether I use the radiant heating mats or not?

Thanks,

Jon
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Old 09-30-2006, 02:21 PM   #2
John Bridge
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Hi Jon,

Custom Building Products has a neat product called EasyMat that is much easier to use than Wedi. Lot's of folks can't get Wedi, anyway. The EasyMat has an R value of about 1.7 as I recall, which doesn't sound like a lot, but it makes a huge difference in the amount of heat lost to the slab.

The process would be EasyMat using thin set, heat mats with thin set over them and finally tile. You won't need the Ditra when using EasyMat.

You can check with our friends at Warmly Yours for specifications for your job. Click the link at the bottom of this page.
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Old 09-30-2006, 02:30 PM   #3
ncor
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radiant, weather electrical or hydronic heats the surrounding meida concrete can retain this heat and due to its mass hold and radiate this heat over time the best use of insulation in such an application would be under you slab to help mitagate radiante loss down ward. usually in the form of a double bubble aluminum foil vapor barrier or styreen which is much cheaper and easier to get this is placed befor a slab is laid. unfortunatly your slab already poured will radiate heat in all directions with some loss of heat to the ground. nothing wrong with slc other than its expensive thinset works just as well with due dillagance to the integrity of the mats them selves
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Old 09-30-2006, 02:44 PM   #4
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Neil, Warmly Yours recommends the insulator between the slab and heating mat.

And in this case we're not trying to heat the slab or the room; only the tiled surface.
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Old 09-30-2006, 04:22 PM   #5
J Bone
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Thanks a lot guys - one more thing John...

If I place thinset down, then Easy Mat, can I just lay down the heat mats and then pour SLC over all this, or do I have to thinset the radiant mats to Easy Mat?

If so, what surface would I prime, the EasyMat surface I assume?

I really need to make the floor flat b/c of all the undulations/bump and I have used the SLC's before and like the way they work.

Thanks
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Old 09-30-2006, 06:47 PM   #6
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Can easy mat be used with radiant heating. In talking to their customer service person a while ago it seems to me there was some restriction on using easy mat with radiant heating.

Thanks

Fred Mc.
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Old 10-01-2006, 09:56 AM   #7
J Bone
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Radiant Heat on Slab -

I guess the question boils down to this for me as far as installing the radiant heating mats on a slab:

1. Can I pour SLC over the radiant mats which are on top of some sort of insulation membrane/cork underlayment? Will the SLC bond OK to the cork/EasyMat, etc? If so, great b/c I will have that extra layer of insulation.

2. If not, can I still use the radiant heat mats right over the concrete slab, with SLC then over them? In other words, am I wasting my money or will it still heat the tile OK w/o that layer of insulation?

Thanks

Jon
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Old 10-01-2006, 10:03 AM   #8
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Hi Jon, I have done several on concrete without anything under it. The heat will rise to the tiles. Atleast it should. I haven't heard anything back from the ones I did so I would assume they work good.
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Old 10-01-2006, 10:21 AM   #9
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Jon, I've merged both of your radiant heat threads together. This way we have all the relevant background information on your project readily available. If you start a new thread with every question then something important is bound to get missed.

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Old 10-01-2006, 12:44 PM   #10
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Okay, let's start over.

There is no restriction on the use of EasyMat with radiant floor heat. We ran it by the Custom Building Products engineers not long after the product hit the street. That's how I know what the R value is.

If your floor needs to be leveled with slc I would do it before the mat is applied. Then install EasyMat with either the bonding system or with thin set mortar. Then install the heating mat with thin set and finally the tile with thin set.

As Musky Mike indicated, the installation will work without the insulator above the slab. It won't work as well, though.
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Old 10-01-2006, 01:10 PM   #11
J Bone
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Thanks, that clarifies everything for me, the only thing I am concered about is it easy to get a nice flat surface by thinsetting the mats down for a guy who's not an experienced tiler or mud man? I guess you just use the side of the trowel that is unnotched and just screed the thinset over the mats?

I definitely would do the two-step process - mat, thinset and let dry and then layout the tile and thinset it down, I am just a bit worried that I won't be able to get the surface nice and flat like I would with the SLC..

I think I will go this route though b/c it sounds like the radiant heat will be much more efficient...I'll just take my time I guess
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Old 10-02-2006, 12:01 PM   #12
ncor
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thanks john just stuck on hydronics insulation a must here also
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Old 11-29-2013, 09:40 AM   #13
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Still recommend "Easy Mat"?

As I am reading this thread, I wonder if you still recommend this product as opposed to other newer products for insulating my heating mats from the cold slab. Thanks.
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Old 11-29-2013, 12:05 PM   #14
jadnashua
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EasyMat comes in several forms, I've never used it, so this is only hearsay, some have had issues with the self-stick stuff. I think that only comes in the thinnest version, which you probably wouldn't want. I've never used Wedi, either, but it is foam sheets - comes in various thicknesses, and is the only foam sheeting material I know of that can be thinsetted to a slab.
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Old 11-29-2013, 06:01 PM   #15
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I'm a Cerazorb guy. Yes, it will work as a thermal break,yes you can pour SLU over it so you will get a flat tile surface. Level is desired, but FLAT is required for setting tile. Two floor heat companies that I know of that also sell Cerazorb is WarmlyYours and Thermosoft
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