# Heated floor over slab



## HandyHails (Feb 28, 2009)

Simple question.

I've done dozens of heated floor installs at this point. Never over a concrete slab though. 

Any special tricks or recommendations anyone found to make sure these adhere to the slab. Really the only problem I've ever had w/ these electric blanket type systems is that they like to float to the top of the self leveling compound.

I've solved that issue completely by using wire lath over the heating element and stapling to the subfloor. Obviously this is not an option here. 

Any of the mesh mount systems more "sticky" than others? Would it me an option to strengthen the adhesive on these w/ a secondary product? 3M spray adhesive comes to mind.

Thanks,


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## EthanB (Sep 28, 2011)

I can't say from personal experience but I've seen guys laying them in with hot glue.


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## heathwwilson (Jan 31, 2012)

I just finished one spray adhesive does work but normally I can just use the double sided tape that's on the may then use the roll that comes with it to tape down edges and corners you can also use duct tape but only on the may part try not to cross it over the wires


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## Tech Dawg (Dec 13, 2010)

Noble EXT may be a good option? but I'm not sure if that can be used with heat. That stuff is pretty sticky... or maybe use rapid thinset and embed it with a stick of PVC.


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## angus242 (Oct 20, 2007)

Laticrete mats have self-adhesive backing.


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## GO Remodeling (Apr 5, 2005)

Warmly Yours (heat matt) suggests you use cork under the matt-on-slab installation. It's suppose to put the heat more into the tile than the slab. I've done two installs like that. I thinset the cork down with modified and go over it with a roller. Let dry overnight. Next day, hot melt the matt down and prime it real good. Let primer dry to directions and pour the leveler. Take all the regular precautions with leveler. No worries.:thumbsup:


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## Tech Dawg (Dec 13, 2010)

I just saw in the Laticrete spec's that you can use the 170 sound and crack isolation mat to keep from losing heat. I'm sure their heat mat would stick right to it :clap:


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## angus242 (Oct 20, 2007)

_Does LATICRETE 170 Sound & Crack Isolation Mat provide any insulation value for LATICRETE Floor Heat?_
No. LATICRETE 170 Sound & Crack Isolation Mat has an R value of only 0.1 so it will not be effective as an insulator for radiant heat systems.


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## Tech Dawg (Dec 13, 2010)

angus242 said:


> Does LATICRETE 170 Sound & Crack Isolation Mat provide any insulation value for LATICRETE Floor Heat?
> No. LATICRETE 170 Sound & Crack Isolation Mat has an R value of only 0.1 so it will not be effective as an insulator for radiant heat systems.


Let me reread this... Ill be back :laughing:


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## EthanB (Sep 28, 2011)

I think Angus is dead-on in this(what's new?). I just tried to spec an electric radiant mat for a slab application and there's just no thin way to prevent the majority of the heat from heading down. It's really a tile warmer so the total energy loss shouldn't be breaking anyone's budget that can afford the product in the first place.

What I DID find as an alternative for larger spaces is a new product from Uponor that is for hydronic systems. It's an adhesive mat with a thermal break that the pex snaps into. It comes in two thicknesses. As long as you can raise the floor by 1/2" it looked like the way to go for an actual heat source.


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## angus242 (Oct 20, 2007)

I think the only way possible (without alternative like Ethan posted) is a cork underlayment. I've never used one so I have no idea of their cost.


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## Tech Dawg (Dec 13, 2010)

I've never used the 170 but I was reading off the mobile app where it says that it can be used as a thermal barrier to prevent heat loss with the floor heat. I didn't look at any spec's though :wallbash:


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## EthanB (Sep 28, 2011)

Cork's R-value is apparently around 3 per inch so that doesn't sound like it'd do much. You'd be better off with a foil faced thermal break but I don't know if such a thing exists that you can use under radiant mat and slc.

Edit: Disregard most of the above. I shouldn't post while watching TV. The cork would work as a thermal break because inside the slab we're talking about conductivity so even a thin layer would be a big help(imagine standing barefoot on 60 degree concrete, now put 1/8" of cork under your feet). That said, I still don't love the idea of putting cork on top of a slab that might wick water so maybe something like the Wedi Board would be safer.


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## HandyHails (Feb 28, 2009)

olzo55 said:


> Warmly Yours (heat matt) suggests you use cork under the matt-on-slab installation. It's suppose to put the heat more into the tile than the slab. I've done two installs like that. I thinset the cork down with modified and go over it with a roller. Let dry overnight. Next day, hot melt the matt down and prime it real good. Let primer dry to directions and pour the leveler. Take all the regular precautions with leveler. No worries.:thumbsup:


Just 12x12 squares? Have you ever done it over a slab without cork? If so, was there a significant difference in performance?


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## HandyHails (Feb 28, 2009)

I will check w/ my supplier this morning, but I've found this in the mean time.


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## JohnFRWhipple (Oct 20, 2009)

I would be careful with the spray adhesive. This could create a bond breaker.

Hot glue gun is a little risky as well but I'm guilty of that install method on occasion.

As a rule the blanket type systems simply - "How can I say it nicely?" SUCK.

Use a cable system.

We just had a job go South that was NuHeat heating pads over concrete slab (Condo) - The concrete finish floor cracked all over the place.

The concrete guy blamed me. NuHeat stood Neutral. I blamed the concrete guy (over watered product) and also pointed fingers at the mats.

I suggested the client get the samples "Tested" - which he did and in the end Nu Heat bucked up for all new cable (NOT MATS!!!!) and the client went with a better cement company. It took them two days to grind the 253 and fleece mesh off the slab. :whistling I wonder how well we did installing the mats... :laughing:

The new crew used Ardex's product line and installed a 6 step finish.

After seeing the separation first hand of the mats where they seam together we will never install a heating mat again.

I prefer the control I get with the wire system anyway and the last few jobs we have used the Cosco heating kits which are very similar to the Laticrerte line. This Laticrete heat wire / mesh is a very cleaver design and very easy to install.

JW


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## HandyHails (Feb 28, 2009)

Generally speaking, I almost always use cable type WarmTile. I just don't see any real efficient way of securing that to a slab, or even the cork without a ton of hot glue or other types of solutions like that. I don't mind using hot glue, but I try to keep it to a minimum. When working over wooden subfloors, I don't use it all.

BTW this install is going to be a total of 55 square feet of heat.


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## angus242 (Oct 20, 2007)

Josh, everything I have read states that and a 1/4", most materials are worthless for containing thermal loss. Even cork has an R-value of < 1 at 1/4". I'm not sure you're getting any value for the cost of it. Besides, I think that QEP stuff recommends installation with mastic :blink:


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## JohnFRWhipple (Oct 20, 2009)

HandyHails said:


> I will check w/ my supplier this morning, but I've found this in the mean time.



I installed cork in my basement mud room 1/4" standard type used for wood floor installs as a sound proofing product. I used laticrete 254 and rolled it with my medium roller. The mud room is so much warmer with just the cork we have decided to skip the floor heat!

It is amazing the thermal break a 1/4" cork does.

The problem with this method is finding a setting material to go over top. Mapei has not recommendations and Laticrete does not suggest any products to work with cork.

I have not finished this mud room but plan on setting a 3/4" - 1 1/4" mortar bed over top and will most likely buck up for some Screed Mortar from Mapei. I figure if I can smash the Mapecem with a hammer at 1/4" thickness a full 3/4" will be tank like.

I understand the issue from the suppliers to be the compression of the cork. Like the same issue with tile over Vynal flooring.

JW


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## JohnFRWhipple (Oct 20, 2009)

angus242 said:


> Josh, everything I have read states that and a 1/4", most materials are worthless for containing thermal loss. Even cork has an R-value of < 1 at 1/4". I'm not sure you're getting any value for the cost of it. Besides, I think that QEP stuff recommends installation with mastic :blink:


Angus when you make it to Vancouver you can stand on the cork with one bare foot and the slab with none. This room has warmed up to the point of not needing heat.

The only change to the room was installing the cork!

How thick is your coffee cup? It keeps your hand from getting to hot. And keeps your coffee warm???


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