Radiant Heat underneath tile [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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03-10-2006, 08:37 AM
I'm just beginning to tile our new master bathroom, and have installed the Warm Tiles radiant heat system on the floor. The floor is 3/4" T+G Plywood. I am going to cover the radiant heat cables with a layer of self levelling concrete (Easy Flow) and it requires a primer be applied to the subfloor. My question is, the cable is already strapped to the floor, is it alright to apply this primer with the cables there? I didn't realize a primer was required or I would have done that first, but now, it would be a lot of work to rip up the radiant heat cable, primer and then reinstall cable. My concern is that the primer might damage the heating cables somehow.

Any advice greatly appreciated,


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03-15-2006, 01:33 PM
Allright, since nobody's got any thoughts on the primer damaging the cable for the radiant heat, how about this. Would it be allright to apply the SLC (E-Z Flow) over the subfloor/radiant heat without applying any primer at all? What is the primer really needed for, and is it absolutely necessary. I plan on putting schluter overtop of the whole thing anyway.


03-15-2006, 01:42 PM
Call or E-Mail the cable mfg. for there guidence.Let them know what the primer is..My guess is that it would be fine since its most likely Latex and that shouldnt hurt PVC or CPE wire jackets.But what do I know???They may say "what are ya goofy"?

03-15-2006, 01:44 PM

I don't know much about plywood, and nothing about SLC primer. I know something about heat. I may be the only one reading your thread.

1. Your thread is labelled "Radiant Heat underneath tile" but it should be labeled "Primer - needed for SLC?" in order to attract the right guys. A moderator can change the thread title for you, if you send a Private message asking for it to be done.

2. Call an SLC manufacturer to see what they say, too. Always good to share what they say too.

Hope this helps you get farther ahead.

03-15-2006, 03:52 PM
This is the manufacturers description of the product:

Product Description
E-Z FLOW PRIMER 100 is a premium waterbased primer and bonding adhesive specifically formulated for priming and bonding new cement, stucco and plaster to old concrete, wood, tiles, slate, terazzo, brick & mortar surfaces. It can be used interior and exterior, on walls, floors, concrete sidewalks, driveways, patios, steps & curbs. E-Z FLOW PRIMER 100 prevents pinholes from forming in the new topping.

The MSDS lists it as a Vinyl Acetate Polymer.

As for talking to a manufacturer rep, they were pretty much useless.


03-15-2006, 07:19 PM
You'll be sorry if you don't use the slc's designated primer. You might want to call the heatmat's manufacturer, but my guess is that the primer won't hurt it any. Carefully adhere to any time restrictions between application of the primer and the slc if there. Different brands have different timing. The one I used said slc within 4 hours of drying or recoat. The timing varies by manufacturer and configuration. It would have been better if you had done the primer then the heatmat then the slc, in my limited experience with the stuff. You'd have to work quick, though. One of the pros with more expeience with the stuff will show up eventually.

03-21-2006, 10:17 AM
Search for posts by, or send a PM to, MarcusEngley or Flatflor. I'm pretty sure both of them have primed directly over WarmlyYours (or Suntouch) before and then laid the self-level.

I don't think it will be a problem to prime over the heating system.


03-21-2006, 12:46 PM
Hi Rob,

I'm not in the same league as FlatFloor, but I DIYed my SLC over Wade's Warmly Yours mat (hi Wade! -- floor's working great!) -- no problems with the primer. It's just a soupy latex that helps with adhesion between the plywood and the SLC. Keep posting the questions on this thread, we'll keep you on the right track.