Levelling Thinset over WarmlyYours Heating Pad

[Chris D]

I just got our warmlyYours infloor heating pad for laying under tile. The pad only goes under the main area of the bathroom floor, but at 1/8" it will create a ledge along the edge.

Is there a trick to using the thinset to accomodate this difference in height?

Should I "skimcoat" an 1/8" layer of thinset over the unheated areas to make them level with the heating pad, and once that thinset has dried, then put down the required 3/8" layer of thinset for setting the tile over the heating pad?

Chris

[David Taylor]

That's the ticket.

Use a grout float over the wires to cover them up with thinset. Let that harden a few hours and then do your skimcoat out a couple of feet to the unheated area. The difference will be very subtle.

[Davy]

Hi Chris, I use thinset for a skim coat over the wires to hold them in place but it's not very easy to work with, some guys use SLC. If you use thinset you might have to rub down the floor lightly with a rubstone the next day to knock down anyl ridges left but careful not to rub the wires. I use a flat trowel for the skim coat. The 3/8 thinset would be from the notched trowel while installing the tile. I agree with David, go ahead and skim coat outside the wires too. If it's a big area you can taper the thinset down to it.

[doitright]

Hi Chris

What are you attaching the Warmly Yours matts to?

[Chris D]

I am attaching the heating pad to 1/2 inch Hardibacker 500 that has some thin-set already on it over the joints etc...

Warmly yours said we should use a latex or acrylic-based or admixture with the Thinset, but at the class we went to the instructor told us that we should use only water-mixed thinset.

Which is the greater risk for floor tile application: latex/acrylic admixture thinset making the tile less stable or water-based thinset application doing some unknown harm to the warmly yours heating pad?

Chris

[doitright]

Hi Chris

Have you bonded the mat at all to the Hardieboard? If not, securing it with some double sided tape, and using a hot melt glue gun will assist in stabilizing it. Trying to drag thinset over it, without you using three hands, will be difficult.

Where are you located, and where were the classes being held?

I haven't heard of any acrylic latex or modified thinset harming the mesh or coated wires, or being unstable.

Make sure you keep that alarm hooked up and turned on for the entire install. Also make sure you dampen the Hardiboard before applying the thinset.

[Chris D]

I am just using a glue gun to bond the mats to the hardibacker. I did not see any mention of double-sided tape in the installation handbook. I think the glue gun adhesive will hold the webbing well enough.

[doitright]

The glue gun will do just fine. There is a competitive product that includes the double sided tape in their installation kit. Make sure you keep the gun tip away from the cables. If you get some glue globs to high, and they're not near the elements, you can rub the hot gun tip against them to lower them (if needed).

Chris, Keep up the good work!

[Chris D]

One last question (before I have any more questions, of course):

I got some self-levelling cement underlayment but have not used it yet. While at Home Depot I noticed the stuff and it seemed too appealing to pass up. It seems like an ideal way to smooth out the skimcoat over the wires before laying the final thinset & tiles.

I have a float to use to spread the stuff out as needed.

What consistency should I make the stuff. The description on the bag is not very clear.

Pancake Batter? Cookie Dough?

Chris

[doitright]

Hi Chris

A couple of important suggestions.

If you use the SLC, you should prime the Hardieboard with their primer. It's ok to prime over the wires.

Next the bags are usually quite clear on the amount of water to mix the entire bag. I believe it's 6.5 quarts. The water should go into a 5 gal. bucket first, and start adding powder. I add about 1/2 the bag, mix it in, and add the remainder of the bag. You're supposed to mix for about two minutes (obiviously a drill and paddle is needed for this procedure).

The consistency is quite watery. Don't let it fool you, it will start to set up quite quickly, and you have to hustle for the next batch.

I recommend you use the search feature on SLC to become a little more familiar.

[WadeJ]

I didn't notice this post before, but for future knowledge you MUST use a latex modified thinset with ANY and ALL electric floor heating jobs. I have no idea who was teaching that class, but whoever it was, they were wrong. Call any thinset manufacturer and they won't warrant basic thinset when electric heat is installed. We've recommended latex modified thinsets for 10 years and have never had a problem with them.

The water based thinset won't hurt the heating cables at all, but the heat may cause the water based thinset to crack/crumble over time.

Wade J

[David Taylor]

That's pure nonsense, Wade.

If that were the case, all the jobs over concrete would be failing left and right. The sun, direct or not, can make a floor much hotter than the electric cables can.

The problem is that people are curious to see if the floor works and activate the mats before the thinset has had a chance to hydrate or dry out. It's the reason why the mat manufacturers say to leave the installation for 30 days and then activate the floor slowly, gradually increasing the temperature.

The thinset manufacturers have an agenda of their own...please don't perpetuate it.

[WadeJ]

David

Goodness knows it's not the first time I've been non-sensical.

If I'm perpetuating a myth of the thinset manufacturers, then I'm guilty, but it's not my job get in an argument between my customers and the thinset manufacturers, and if the thinset manufacturers will look for an excuse to say the floor failed, and that excuse is regular thinset with an electric floor and we didn't recommend latex modified, then the customer would blame us for not telling him.

We'll still recommend the latex modified thinsets, but it's good to know that if someone does use regular thinset by mistake it won't ruin the floor.

Can I ask a question though, is it correct to assume that latex-modified thinsets have a better bonding strength then water based thinset? If so, wouldn't it make sense to use the latex-modified versions since there will always be some interferance with the thinset bonding to the floor, even if it is a small wire?

Wade

[Mike2]

Hi guys.

I don't want to get into the middle of this - just offering a suggestion. Let's move the debate over to the Pro Corner. How about it? First one over there starts the Thread, OK?

[David Taylor]

See you there