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09-09-2001, 06:11 PM
We are building a new house and wish to use infloor heating. In the basement this is not a problem. The problem is over the wood floors. We were considering using Gypcrete or gypsum concrete to cover the heating pipes, but some message boards seem to be against this procedure. The other factor is the approximately $3 per square foot cost. Is there another product that we could use to avoid the problems that have been linked to Gypcrete? Is there a self levelling Portland cement or other product? Under what trade name would it be available? I live in Ontario Canada.
We were going to use radiant water heating probably with the 1/2" Wirsbo pipe. The kitchen, bathrooms and dining room will be either laminate, vinyl or tile. The bedrooms on the other hand will be carpeted. We have been informed that we will have to insulate under the floor to overcome the R value of the carpet and underpad, and direct the heat upward rather than downward to the lower level. We do not wish to have a dual system, of forced air and in floor, and are trying to work out these details before we start. We will be starting in about 2-3 weeks. Any help would be appreciated.

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Rob Z
09-09-2001, 07:03 PM
Hi Gary

Thanks for visiting the forum. I don't have any experience with radiant heating. It's not very common here in Virginia.

I have always used portland cement based self leveling products, and have avoided the gypsum based ones because of the same negatives you have heard about.

As for cost of a large scale SLC pour, I'll ask Jim Buckley to stop by.

Visit to see if they make a mat that contains the pipes and also serves as a base for SLC or thick bed mortar.


09-09-2001, 07:26 PM
I'm not 100% sure, but I think that company offers a wood substrate with grooves set into the wood, where the tubing would be placed. It has a foil surface that directs the heat up. Any additional flooring can be layed directly on top, since the tubing is not exposed, and is flush with the rest of the floor. This would solve the gypcrete problem, though I'm not sure if it would be cheaper.


Rob Z
09-09-2001, 07:31 PM
Hi Bri

Is that stuff called ADVANTECK? Dave Ashton did a job with it, I think.


09-09-2001, 07:36 PM
I'm not sure what its called,but I just came back from the Wirsbo site, and they do have a "decking" that is similar to what I decribed.


09-09-2001, 07:47 PM
Didn't we do this one before? The depth and the gypcrete seem familiar. How many square feet are we talking about? Befrore we go any further with a slc (self leveling cement), be advised it's not going to be cheaper, just better.

09-09-2001, 07:58 PM
Gee that is a fast response!
The house is a side split, with one level, the kitchen/dining and living area about 880 square feet, and the bedroom level about 780 square feet.
Jim, you had mentioned to me before that you do not market your product in Canada. Is there a similar product available from the cement companies? LaFarge, Blue Circle?
I looked at the schluter site, and they do have a plastic mat to lay down, fasten the heating pipes to, pour some type of thin cement or gypcrete over, and then apply floor goods.
I am still confused by all of this, but I really would like to find a viable solution to enable us to have the infloor heating system.
Thanks for all your responses so far!

09-09-2001, 08:16 PM
Hello again, I thought this was familiar. We have several Canadians on this board, one of whom yells at me for misspelling Canadiens. Let's see what they suggest product wise. This board may close down for a few days so use my website to email me. In the meantime I will email procedure for WOOD installation. Better yet I'll post it here now.

Equipment Needed:
Soft Push Broom--to apply primer
Caulking gun-seal seams of plywood subfloor and any other openings!!!!!!!!!!!!!!!!!!
Sheetrock knife/or other sharp instrument--open bags
2-New Sturdy garbage pails--one for mixing--one as a water reservoir
Garden Hose--keep attached to replenish water reservoir
Plastic water bucket--premark with indelible marker to 6-qt. level use a light color pail

Jiffy mixing paddle or E (# 12-851-B7) from Bon Tool
Epoxy finisher F (# 14-915-B8) Bon Tool
Epoxy spreader G (# 12-689-B7)--you may be able to get away without this and just use the finisher but it does take a certain amount of experience, but considering the first lift is over the tubing, quality is not critical at this point. By the time you are ready to apply the finish layer you will have a good feel for the material.

2 HD 1/2" drills--1 for backup
Extension cord
Plastic drop cloth -- to protect mix area surface and if you want to be really cautious, one on the floor below you in case of leaks

2 Men mix and pour
1 man spread and finish material

1) Caulk and plug openings (This material WILL seek it's own level)
2) Prime wood, first coat dilute 2:1 with water plywood should suck this up and dry quickly, then apply second coat diluted 1:1 primer. Get rid of any puddles. Clean the broom with water.
3) Install wire mesh, stay off the primed surface! Be sure to fasten mesh to floor every 6", especially along the edges, otherwise mesh will float when pouring cement.
4) Install tubing

Fill up garbage pail reservoir
Line up and open enough bags to do this phase approx. 1" deep.
Pour 12 qts. water into mixing pail slowly add two bags SLC, mix and carry ( 2 men ) and pour onto surface, while this is being spread mix next batch. Repeat until all tubing is barely covered. Mix and pour continuously, always pouring onto a wet edge. The mixing and pouring should take at most two hours. Block entrance to room, you wouldn't believe the stories I can tell you about people walking in this stuff, including the guy who climbed over a wet floor sign and then told me I should have put up a sign, or the school teacher who got through a door that had been wired shut in order to take a shortcut across the gym.

Prime the floor again, use the fan to accelerate drying or leave and do something else then come back, watching primer dry is boring, and pour the final 1/4" or 1/2". That's it!

Fan will accelerate dry time for primer, ok to pour when it's tacky. You actually have more than a 24-hour window to pour within. We limit it to 24 hours because invariably people will walk on it the longer it is exposed. Feel safe up to 48 hours.

When wet, material may appear to have high or low spots especially if there are a lot of windows, light causes reflections and optical illusions when material is wet. Try not to work the material too much, just enough to distribute it evenly. The worst thing you can do is try to work the material after it starts to set, DON'T.

If while your pouring you see material going down an opening you missed simply put a handful of dry material in the opening, this will plug it up instantly. Just drop it in the opening.

This particular installation is a great way to get used to the material since the first pour is a "practice" no need to be overly concerned about it, since the second coat will hide any irregularities. Once you finish the first coat you will have a good feel for the material and the second will be a piece of cake.

All of this may not apply depending on how deep you plan to go. You may be able to do it in one pour.

[Edited by flatfloor on 09-09-2001 at 10:26 PM]

Rob Z
09-09-2001, 08:27 PM
Jim,thanks for the info.

09-09-2001, 08:32 PM
Hi Gary

Have you considered using the the infloor heating system that is installed under the floor, between the floor joists? I'm not sure what it's brand name is, but it's great for a new home installation, since the floor is still accessable from the basement.


09-09-2001, 08:39 PM
Again I went to the Wirsbo site, and it can be installed between the joists, so if you do it that way, you won't need to fool around with gypcrete or whatever..

check it out


09-10-2001, 02:10 PM
Gary, looks like Brian may have something if you can work with it. Just to give you a better idea of slc cost at a depth of 3/4" over 1660 SF you would need;

260 bags x $25/bag= $6500(US) or 10,156 CAD= $6.12/SF and that does not include mesh, primer, or labor. You might be able to get the bags cheaper, say $20 US=$5200=$8122CAD=$4.89/SF

Try to engineer Bri's suggestion.

09-10-2001, 05:11 PM
Thanks for the replies.
We looked at putting the pipes under the subfloor but then you have to overcome the insulative properties of the plywood. Secondly, I have heard that this method, and using the heat transfer plates can be noisy due to expansion and contraction of the pipes and plates.
Thus we wanted to keep the pipe on top of the subfloor, and embed it in some kind of concrete material. Unfortunately, it appears that Gypcrete, Therma Floor or other brand names for gypsum based concrete, are the only choice. It is self levelling but it appears that it has alot of problems.
We tried using sand mix on one job, but the surface ended up quite rough, and uneven. Then there was the problem of the cracking as it dried. This will be its first winter, so we are not sure how it will work out. I figured there had to be a better way. Hence my post here.
We can get the gypcrete poured for about $3 Cdn per square foot. It does not seem to be available by the bag.
I really appreciate all your input.

09-10-2001, 06:11 PM
What about electric radiant?

Are you the builder?

09-10-2001, 07:49 PM
I'm not sure why your sand mix job was rough and uneven..but Gypcrete takes forever to cure before you can put flooring over it...and it cracks also. What part of Ontario are you in?..I might know a guy..who know's a guy..


09-11-2001, 04:21 PM
We thought about electric radiant, but we started seeing BIG $$$ signs for our monthly electric bill.
Yes, I am the builder.
The sand mix job was not trowelled, and was just screeded off the top of the Wirsbo pipe and mesh, and floated. My job was mixing the sand mix.
I am west of Toronto and east of Kitchener near Guelph.
Thanks again for all your input!