radiant subfloor

Paul Fredricks_3

We have an area in our office where we are considering radiant heat. Due to the way that area and the next join up, and the way it's built,  we can't put anything on the current floor and we can't get under it for staple up.



What we have to do is pour a sub slab to bring the concrete level up, then put down mesh with the radiant ty wrapped to it, then pour over that.



I guess



My question is: How much room do I need to put down the wore mesh and the tubing. I was thinking about 7", but is that enough? I figured that would leave enough room for 2" foam board, the mesh and the tubing, leaving the tubing 2 -3" below grade. Does that sound right? I don't have a lot of experience with radiant installation.

Bob Bona_4

Hi Paul

You want the tube at least 3/4" below the top of the pour. I'm not understanding the layers you are describing though. The sub slab is an overpour to the existing slab?

Paul Fredricks_3

Yes

And now I'm not sure it's going to happen, but things change. The existing sub floor was part of a garage years ago, so one side of it is 7" below the floor next to it. The other side is about 14" down, so there was a bit of a slope. The idea would be top pour the whole thing level, then (I'm assuming this is the way to do things) put down foam insulation, then that rebar mesh, then ty-wrap the tubing to that, then pour over everything to level.

Bob Bona_4

have the

height you want in the room once the two slab elevations are level and you add the board and another 2 1/2- 3+ inches for pour on top of all of it?



Not that I'm a big fan of bubble foil, but I have done a lot of garage makeovers with it on the original slab, used Uponor's plastic brackets. .22 shot with fender washer nails Hilti'd into the slab. I spread them 2 feet apart. Tubing snaps into the brackets. 2" overpour follows. Then finish floor. The BF was to save headroom, and for threshold alignment. Better than nothing. You could also Hilti shot down the tube and skip the brackets, but the brackets hold the tube up just a little, maybe better for slab/tubing integrity?

Don't forget to embed a 3/8 copper line for a sleeve (use oil line, flatten embedded end) for your slab sensor. Hilti it to the old slab with electrical conduit clamps and watch the bends, as in make very gradual ones-make sure the sensor bulb can get around the corners..test fit ahead of time to be sure, and note the insertion depth for snaking reference. Have it come out someplace you can get to to snake the sensor in. I use Uponor's 511s stats.

NRT_Rob

hmm

if you have 7" to play with, you could do 2-3" of rigid foam, then pour over that. Tubing could be anywhere in the pour.



or you can do a level coat, insulate, and pour over that if the base slab is not flat enough for you. You can do tubing in an overpour of 1.5" thickness or greater, and if you go over 4" in thickness I'd start looking for a way to lift the pipes off the bottom of the slab.

Paul Fredricks_3

Plan Change

OK, looks like the plan has changed. I think we are going with Quick Track. Does anyone have a problem with carpeting placed directly over the Quick Track?

NRT_Rob

I do

some disagree, but I never want to see a plastic pipe installed without something hard between it and the finish floor surface.

Paul Fredricks_3

.

That was my thought too. Unfortunately we don't have the room to put anything on top. I guess if it is just carpeting and pad on top it wouldn't be too hard to get to a leak. This is in an office space with cubicles. we may just need to be careful on where and how furniture is placed.

Bob Bona_4

can you

afford a 1/4" of Hardibacker board over the QT, Paul?

Maybe cut out the pad or go with the thinnest possible, just to protect the tube.

Scenario: Somebody drops a thumbtack. Somebody steps on said thumbtack. Tube happens to be directly under it.

Paul Fredricks_3

...

In reality, no. We'll be dead even with the concrete floor next to it. I hear what you are saying though. Maybe we'll look at it again after the Quick Track is down.

Paul Fredricks_3

ok

Yeah, OK, the backer board will work. Forget what I said. The floor is so uneven that a little elevation change is not going to effect anything. The suggestion by the rep was to put the backer board down with a little thinset. Thanks guys.

Bob Bona_4

it's going

to work awesome with the cementboard.

Router a 3/8" channel in between two tracks, in an "average temp/middle of a loop area" to embed the copper sleeve for the slab sensor, before the Hardi. Be sure the sensing bulb can make it around bends.

I use piano wire taped to the sensor bulb lead every foot or so for fishing, and wrap a colored piece of tape at the full insertion length of the wire so you know you've bottomed out, or have more to go. I do this at the test fit of the bulb, in the beginning of the project. tekmar bulb leads are 10' approx.