Pex tubing installation

[Jagman]

I am planing to build a new 23 x 32 garage this spring with radiant floor heat. My contractor has suggested that in preparing the slab, the Pex tubing first be attached to the 2" floor insulation before placing the wire mesh w/chairs over it. This in part because I will be installing a four post lift and he is concerned that in making cuts to the floor (4" slab) he might puncture the Pex tubing. He has also suggested placing sleeves over the Pex in the areas where the cuts will be so expansion and contraction of the floor will not affect the Pex tubing.

Does this sounds like a good plan?

John D.

 

[stingry]

I am planing to build a new 23 x 32 garage this spring with radiant floor heat. My contractor has suggested that in preparing the slab, the Pex tubing first be attached to the 2" floor insulation before placing the wire mesh w/chairs over it. This in part because I will be installing a four post lift and he is concerned that in making cuts to the floor (4" slab) he might puncture the Pex tubing. He has also suggested placing sleeves over the Pex in the areas where the cuts will be so expansion and contraction of the floor will not affect the Pex tubing.

Does this sounds like a good plan?

John D.

When I did mine, I attached the pex directly to the 2" EPS and layed the 6x6 mesh directly on the pex. No need for the chairs, this method puts the mesh towards the bottom of the slab where the tensile strength of the mesh is needed. When done this way, you know exactly where the pex is and can saw cut accordingly. As for the sleeves, pex is very tough and resilient and should not need the sleeves but certainly won't hurt if you want the additional security of having them. I own two self-serve carwashes with pex in the slabs. Both have sawcuts and cracks and have not given me any problems in the 10+ years they have been in operation.

Cheers
Steve

 

[arb905]

Can I get some clarification? I have a 45x36 slab I am prepping to pour. I have an old boiler I thought about using for floor heat in there. I know there is a need to insulate, so insulation, over the rock base, pex laid out as designed on the insulation then 6x6 metal mesh panels on the pex? No rebar? I woudl assume if the mesh is over the pex then the concrete will settle under the mesh and any drilling should be limited to 3" deep on a 4" slab?

 

[Jess]

In my recent 32'x40' shop build, we used 2" XPS (blue stuff) under the slab over gravel and 6mil poly vapour barrier, 2" XPS around the floor perimeter, 5/8 rebar on 16" centres and 10 ga 6x6 mesh on top of the rebar. Once the 1600' of 1/2 pex was tied to the mesh, we lifted the rebar onto 1 1/2 chairs. Concrete was placed with a line pump and power trowelled to a smooth finish. We did go thicker at the door to support heavy loads as they cross the footing but it might not be necessary if you don't have crawlers and other heavy iron. There won't be any issue with stapling the pex to the foam but it takes longer to heat up if its in the bottom. The design should address that for you. The suggestion to sleeve the pex at sawcuts and where it exits the slab is a good one to reduce the risk of potential damage. The slab was kept wet for 2 weeks after the pour and 3 years later, no cracks.

Jess

 

[arb905]

I did find a website that sells clips that screw into the foam and they suggest putting the mesh on top of the pex. I don't mean to hijack this thread. I have concerns and they haven't been addressed in my thread. My concern with the pex is the fact that I am splitting a large building in half. I intend to put up a wall and not sure where I want to or will put a lift. I assumed if the pex was at the bottom of the slab and limited any holes to the top of the mesh then I wouldn't hit a line and I can securely anchor the lift. I may just forgoe the radiant heat and put in a central system. I am more concerened about heating in the winter than cooling in the summer.

 

[stingry]

I did find a website that sells clips that screw into the foam and they suggest putting the mesh on top of the pex. I don't mean to hijack this thread. I have concerns and they haven't been addressed in my thread. My concern with the pex is the fact that I am splitting a large building in half. I intend to put up a wall and not sure where I want to or will put a lift. I assumed if the pex was at the bottom of the slab and limited any holes to the top of the mesh then I wouldn't hit a line and I can securely anchor the lift. I may just forgoe the radiant heat and put in a central system. I am more concerened about heating in the winter than cooling in the summer.

As stated in my above post, I stapled the PEX to the 2" EPS, then layed the 6x6 mesh on top of the PEX. No rebar since the floor will only see light loads, cars etc. I would recommend using the staples over the screw-in types just because of the ease of installation. Check out this site http://www.houseneeds.com/, they have the staples and will rent the installation tool. By using this installation method, you know exactly where the PEX is located and how deep you may penetrate the concrete. I used tapcon screws to anchor my interior walls. You only drill 1 1/2" max with the tapcons. If you are considering a four post lift, you do not need to anchor to the concrete, two post lift yes. If planning on a two post lift, I would decide where you may want it and then leave the radiant tubes out of this area.

Steve

 

[CARS]

How deep are the relief cuts in the slab?? Shouldn't need to be deeper than an inch would it?? Farly small slab too. 1 cut down the middle or are they quartering the slab??

I posted a link on the 3rd page of "in-floor heat disappointments" that I found this morning. It talks about getting the pex up as high as it can in the slab for proper heat transfer (help it come up more than trying to go down).

 

[Jagman]

I'm not sure yet as to how many cuts are contemplated. I believe they are supposed to be about 12' apart. My slab will be 23x32. With a 4" slab, the cuts only need to be 1".

I was also thinking of putting a layer of wire mesh on top the EPS and using it to tie the pex in place as an alternative to tying the pex to the EPS. I would then add a second layer of mesh on top of the pex. I have heard that if the mesh is at the bottom, it offers little in the way of strength to the slab. Alternatively, I could tie the pex to the mesh and then raise the mesh up an inch or so with chairs. However, if chairs are installed, it would seem that you can't step on the mesh when pouring the concrete. Having never done anything like this before, any suggestions are welcomed.

John D.

 

[stingry]

I'm not sure yet as to how many cuts are contemplated. I believe they are supposed to be about 12' apart. My slab will be 23x32. With a 4" slab, the cuts only need to be 1".

I was also thinking of putting a layer of wire mesh on top the EPS and using it to tie the pex in place as an alternative to tying the pex to the EPS. I would then add a second layer of mesh on top of the pex. I have heard that if the mesh is at the bottom, it offers little in the way of strength to the slab. Alternatively, I could tie the pex to the mesh and then raise the mesh up an inch or so with chairs. However, if chairs are installed, it would seem that you can't step on the mesh when pouring the concrete. Having never done anything like this before, any suggestions are welcomed.

John D.

Seems like a waste of mesh to me. The PEX staplers work really good. You just place the PEX on the EPS, place the tool over the PEX, push down and the PEX is stapled to the EPS. Yes, if the mesh were layed on the EPS, it would offer nothing structurally. By laying it on the PEX, it becomes embedded in the concrete towards the bottom of the slab, providing tensile strength to the slab where none is provided by the concrete. Concrete is very strong in compression but extremely weak in tension.

 

[Jagman]

Stingry,
If I opted to just staple the pex to the EPS insulation, how easily can the staples be removed if I needed to adjust the position of the pex?

Thanks for your input.
John D.

 

[stingry]

No problem to pull out, they are just plastic with a couple of barbs on each end. Go to the website that I recommended in the earlier post, there will be a picture in there of the staples and the installation tool. Also Menards stocks the tool and staples if you have one near you.

 

[Novicaine]

For control joints, I've read that you can put those drywall thin steel corner pieces on top of the pex where you want a joint (so one edge is horizontal, one is vertical), pour the concrete, and the concrete will naturally crack there if it is going to crack, then you don't need to cut control joints yet you'll have straight cracks. Also, you can then sleeve the pex under the control joints if you want.

EDIT: I'd like to see someone try this and post results... does it really work?

 

[tdkkart]

Control joints, in the words of my concrete guy:
"Look at it and think about it, that tube is in solid concrete for 10ft on either side of that joint. If that concrete moves far enough to bust that tubing, it's gonna bust it no matter what you put in there. Gonna bust the tube, AND whatever you tried to portect it with."

He also said, "The only good reason to put mesh in concrete is if you got a bunch of it you need to hide forever. It sure as hell don't do nothing for your concrete". "You want it strong, put in more rebar."

He's right. I've had oppurtunity to disassemble several concrete slabs, wire don't do ****, snaps like string. Rebar on the other hand.........bring your torch.

 

[3x9RT/SE]

Let me chime in here,I did radiant floor heat in my new garage,will have to find that "disappointment"thread to read.I love mine and is very,very efficient!
This is how I did mine,the larger the mass of concrete,the longer it will hold the heat,hence staying off and not calling for long periods of time.I setup my floor to be 6" thick,laid down 1/4" bubble wrap insulation right on the finished ground/grade(also served as the vapor barrier),4'x8' sheets of 10 ga. 6"x6" wire screen,TIED the 1/2" pex tubing every 2' and ran them on 1' centers,with no loop being longer than 250'(I have 5 loops),mounted a elect box during the pour to be finished at surface of concrete with the conduit running back to where my pump station is.This was for the radiant floor temp bulb sensor.Packed it with sand and set the bulb half way in the box and covered with more sand packing tightly.My walls are R19,garage doors are R16,no windows,and R38 in the ceiling.I send 80-85 degree water thru it,and have my slab set on 64 degrees.It calls roughly every 2-3 hours,and when does,it only runs for about 5-6 minutes,thats it!!!And off for another 2-3 hours,I can't tell you how happy I am with this system!!!!!