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How do you get floor heat in the middle of a slab?

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Comments

  • rhl
    rhl Member Posts: 100
    Sorry, to be a dolt, but, my contractor is going to do something to lift the pipes up off off the ground. If you don’t do it using a method like this how the heck do you do it?
  • Zman
    Zman Member Posts: 7,569
    There is a little hook on the back of the concrete rack. It can be used to pull the mesh up as they pour over it. My guess is that they are going to claim that they will pull it up as the go.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • nibs
    nibs Member Posts: 511
    How big are the rooms?
    What is your contractor doing about control joints if needed?
  • hot_rod
    hot_rod Member Posts: 22,120
    rhl said:

    Sorry, to be a dolt, but, my contractor is going to do something to lift the pipes up off off the ground. If you don’t do it using a method like this how the heck do you do it?

    Lifting the tube and mesh is heavy, un-predictiable and tiring work. Maybe for a small under 1000 sq ft job it can be done.
    If you lift too much, the mud gets underneath an you have a crack potential with not enough coverage. not really a viable method.

    There are components made to support rebar or mesh in the slab.

    On engineered projects the product and installation method is shown and clearly defined. A good engineer or firm will inspect a job prior to the pour to assure it is done correctly. I've had some engineers witness the entire pour to be sure it is done properly.

    For a homeowner or small rest job, it comes down to how much energy you want to apply to get it done properly, or the way you want it.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Gordy
    Gordy Member Posts: 9,546
    It’s a method that’s inconsistent, and invites a snagged tube, with possible kinking, or puncture.

    The thinner the pour, the less room for error.
  • rhl
    rhl Member Posts: 100
    The total floor area is about 1000 sqft, it’s about. Essentially imagine a 32 x 32 square, it’s divided into four rooms, however they don’t all have equal size.

    I agree that raising things up seems complicated. What I’m asking for is what to do so that you don’t have to do that. Do you just essentially lay rebar in a grid with 2” chairs ? It seems if you space that stuff closely together, it’s still a disaster.

    Is there any videos or pictures that anyone knows of an install where the pipes are laid down from the get go?
  • Gordy
    Gordy Member Posts: 9,546

  • Gordy
    Gordy Member Posts: 9,546
    The key is close enough centers to eliminate the mesh, or rebar sagging, and pumping up. In other words where you step goes down, and an adjacent section goes up. Road mesh which is heavier gauge is less likely to do this.
  • nibs
    nibs Member Posts: 511
    You could (on a thicker slab) place the first half, possibly with a retarder, then drop the mesh on and tie the pex & place the top. If the pour is small enough and the crew completely ready you would have about two hours between the pours, and still get long chain molecule links between the pours. You would want a very dry mix at first, which of course makes the cement much stronger and less prone to shrinkage.
  • Gordy
    Gordy Member Posts: 9,546
    That would be a nightmare in my opinion. For everyone. Especially the guy doing the pex. Retarder only buys so much time as to not ending up with a cold joint. Especially floor pours where a vibrator is hardly if ever seen.
  • nibs
    nibs Member Posts: 511
    @Gordy have only done my own pex and on mesh only in one room, you guys are the pro's, but have lots of experience in and around concrete.
    On an open slab, you could prefab the mesh and pex and slide it into place, as long as you had a reasonably flat layout area. Can think of a number of scenarios that would work.
    Cement is very predictable and well understood as are rebar and mesh. It is all in the planning, my idea is probably too far fetched to be taken seriously, but have spent a lot of time working out novel ways to save on construction projects. usually with some degree of success.
  • rhl
    rhl Member Posts: 100
    Hey guys, we are now starting to lay down the insulation. We are testing out the chairs. The chairs i have do not have the metal plates on the bottom, they are not very heavy, and about 5' long, they can be kicked around quite easily. What is the recommended way to secure them so they aren't just going to get kicked around? Staple them to the insulation? Tape them? something else?
  • Gordy
    Gordy Member Posts: 9,546
    Use tie wire, and tie to the mesh.
  • rhl
    rhl Member Posts: 100
    You mean put a mesh on the ground ?
  • Gordy
    Gordy Member Posts: 9,546
    The slab bolster goes down first in runs of what ever centers you feel will support the mesh properly. Then lay the mesh, and tie the mesh to the top runner of the slab bolster with rebar tie wire. Then fasten pex to the mesh

    If you are using that cheap thin gauge rolled mesh you will have a fight on your hands. I recommend the heavier gauge road mesh.
  • rhl
    rhl Member Posts: 100
    Right, so this is not addressing my question. what prevents those slab bolsters from getting moved? i wanted to secure them to the ground. I thought there was a decent suggestion, of using the tie wire to tie the bolsters to a mesh on the ground. Then you could forgo to the mesh in the concrete (at the expense of some tensile strength, i was adding fibers to the mesh anyways), and then it also makes one less obstacle for the people doing the pour..
  • psb75
    psb75 Member Posts: 831
    As a 'wet-head', call me crazy but if Hot Rod or Siggy speak...I tend to "stretch an ear" in their direction. And concrete experts are good too. But if you want heat...who ya gonna call?
  • Gordy
    Gordy Member Posts: 9,546
    edited March 2019
    If the mesh is tied to the slab bolster, how can the slab bolster move?. Is your concern about vertical up lift? Securing them to the foam with staples is an option. Seems unnecessary, and the staples probably will work free. The weight of the mesh once installed should hold them in place.

  • Gordy
    Gordy Member Posts: 9,546
    If you have not already purchased them get the style I posted. Not like the ones in your link. They will be more stable, and not push into the foam as easily.
  • rhl
    rhl Member Posts: 100
    i see. they are already on site and without the metal base. i am worried about them being kicked and stuff. we are going to put the mesh on top of the bolsters in the middle of the concrete, however, after a private conversation, we have determined that the fibers in the mesh are far superior at providing tensile strength to the concrete.
  • Gordy
    Gordy Member Posts: 9,546
    edited March 2019
    Yes fiber mesh is. I thought you were using the wire mesh as simply a medium to fasten the pex, and keep the pex in the middle of the slab.