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Securing pex to insulation board

bobFlor
bobFlor Member Posts: 15
Has anyone ever secured pex to foam board using duct tape. Mesh is not really for structure in my case and staples are just as costly. Tape seems to make so much more sense . but I haven't tried it yet . just wanted to put it out there and get some feed back

Comments

  • bobFlor
    bobFlor Member Posts: 15
    To update my project status. I have only four inches of depth  to work with . I could only find one inch insulation on the market. I now have three inches for concrete . I don't have a huge budget . I want pex in the slab . I thought what if I just taped it down with the same tape I used to seal all the insulation with. Why not
  • Zman
    Zman Member Posts: 7,542
    I have never tried it. I would be concerned that it would lift during the pour.
    The system will perform better with the tubing in the center or the slab, on mesh.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • pecmsg
    pecmsg Member Posts: 4,677
    I ASSUME there's wire mesh going down correct?
  • Dave H_2
    Dave H_2 Member Posts: 545
    The mesh is not meant to withhold a structural load, it is designed to minimize the cracking of the concrete. Concrete all by itself is wonderful in compression (put heavy stuff on it), but without the wire mesh, concrete doesn't like expansion and can crumble.
    Now that you are looking at only 3", the wire mesh will seem a little more critical and now at this point, its not the cost of a product to perform a single function, now it has a dual purpose.

    The tape will not hold, the pex is going to want to move all over the place and it will win taking the tape with it.

    If I had my way, I would staple the tubing down to the foam, then lay the wire on top, it eliminates the dual purpose.

    One rule I follow when it comes to concrete is it is always easier, cheaper, simpler to do what you want with concrete BEFORE it cures. After the fact, it will always cost twice as much to do it right the second time!

    Dave H.
    Dave H
    ChrisJCanucker
  • Jamie Hall
    Jamie Hall Member Posts: 22,874
    I'd go with @Dave H_2 . There might be a temptation to raise the tubing a bit off the insulation, but I think not -- too hard to get the concrete under there. Duct tape is wonderful stuff, but as he says, it won't hold and you'll have no idea where the tubing got to. Wire the tubing to the mesh every couple of feet and it won't wander off somewhere.

    Do use mesh. I'd go even farther on that thin a slab and use fiber reinforcement in the concrete mix as well.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • bobFlor
    bobFlor Member Posts: 15
    OK guys thanks . that was fast responses. One thing though . is putting the mesh over the pex a bit dangerous for the pex . how does that work. 
  • Jamie Hall
    Jamie Hall Member Posts: 22,874
    Won't hurt either the PEX or the mesh, helps keep the PEX down where it belongs.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • pecmsg
    pecmsg Member Posts: 4,677
    They make clips that twist onto the mesh to prevent rubbing 
  • GroundUp
    GroundUp Member Posts: 1,862
    What type of space is this and why do you only have 4 inches to work with? Can't you dig out more dirt and do it properly? This is one of those things where you either pay now or pay later but rest assured you WILL pay more in the long run if you get cheap now. You should have a minimum of 2" of foam underneath and around the perimeter. Cutting that in half will drastically increase your energy usage during operation
  • hot_rod
    hot_rod Member Posts: 21,790
    edited October 2021
    it’s really not hard to put the tube in the very best location, 2” below top of slab. Very easy to tie tube to mesh and raid the mesh with chunks of foam. So now the tube and the mesh are where they belong. I used a 6x6 #4 mesh which is a much heavier wire gauge and does provide some reinforcement. Especially in the slab
    wire ties, bar ties, and wire really to tie down
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Zman
  • bobFlor
    bobFlor Member Posts: 15
    So . I should really lay down another inch of insulation first . then , 2 inches of concrete is OK over mesh and pex.
  • bobFlor
    bobFlor Member Posts: 15
    I'm OK with putting down one more inch of insulation .  its the depth of concrete pours over the mesh and pex that I don't know so much about.  if I  add the fiber and have the mesh in there  with the pex . tied to it . will I be OK with 2 inches of concrete.
  • bobFlor
    bobFlor Member Posts: 15
    To go back to Ground up question sorry , its a two story cape with just an old concrete floor in it . there was never a vapor barrier or any insulation under our feet for the last 15 years . just some wood floor some linoleum and some tile. I hammered all of that out after putting in sill plates new 2x6 walls . I got the doors up 41/2 inches and did perimeter in 4" x1" 1/2 insulation . 
  • hot_rod
    hot_rod Member Posts: 21,790
    You want 1-1/2 times the aggregate size over the tube. Typical concrete is 5/8” stone, so at least 1-7/8”, call it 2”. If you use a 3/8 pea gravel mix 1-1/8” and add extra fiber for those thinner pours 

    one problem with fiber is the finish, it will look like it is covered with dog hair 😉 unless you power trowel to melt the fibers. But not an issue if you cover it

    for a garage slab at least 3-1/2” pour
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream