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Old 05-30-2011, 02:40 PM   #1
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pouring a 2 inch concerete cap

I want to put in-floor radiant heat tubing 1/2 pexalpex on top of an existing garage floor. My plan is to lay down 1/4" foil bubble insulation on top of existing floor with the tubing on top. I would also drill in rebar anchors on a foot grid and tie horizontal re-bar into those and pour over....Head room prevents more than 2" of new concrete....any problems with this process?


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Old 05-30-2011, 02:47 PM   #2
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I would be worried about 2" thick concrete cracking and so forth. Why not float an engineered floor with some flex in this situation?


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Old 05-30-2011, 02:52 PM   #3
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If there is going to be cars on this floor I would be worried about the 2 inch cracking because of the bubble insulation underneath. The insulation couldn't support the weight of a car and would just crush, I would expect.
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Old 05-30-2011, 02:59 PM   #4
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Seems like a lot of work to go to for heating, and yes I would be concerned with cracking.

If there is an exterior wall, why not a PTAC unit mounted in the wall? Or a mini-split unit - a little more money but even easier to install? Both are heat/cool all in one unit.

I have a PTAC in my garage (finished and now used as a hobby room for my wife's sewing/quilting and my ham radio / electronics tinkering). And planning to use a mini-split for a master bedroom addition this summer.
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Old 05-30-2011, 02:59 PM   #5
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You cannot successfully install rebar in a concrete floor less than 4 inches thick. The problem is the lack of cover. ACI requires a minimum of 1-1/2 inches clear cover on top of the rebar, and 2 inches clear cover if the concrete touches soil. With a two inch thick slab, this is obviously impossible.

Should you install rebar or wire mesh, the anticipated result will be rusting of the rebar or mesh, with ensuing expansion of the metal, followed by cracking of the concrete.

You can install a 2 inch concrete floor without rebar, you may want to consider using fiber concrete to reduce cracking.

If you plan to continue to use the garage for vehicle storage, you would certainly want to rethink using bubble insulation. As previously noted, this would certainly compress, and possibly break, under normal garage type loading.
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Old 05-30-2011, 04:04 PM   #6
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On top of all that good advise, bubble wrap is as useless as boobs on a bull. If you don't have lots of insulation under the existing slab, you are going to heat the Earth more than your garage. If you are not going to have vehicles in the garage, or maybe even if you will on occasion, consider an inch of rigid foam, then the plywood that is pre-grooved for PEX, then more plywood over that. Paint the plywood and go to work. Or, like mentioned, just deal with a cold floor and have a different kind of heat source. Wearing felt pack boots or tennies and extra socks is pretty cheap and easy.


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