We are considering laying radiant heating coils on an existing slab on grade. What is the minimum capping slab that will allow this? Would you recommend a gypsum product or cement based? Any recommendations for insulation under the tubes?
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Any recommendations for insulation under the tubes?
Does that mean there is none under the existing slab?
Are the walls up yet?
Worst case, unknown, or, no 'R' under existing, walls already stood and DW'ed:
Clear DW 1" above new floor, replace with wood product for "lost" mud forms. Use 1/2" foil faced waterproof foam, foil up, foil tape all joints. The foil won't add to the R value but it is vapor-proof and will give a little help in spreading the heat.
Use thick fin type heat system.
Gypsum: 1 1/2" thick if used. Gypsum is used to hold and spread heat but must have a strong, stiff overlayment. 3/4 ply under wood, cork, <=4" tile, etc. Wonderboard type underlayment under larger tiles
Concrete: 2 1/2" minimum with dialectrics between remesh and aluminum. Ready for any flooring.
No walls? Vapor barrior, 1 1/2" W/P foam, 3 1/2" 'crete, pin to existing under planned wall plates. Polish new slab in prep for acid staining.
In any case, you'll have to think about air sealing the concrete until it cures to prevent cracking and curling.
If you do acid stain, you'll want to keep the air seal visqueen from contacting the curing 'crete. Whatever you use for that will leave it's pattern in the stained colors. Straw patterns, sawdust patterns, wood chips, shavings, leaves, glass, steel, burlap, silk ? ? ?
SamT
A Pragmatic Classical Liberal, aka Libertarian.
I'm always right!
Except when I'm not.
Edited 9/9/2009 6:01 pm by SamT