Replies

1. 
   Guest_ | Sep 19, 1999 12:47am | #1

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   Hi Marc,

   After you have compacted the stone, add a sand buffer of about 1 inch, lay your poly on top of it, next your sm and then finish with the re-enforcing and tubing.

   Gabe

1. 
   Guest_ | Sep 19, 1999 08:16pm | #2

   *Marc, The ideal sequence is vapor barrier (for ground moisture), expanded polystyrene insulation,2-3" of sand/gravel (w/fines and medium aggregates for ease of grading), #3 rebar 24" on center (Will keep tubing much "flatter") Placing the sand gravel above the insulation provides both additional thermal mass and allows for absorption of bleed water from concrete. Pouring directly onplastic or insulation generates excessive bleed water on the surface of the slab,weakening it's durability. It also contribute to the slab "curling", or developing high points.ABSOLUTLY place expansion material at the perimeter of the slab or you will see the floor buckle when you turn on the heat. Speaking as a concrete finisher having done many of these. Good luck, Rick

1. 
   Guest_ | Sep 19, 1999 08:27pm | #3

   *Marc. Gabe did make a very good point about a layer of sand beneath the rigid insulation, just enough to provide a level base to lay it down on. Uniform thickness of the slab is a better deterent of cracking than increased thickness. it also aids in keeping the tubing at a uniform distance down from top of slab 1 1/2" - 2" down.

2. 
   Marc_Sillars | Sep 19, 1999 11:13pm | #4

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   Rick,

   Thanks for the great advice. I will use it next week. This is what makes this site a great source of inforamtion and people like you make the site great.

   thanks again

3. 
   Marc_Sillars | Sep 20, 1999 03:24am | #5

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   I will be pouring new basement slab (7' below grade) with radiant heat with the proposed construction. 4" stone,2" insulation and 4" concrete. PEX tubes attached to wire mesh on top of insulation. I am considering adding a Vapor barrior. If so should it be on top or below insulation? If on top won't wire mesh and walking on it tear it up?

4. 
   Guest_ | Sep 20, 1999 03:24am | #6

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   Hi Rick,

   While I appreciate the finisher's viewpoint, adding a layer of permiable material between the VB and the concrete will invite water to infiltrate and render the VB useless. This will cause the slab to sweat forever.

   Gabe