Replies

1. GBA Editor
   Martin Holladay | Apr 30, 2014 05:37am | #1

   Dennis,
   Here are two choices:

   1. From the bottom up: 9 inches of EPS rigid foam, polyethylene, 5 inches of concrete.

   2. From the bottom up: 5 inches of sand or crushed stone, 4 inches of rigid foam, polyethylene, 5 inches of concrete.

2. 
   DennisDipswitch | Apr 30, 2014 07:14am | #2

   I know that Lstiburek has addressed a few things regarding slabs,fill and poly.Am I correct in thinking the poly always goes directly beneath newly placed concrete?

   My concern with using fill at all is that the moisture within it would always remain and never be able to dry in either direction...but I guess fill located in the ground in a climate that has rain will always have a fair moisture content?

   Would termite treatment be essential to the fill in this sandwich?

3. GBA Editor
   Martin Holladay | Apr 30, 2014 07:26am | #3

   Dennis,
   Q. "Am I correct in thinking the poly always goes directly beneath newly placed concrete?"

   A. Yes. (Some concrete contractors have different opinions. Be prepared to stand your ground.)

   Q. "My concern with using fill at all is that the moisture within it would always remain and never be able to dry in either direction, but I guess fill located in the ground in a climate that has rain will always have a fair moisture content?"

   A. Of course, all layers under your poly can't dry upward. That's normal. In your case, there will be some sideways drying, because your fill will be in contact with your above-grade concrete stem walls.

   Q. "Would termite treatment be essential to the fill in this sandwich?"

   A. Termite issues (and termite infestation prevention details) are intensely local. Get local advice on this question.

4. 
   DennisDipswitch | May 01, 2014 05:12pm | #4

   Would I want to continue the poly up the foundation wall?

5. GBA Editor
   Martin Holladay | May 02, 2014 08:52am | #5

   Dennis,
   Q. "Would I want to continue the poly up the foundation wall?"

   A. Assuming that the concrete foundation wall will extend above the height of the new slab -- and it sounds as if it will extend 10 inches above the new slab -- then the answer to your question depends in part on how you intend to insulate and finish the concrete wall that extends above the slab; what type of wall will go above the concrete wall; how the framed wall above the concrete will be insulated; and how you intend to detail the transition between the concrete wall and the above-grade framed wall.

6. 
   DennisDipswitch | May 02, 2014 09:43pm | #6

   I intend to place foam vertically from the foam beneath the slab to the top of the concrete foundation.or higher,framed wall to be insulated with fiberglass batt insulation,1" rigid on outside of plywood sheathing on framed wall.Floor to wall transition(where vertical foam is) to get tiled and capped.

7. GBA Editor
   Martin Holladay | May 03, 2014 05:02am | #7

   Dennis,
   There is no harm in bringing the polyethylene up vertically against the rigid foam on your concrete wall; nor is there any harm in omitting it. Either way is fine.

8. 
   DennisDipswitch | May 03, 2014 06:37am | #8

   Should there be any consideration on how to address how the top edge of the vertical foam is terminated/capped/sealed?

9. GBA Editor
   Martin Holladay | May 03, 2014 06:49am | #9

   Dennis,
   You want to maintain continuity of your insulation layers. The insulation layer of your framed walls should be as continuous as possible with the insulation layer at your concrete wall, with no gaps or thermal bridges. If necessary, these layers can be overlapped at the area where these two insulation systems meet.