Source: Basement Insulation Systems, Yost & Lstiburek, Building Science Corp.

is it possible to find only the corrugated plastic

Yes. Delta FL. This foregoes the insulation, but saves you some headroom if that's important.

can I simply put down 6 mil plastic over the concrete and lay ply/OSB over that as the subfloor?

This will trap moisture under the poly--at least until it finds its way through the nail/screw holes etc into the layers above it.

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This is not a recommended method. But in many of the new homes I have built, I have glued down synthetic low pile carpet directly on the concrete without an underpad and have not experienced mildew/mould problems. But this was over 6" of freeflowing gravel and 4"-5"concrete. And I keep a dehumidifier (or two) running year-round.

Thanks, Worthy.

From reading previous posts and topics, you mentioned your preference for framing before the flooring. The diagram you posted seems to suggest the opposite. The way I see it, the two options are these (forgive the crude drawings):

Option 1: Frame on the subfloor

Option 2: Frame on concrete

I like option 1 because I think it offers any vapors under the Delta FL a place to go (conceivably -- if the vapors can actually condense and travel down into the French drain).

I like option 2 because it makes changing the subfloor possible in the future if that's ever needed. The downside with option 2 is that I have to provide a perimeter for venting, which will require me to get creative with carpeting.

So is my rationale sound for preferring option 1? Thanks again for all the help.

Zayd

That BSC diagram shows the wall framing on top the plywood floor. But I've never seen any technical reason for that sequence.

Delta's installation instructions specify that the material should be as tight as possible to the walls and then sealed with foam. BSC also calls for a tight fit. Both the XPS and the Delta have sufficient permeance to permit vapour to pass through.

The BSC diagram illustrates an Enka drain, but no gap. Your first post doesn't mention a pre-existing French drain. These are usually put in to handle exterior water leakage or water under the slab, as in the BSC diagram.

Got it -- thanks.

Does my rationale for Option 1 make sense? I do like the fact that the vapors can go somewhere. And the Platon material I plan to use claims impermeability to vapor, so it seems this would be important.

the Platon material I plan to use claims impermeability to vapor, so it seems this would be important.

As I mentioned in my earlier post, the Platon is not impermeable. From the Delta website linked above:

"Though the air in the living space is completely isolated from the system, DELTA-FL is designed to allow small amounts of water vapor into the room to maintain a healthy humidity level."

The pic below from Building Science Corp. Digest 103 Understanding Basement, shows the wall framing in place before the floor.

Thanks.

One last open question as I think through this. The finished floor, and therefore the Platon/subfloor, will butt against an interior block wall along one side of the finished area. Since there will be no French drain along that wall, I don't want to let the Platon vent into that area. Should I seal off that side somehow at the Platon? If I don't, the Platon will vent behind the stud wall that will be I front of that block wall.

The Delta FL should be sealed tightly with silicone or low expansion foam wherever it's butting up to other material.

Here is a link that might be useful: Delta FL Installation

Thanks.

One last open question as I think through this. The finished floor, and therefore the Platon/subfloor, will butt against an interior block wall along one side of the finished area. Since there will be no French drain along that wall, I don't want to let the Platon vent into that area. Should I seal off that side somehow at the Platon? If I don't, the Platon will vent behind the stud wall that will be I front of that block wall.

Thanks, Worthy. Your advice here is truly appreciated.

I'll follow up with after pictures once I'm all done (not sure if I took before pictures!)