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NovaBiele 11-10-2012 01:26 PM

Proper Insulation/Membrane for basement walls.floor
Hello everyone! I'm looking for some advice on my basement remodel as I seem to have a situation I haven't been able to find an answer for.

Some background:
The house was built in the mid 60's and I have been living in it for 3 years now. It seems at some point there was water 'issues' in the basement that have been professionally addressed with a retrofit french drain and some outdoor measures as well. Since I have lived here, there has been no bulk water problems at all. The basement will however get pretty humid in the summer & we have used a de-humidifier.

I'd like to remodel about 80% of the ~800sq ft space into living space and would like to mitigate any possible chances for water/mold. Reading through the forums and the building sciences website I think I have a decent plan, but I don't feel right about one issue i'm having with the french drain retrofit. There is a membrane associated with the french drain protruding a few inches from the poured concrete floor around the perimeter of the entire basement:

Here is a cross-section of how I plan on dealing with it:

So I was wondering what everyone's thoughts were about using the 6 mil poly to bridge the membrane gap under the bottom plate of the perimeter walls? There will be an air gap that i don't think I will ever be able to avoid because of the existing membrane!


NovaBiele 11-19-2012 02:34 PM

Anyone have any comments?

I'm getting ready to start ordering materials after the holiday, and would really appreciate some feedback.

I'm a bit concerned about that air gap around the existing membrane.

Also, The Delta-FL installation directions do not mention any XPS. I'd like to avoid using it (height clearance issues) but if it is at the expense of a very cold floor do to poor insulation I'd reconsider. My finished flooring will be some form of synthetic carpeting (over 5/8 OSB over Delta-FL).

I'v also decided to use a sill foam insulation between the poly & bottom plate 'just in case' water penetrates it will not wick up.


Beepster 11-19-2012 03:05 PM

Do you have water issues or a cold concrete floor? I am in the middle of finishing of my basement and am not doing anything besides carpeting the floor. All my landscaping has been dealt with and I have no water issues.

Also, I went with 1" XPS. I monitored the humidity levels over this past summer and was not or the 40-50 % humidity so the smaller sheet was not an issue. Obviously 2" would be better, but for $$$ and space constraint I went with 1".


NovaBiele 11-19-2012 03:54 PM

There hasn't been any water issues since i've owned it. We've had some pretty bad rains...the kind where there is standing water in my shaded back yard for a few days and the basement has stayed dry and I have never noticed the sump pump running. I did need to move the sump piping at one point and it was full of water, so it must have been running at one point.

The basement does get very humid in the summer. We run a dehumidifier with a 50% duty cycle to keep it bearable.

The floor gets pretty cold in the winter, I've walked on it barefoot no problem, but my wife cant stand to. I feel like the DeltaFL air gap + OSB + padding + carpet would be enough but was just totally guessing at this.

Trucon01 11-19-2012 08:10 PM

Off topic question... Where can I get that black dimple / drainage board? I've only seen online where I can buy it in bulk when I only need about 30ft or so...

gregzoll 11-19-2012 08:53 PM

Insulate & air seal your Rim & sill spaces. Also if the windows are original, replacing them will also help with the hot & humidity. Do you have any ducting feeding that space now, to help & heat & cool?

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