• Full below-grade basement
  • Poured Concrete walls/slab

A few years ago I had major waterproofing done to our basement/foundation. When they did this, they also installed an external dimpled waterproofing membrane across 2 or the 4 walls. From what I know, this helps with drainage towards the footer french drains.

I will begin framing the basement and wanted to know if a moisture barrier (not a vapor barrier as I've learned) is necessary behind the studs on these foundation walls which had an external barrier already applied. I intended on using an insulating foamboard (XPS I believe is the industry name) behind the studs for the untreated basement walls.

  • Required by whom or what? The question is subjective, otherwise. – isherwood Nov 15 '17 at 17:14
  • Unsure. Perhaps I mean "redundant". – Shawn Nov 15 '17 at 17:18
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    I'd consider it redundant, but it partly depends on your situation (whatever precipitated the earlier work) and how well it has performed. Hard to say. – isherwood Nov 15 '17 at 17:19
  • It's performed immensely well. Well enough that I feel confident we can finish the space. – Shawn Nov 15 '17 at 17:21
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    IMHO anything you put on the inside will just hold moisture in the wall and create an environment for mold. Let the wall breathe as amuch as possible and dry to the inside if you get any moisture or vapor penetrating the wall. Good luck! – ArchonOSX Nov 15 '17 at 21:18

I framed in a basement a few years ago and we first coated the wall with dry lock and then hung some thick plastic over the block wall before framing. Water getting to untreated studs is not a good thing. Which leads me to also mention that the bottom plate of your wall frame needs to be pressure treated. Hope my input helped a little!

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