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XPS Basement Wall Insulation Tie into French Drain

XPS Basement Wall Insulation Tie into French Drain

Old 08-22-14, 09:27 PM
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XPS Basement Wall Insulation Tie into French Drain

Frequent site reader, but first time poster.
I'm having an interior drain put around the perimeter of my basement walls. The lip of this is spaced 3/8" off the wall and rises slightly up off the floor. The contractor wanted to install a 90mil 0-perm vapor barrier that ran the full length of the wall and was cemented into the drain. I declined this because I think the concrete needs to "dry to the inside" as many posters have pointed out citing various references (building science mostly).

My plan is to install 2" XPS, glue to wall (with the foamboard specific stuff, vertical stripes of glue ... or fasten with those plastic fasteners, where do you get those?) tape the seams, etc. I'll also end up spray foaming the rim joist which will likely seal the top. The foam will control any water that gets through and direct it into the drain lip on the wall.

I'm seeking opinions on:
- Should I DryLoc the walls before I put the foam on? I can't decide given the pros and cons I've found.

- How to interface foam to the drain lip so any water that seeps through the concrete will run into that drain lip. Is there a specific flashing available? Do I set the foam on top of the lip? Notch the foam over the drain?

Here are two pictures of the Water Guard system that's going in to give you an idea of the lip I'm talking about (and a pic where that vapor barrier that I opted not to have).

Thanks for your time!


Old 08-23-14, 12:13 PM
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Join Date: Jul 2008
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If water is passing through the walls, Dryloc is worthless. You never mentioned why the system is being installed, in the first place.

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