Help framing basement

6 years ago

Hello - we’re looking to frame and finish our basement, but have this strange drain system around the entire perimeter of the basement that catches moisture from the walls (see pictures). It’s my understanding that basement framing should be flush to the wall, so I have no idea how to go about framing this? Do I have to cut a curve in the bottom of every stud and use narrower bottom plates (2x2)? Are we forced to build the frame further away from the wall (if that’s possible?). We want to preserve as much space as possible as our basement is already small.

Also, we have this crazy septic tank pipe that jets out over a foot from the wall, any idea how to elegantly deal with that?

Pls help!

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Comments (4)

PRO
GN Builders L.L.C
6 years ago
last modified: 6 years ago
Put a wall in front of it, it's ok to be away from the wall.

Something like this.
worthy
6 years ago
last modified: 6 years ago
Air space between the insulated wall and the foundation wall invites condensation and should be avoided.

Your interior weeping tile system is not all that unusual. However, it poses a problem of how to install water impervious insulation. Normally, you would simply attach rigid foamboard such XPS (extruded polystyrene) with concrete fasteners, then frame over that. But it looks like the membrane on your wall was painted over; penetrate it with fasteners and you'll be reducing its efficiency. You could experiment with foamboard adhesive.

Spraying the existing wall with ccspf is an alternative. But it's expensive and you'll be out of the house for a day due to fumes.

No need to notch the 2x4s if you put 1.5"-2" thick foamboard on the walls. When I finish basements, I always put 1'' thick strips of XPS under the bottom plate to reduce the chance of rot from minor leaks and the upward drive of moisture through the floor.

As for the septic pipes, cut the insulation as close as you can, then use handheld expanding polyurethane foam sealants, such as Great Stuff, to fill the gaps.
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Home Repair
Original Author
6 years ago
Thanks guys. What’s on our walls is a CleanSpace Wall, which is a vapor barrier. It’s not pain, it a think plastic sheet that covers all the walls. This is raising another question - can we even insulate over a vapor barrier?
worthy
6 years ago
last modified: 6 years ago
I don't see the problem, as any water is supposed to drain between the CleanSpace barrier and the wall, according to this posted video.

The only finicky thing will be getting the foamboard to stay tight between the framing and the Cleanspace, as shown in the first post above. Be prepared to temporarily brace the foamboards, then shim them to achieve a tight fit. It doesn't have to look pretty.

To make the job easier, look for the largest foamboards--4'x8' XPS. Just checked and I see some Home Depots carry both Owens Corning and Dow brands in that size.

You can leave the bottom part of the wall, where the Cleanspace slopes to cover the drain, un-insulated. Most of the energy loss is at the top of the basement wall where it is above grade.

The rim joist area should also be insulated with foamboard and sealed with expanding polyurethane foam.

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