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Old 05-25-2012, 09:54 AM   #1
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Basement wall XPS insulation with furring strips


I'm going to be finishing my basement, and I've pretty much decided for sure on doing a layer of 1.5" XPS rigid foam insulation with furring strips and attaching drywall to te furring strips, as it seems to be the best method for avoiding moisture damage.

What I'm not clear on is the idea of using tapcons to attach the furring strips through the XPS into the concrete. Doesn't that make a path for moisture to go right through the insulation into the wood?

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Old 05-25-2012, 10:47 AM   #2
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Basement wall XPS insulation with furring strips


Yes, but it's not significant since it forms somewhat of a seal with itself. If it bothers you there are many options for sealing over the holes. You can put some silicone on the nails before driving them. Caulk, tape, etc. I went with XPS glued and taped to the wall and full 2x4 construction for my walls. This provides the best seal short of spray foam, but it robs you of space and is extra work. Are you planning to run electrical through the XPS?

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Old 05-25-2012, 01:21 PM   #3
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Basement wall XPS insulation with furring strips


I will need to run a couple outlets and some speaker wire, but I think I can do that by using 2x3 furring strips and low profile boxes. I want to use the furring strips to save space and money mostly (I have a lot less room than I'd like). It's a home theater and I'll be soundproofing it, which means in this case two layers of drywall decoupled from the studs using clips, and (at least the way I'm envisioning it) having furring strips attached to the exterior walls used as the studs and not having them actually meet the ceiling joists, I wouldn't need to use the clips or double drywall on those walls because there won't be any sound transfer through the studs to the joists above.
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Old 05-25-2012, 05:18 PM   #4
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Basement wall XPS insulation with furring strips


Two other questions, do I tape the seam prior to putting the furring strip on, and where do I screw into the furring strip, it seems like in all the pictures they are screwing right into the middle of the board, but won't that mean the screw is ending up in between the two sheets of insulation, rather than going through them to secure them to the wall?
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Old 05-25-2012, 06:23 PM   #5
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Basement wall XPS insulation with furring strips


You're securing the strip. The strip is securing the foam.
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Old 05-25-2012, 06:34 PM   #6
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Basement wall XPS insulation with furring strips


Most people tape before. If you're looking for a better seal, you'll want to overlap tape after. Going to use a lot of tape though.
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Old 05-26-2012, 12:10 AM   #7
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Basement wall XPS insulation with furring strips


You'll need foamboard adhesive on the side touching concrete to stop any room air from condensing on the cold concrete. http://joneakes.com/jons-fixit-database/743 Caulk under the foamboard and sill sealer under the wood for an air/capillary/thermal break there. http://www.greenbuildingadvisor.com/...-building-code Use the scraps on the rim joist, install with caulk/canned foam for an air seal there, also. http://www.buildingscience.com/docum...l_seal_rev.pdf

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Old 05-26-2012, 08:13 PM   #8
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Basement wall XPS insulation with furring strips


I appreciate the help guys.

This is the first I've heard of the sill sealer under the wood, do you cover that side of the wood with it then shove it on, then?

I'm planning on using 4x8 square edge sheets of Foamular or Styrofoam, will the the adhesive support the weight of the foam board while I do the prepping and drilling on the furring strips, or do I need some more hands? I'm assuming I should do 3" furring strips in the middle of each board as well on the seams so I end up having 24" oc "studs" for the drywall to attach to, should I attach the middle strip first to hold up the foam boards, then cover the seams after, or vice versa?

Also what about the fireblock? Do I just attach a 2x8 or whatever directly to the top of the foam board on the rim joist and the furring strips?
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Old 05-29-2012, 07:25 PM   #9
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Basement wall XPS insulation with furring strips


Quote:
Originally Posted by MrAngles View Post
I will need to run a couple outlets and some speaker wire, but I think I can do that by using 2x3 furring strips and low profile boxes. I want to use the furring strips to save space and money mostly (I have a lot less room than I'd like). It's a home theater and I'll be soundproofing it, which means in this case two layers of drywall decoupled from the studs using clips, and (at least the way I'm envisioning it) having furring strips attached to the exterior walls used as the studs and not having them actually meet the ceiling joists, I wouldn't need to use the clips or double drywall on those walls because there won't be any sound transfer through the studs to the joists above.
You can install the clips to the furring channel, just select the right screw. Thinnest clip + channel combo is 1 1/8"
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Old 05-30-2012, 03:44 PM   #10
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Basement wall XPS insulation with furring strips


Ted White!

I was hoping that since the furring strips and the drywall attached to it won't be connected to anything but concrete that soundproofing on those walls would not be needed?
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Old 05-30-2012, 03:55 PM   #11
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Basement wall XPS insulation with furring strips


Hi. Can the ceiling drywall be lowered a bit and extended all the way to the concrete or block? Then sealed to the block? Otherwise there will be a gap between the top of the foundation and the ceiling drywall. That gap will allow flanking sound up, up and away.
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Old 05-30-2012, 05:06 PM   #12
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Basement wall XPS insulation with furring strips


I don't think I want to down quite that far. Hopefully this not to scale crude drawing in paint will explain what I was planning.


So obviously the problem here is that sound will get through the one layer of drywall on the wall and travel up and around the decoupled double drywall and through the floorboards. I should add that I was planning on adding a couple layers of drywall between the floor joists as well, is there anything else that I can add that would seal up that area better without adding to the width of the wall?

How about a soffit? (Came up with the idea as I was doing the drawing) A double drywalled soffit with insulation inside could block it off couldn't it? I realize now that I have a water drain pipe right in that corner anyway, so I may have to do that either way.
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Old 05-30-2012, 05:16 PM   #13
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Basement wall XPS insulation with furring strips


I really appreciate the way you're taking the time to think this through. The weak area at the top is onl part of the issue, as your diagram demonstrates. A soffit would shield that gap very effectively if that was our only weak point.

The real issue is the single layer of drywall itself. The entire wall is onlt shielded by a single layer of undamped drywall. Some frequencies will easily make it through one sheet of drywall and not be affected by that low-density foam.

A second layer of drywall and damping compound would remedy this. Install the wall furring at 24" centers. If the furring could extend 1/2" past the foam, that would be really great, as this will allow that drywall to flex more freely. More flex = more damping.
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Old 05-30-2012, 05:45 PM   #14
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Basement wall XPS insulation with furring strips


Well I really appreciate you taking an interest and giving your input. To be honest, this being the fourth house I've lived in, and the first one with a basement and a actual spot for a dedicated theater room, I kind of feel like my whole life has been leading up to this point, so I'm taking it pretty seriously. That said, I also have a wife and kids, so every once in a while I get pulled back to reality and try to find ways to cut costs on it.

The plan is for the furring strips to be at 24" oc, and they will be directly on top of the foam, so there will be 1-1/2 inches between the drywall and the foam.

What if I cap the foam and furring strips with double (or more?) drywall behind the soffit, and seal the edges with acoustical sealant?

I'll have to look into the what possible moisture issues there might be with that, but being above grade I'm hoping there wouldn't be much of a problem?
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Old 05-30-2012, 05:52 PM   #15
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Basement wall XPS insulation with furring strips


There's still a small gap. Can you completely connect the double drywall pieces that you have now? There's that little vertical piece on the furring.

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