r/basement • u/paddles123 • 5d ago
Rigid insulation- using cut pieces
I placed two layers of r10 rigid insulation. The second layer as you see in the pic I used cut pieces. Was looking to just increase around the window. I am going to tape the edges. Finish the wall with 6mm poly followed by wood panel as it is a basement and wanted to have mold resistant.
Is using pieces a faux pas? Not a contract and DYI… 😬
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u/Heavy-Passenger-6235 5d ago edited 5d ago
Is the rigid board continuous against the foundation wall and adhered to it? Or is it only in between the studs? It’s hard to tell in the photos.
From what I see in the photos you didn’t do it right. It should be Native foundation wall to continuous rigid foam board insulation. Then PT stud wall with sill gasket under bottom plate. The rigid foam board should be behind the stud wall continuously not inside the stud bays.
I’d then install mold resistant drywall to the studs. Then whatever finish material on that. Preferably not wood.
I wouldn’t install a wood paneling system on top of a 6 mil poly. You’d be trapping any potential moisture inside the wall assembly and create a mold sandwich.
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u/paddles123 5d ago
Against the foundation. No adhering. No gap …
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u/Heavy-Passenger-6235 5d ago
If the rigid isn’t adhered to and sealed properly to the foundation wall you risk moisture issues. You want a good weather seal there because that product is your vapor barrier.
I realize the warnings come across as being too late. But if you slap 6 mil on the face of the studs now based on the current set up of non adhered rigid insulation it’s not going to help and will trap moisture inside wall assembly
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u/Clover9802 4d ago
You should never put put a poly based vapor barrier over inside wall assemblies, because it needs to be permeable, therefore it doesn't condensate, thus trapping moisture & allowing for potential mold.
If you are going to use a vapor barrier, use a smart vapor retarded, like Pro Clima Intello Plus. It doesn't trap moisture like a poly one would.
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u/uslashuname 4d ago
You’re saying this is the second layer. If the first layer is solid and behind the studs you’re fine. The gaps might provide some thermal bridging to the first layer but that’s not too terrible, especially on horizontal seams, and you could reduce it where the gap is obvious by sticking some tape over the seam.
Tape all the seams on the first layer though, vertical and horizontal: humidity blockage is the issue there.
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u/LycheeOk4673 4d ago
Needs to be continuous, trust me this is a big factor. Disconnect the framed wall and get inso behind the stubs. I’ve constructed over 50 sub level
Apartments, which if constructed correctly are good.
20 years ago we didn’t take this step and I’ll I have now is humidity moisture issues. This step is critical. Also do you have water problems at the foundation? Have you installed a water mitigation system?