Basement insulation for irregular corners

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Cba76
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Basement insulation for irregular corners

Post by Cba76 » Sun Oct 07, 2018 11:16 am

Hi all, first time poster after watching the YT video about how to insulate a basement with rigid foam. I’m about to undertake this project but have one huge dilemma: the corner of my basement are rounded, they don’t come to a point. As such, I can only place a rigid foam board about 3” away from either side of the corner and still have it lie flush with the wall. What should I do in the corners? Is it a big deal to have a few narrow strips of rigid foam that aren’t exactly flush with the wall but are taped and sealed with expanding foam?

Other question I have:

1) do I need plastic barrier on the inside of my stud wall?

2) does the wood for the toe bird of the stud wall have to be treated? Does all the wood of the stud wall have to be treated?

Thanks!!!
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Corner of my basement
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Shannon
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Re: Basement insulation for irregular corners

Post by Shannon » Sun Oct 07, 2018 12:12 pm

You can use some narrow strips to make the corner and seal them up.
Depending on the rules your local codes follow most areas will still require a air/vapour barrier installed before the drywall. Some may have exceptions if you used 2" foam but you would have to check with your local inspection office.
The bottom plate should be either standard lumber separated with a foam type gasket or poly strip of plastic sheeting or it should be a treated piece of lumber. If you use treated lumber you must use the proper fasteners for ACQ treated lumber to attach the studs. All the rest of the framing can be standard untreated lumber.
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Cba76
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Joined: Sun Oct 07, 2018 11:09 am

Re: Basement insulation for irregular corners

Post by Cba76 » Sun Oct 07, 2018 12:23 pm

Thanks Shannon, very helpful! I’ve seen so much conflicting advice on vapor barriers in basements. Will it hurt at all by installing a 4-6 mil sheet of plastic over the studs? Any drawbacks, apart from having to do it?

Ok perfect, so untreated toe board is ok as long as I put a plastic barrier between it and the concrete, that’s great to hear.

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Shannon
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Re: Basement insulation for irregular corners

Post by Shannon » Sun Oct 07, 2018 12:27 pm

Air vapour barriers must be a approved type not just standard 6mm poly. Ask for approved air vapour barrier poly when you purchase. There are new hybrid ones now that allow breathing when conditions are right in the abasement as well, thats what I will use in my next basement job.
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