To vapor barrier over tar paper walls?

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Joined: Mon Jul 01, 2019 6:55 am

To vapor barrier over tar paper walls?

Post by offroader » Mon Jul 01, 2019 7:15 am

Hi guys, great site and great work on youtube Shannon. So I have a 1972 built raised bungalow in Barrie Ontario. It's a walkout basement because the house is built on a hill side. Cinder block foundation, interior wall insulation is tar paper glued to cinder block and nailed firring strips over top, 1" rigid board between strips then gypsum board overtop. No studded wall with insulation.

I removed the drywall off two of the sections, other sections the drywall remains, realized the situation and want to re-insulate the whole basement but on a budget. Plan is to not put the drywall back up in those specific sections, 2x4 stud the whole basement, roxul and drywall. I have already tuck taped all seems and blocked air passage ways. Question is, do I need to put vapor barrier over the roxul before drywall or will that create a double vapor barrier and create a mold situation?

I am not in a position to remove everything, add rigid board or spray foam.

Thanks for any advice.

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Re: To vapor barrier over tar paper walls?

Post by Shannon » Mon Jul 01, 2019 8:21 am

Well even with the rigid foam most areas will require you to still install vapour barrier before drywalling. The exception for some areas would be if the rigid foam was 2” thick or more and continuous and sealed . In your case this does not sound like what you have so I would say you will need the air/vapour barrier. Check with your local building code authority to be sure.
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