I'm preparing to replace Stucco of my old house with new Jame Hardie siding. After the stucco removed, I'd like to add 1 inch rigid foam to enhance the insulation because of the old 2x4 wall not enough in cold weather. Some saying the DuPont Tyvek wrap underneath the rigid foam, but my old house has black tar paper under the stucco. Which order should I go as: tar paper -> rigid foam -> Tyvek wrap, or tar paper -> Tyvek wrap -> rigid foam? Thanks!
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2Is there a reason you want to keep the tarpaper at all? Also, are you using faced or unfaced foam?– ThreePhaseEelCommented May 9 at 2:09
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Probably I'll use the faced foam, which could be another question. Yes, the tar paper will be mostly ruined and I thought it can give extra water proof (thicker than Tyvek and "oily") and need be replaced too, which should be part of the question. If it is not providing extra protection, I'll get rid of it. Thanks a lot!– YifangtCommented May 9 at 2:37
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1 Answer
The felt (tar paper) will probably be full of holes and tears anyway, so I'd probably remove it. It's not doing you any good behind the foam, either. If that's difficult for some reason, leave it. Felt breathes to some extent, so it's not likely to be a problem.
As for the foam and housewrap, the house wrap should be just under the siding. It acts as a "drain plane" for liquid water that may get around the siding, as well as a windblock. Foam will eventually absorb such water, so you want to protect it.
Use plastic cap-head nails of adequate length to minimally install the house wrap. Seal the seams with approved tape (not whatever you have laying around--it probably won't last).