Vapor barrier behind tub surround?

joenorm | Posted in General Questions on September 5, 2019 01:20pm

Hi all,

Plumbers are installing a tub/surround unit so I am putting some craft faced batts behind before they get to it

Should I put polyethylene on as a vapor barrier as well? I was at the lumber yard and a builder told me this would be a good idea.

thanks

Answer

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MALCOLM TAYLOR | Sep 05, 2019 01:32pm | #1
Joe,

Where are your air-barrier and vapour-retarder located on the rest of the exterior walls?
joenorm | Sep 05, 2019 02:45pm | #2
Malcom,

I am taping the seems of the ply and using tyvek for WRB. Still haven't pulled the trigger on exterior foam but i'd like to.

Interior I figured would just be drywall with latex paint.

thanks
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Brian Pontolilo | Sep 05, 2019 05:05pm | #3
Hi Joe,

You are in Climate Zone Marine 4, right?

If you are using the International Residential Code as your guide, look at section R702.7 on vapor retarders. In your area, if you don't meet certain conditions (basically adequate continuous exterior insulation or vented siding), then you would install a class I or class II vapor retarder on the inside of the walls (poly or kraft faced batts, for example). If you do meet those conditions, then you could use a class III vapor retarder (drywall with latex paint). So, you need to decide on exterior insulation really soon.
joenorm | Sep 05, 2019 05:59pm | #4
The batts have a Kraft face, so according to what you wrote that I am already covered.

thanks for the reference, I will try to read through the code.