Good morning all – I live in Atlanta, GA and my house was built in 1999. It’s 3 sided brick but the back is Hardie lap siding that’s seen better days, and I’m going to start replacing it. The back of the home’s sheathing is 1/2″ polystyrene foam board in most places with 1/2″ OSB on the corners and in some areas around window corners, doors, etc. There’s no house wrap underneath the siding since I don’t think it was code required with polystyrene board making up 99% of the sheathing.
My question is – as I replace this siding, I to do what’s best. Is there any issue with me covering the entire back of the house with a house wrap prior to installing the Hardie lap siding? I know that’s standard practice for OSB sheathing but will there be any issues covering up the polystyrene as well? Won’t cause a scenario where it’ll actually allow moisture to build up?
Appreciate the advice!
Replies
Here are a couple details showing a wall and a roof assembly. The roof assembly has two layers of WRB's with XPS in between called out by the architect. The upper layer is called out as ice and water shield which is vapor impermeable. For my two cents, only one WRB is doing anything, the outer layer.
The wall detail shows the WRB only over the wall sheeting, not the XPS. I think there is a reason they only have one called out, because if an Windows, doors, pentrations do leak due to caulking upkeep delays etc, it will create a trough that water cannot easily escape or dry from. That said, if an additional outer WRB layer is installed properly in all regards, and is vapor impermeable, it will stop any water from coming in past the XPS. If you are going to use house wrap a second time, make sure it is not vapor permeable so that it does not allow any moisture in between the two layers.
I'd ask though, do you have reason to believe the WRB under the XPS is not done correctly? If not, I would not use a second WRB. If so, then you can use a second WRB to protect your wall sheeting but invest in a WRB that does not allow anything to pass through such as a self healing peel and stick wrap like Gecko.