Let’s say you’re building a house with plywood or OSB sheathing. You plan to install 2 or 4 inches of rigid foam on the exterior of the wall sheathing, followed by vertical rainscreen strapping and siding. Where does the housewrap go?
Depending on who you talk to, you get two different answers:
- It goes between the rigid foam and the vertical strapping, or
- It goes between the sheathing and the rigid foam.
I’ve heard a variety of arguments in favor of each position. For example, I’ve heard that the housewrap belongs between the foam and the strapping, “because that way it’s easier to integrate with the flashing at the logical drainage plane.”
On the other hand, I’ve heard that the housewrap belongs between the sheathing and the foam, “because that way it protects the sheathing,” or “to prevent the housewrap from flapping in the wind,” or even “to protect the housewrap from extreme temperatures which might degrade the plastic.”
Both sides of this argument have merit. If you have a strong opinion favoring either position, it’s safe to say that either approach can work well, as long as the housewrap is properly integrated with all of the window flashing, door flashing, and the flashings protecting other penetrations.
Simplifying the decision
If this quandary has you discombobulated, though, here’s an easy way through the thicket:
If you’re unfamiliar with the innie/outie terminology, an innie window’s flanges are in the same plane as the OSB or plywood wall sheathing, while an outie window’s flanges are in the same plane as the back of the siding. (For more on this topic,…