Why does the top of a rough opening (bottom of header) need to be wraped in plastic?
The bottom and sides make sense to me (although I have switched to using Jambsills for the bottom and self-adhesive stick on flashings for the sides), but doesnt wrapping the bottom of the header create a “bucket” instead of an “umbrella?”
Best answer I’ve gotten from anyone so far is – “don’t know, that’s the way we always did it.”
Replies
It doesn't, according to the flashing article in the latest issue of JLC. The detail there is to tuck the flange under the housewrap at the head, and also to use a piece of Vycor or similar adhered to the sheathing above the opening and extended down over the flange. It's worth reading that article and/or seeing his demos at the JLC show. A good detail in most respects IMO.
It doesn't make sense housedktr, just like a lot of stuff the window gurus will tell you.
This makes sense to me: if you are letting water get behind your siding, you are doing something wrong....fix the siding!
blue
I've learned not to assume the siding is keeping all the water out, no matter who put it up or what kind it is.
It isn't that the housewrap is supposed to wrap up under the header... it's just supposed to extend down over the nailing flange or the Z flashing at the head of the window. If you wrap the housewrap down under the bottom of the header (and I do just that), you're supposed to slice it and slide either the flange of the window or the Z-flashing up into the slice, so the housewrap ends up overlapping the window flashing.