I am in an argument with builder over flashing.
(I have got religion and have read many
threads, articles, videos, etc. on flashing)
Here is the wall spec: stick framed with sheathing
and covered by an inch of polyiso, aluminum windows,
then rainscreen of 1“ strapping and hardipanel.
Q1: If we use housewrap to add some extra protection to the
drainage plane, does it go over the foam or under it?
Q2: Is there any reason why a wooden nailer frame must be
built out to the thickness of the foam, around the window,
which the nail flange would go over?
Replies
Hmmm... on the housewrap. Would be best over the foam I think, mostly to incorporate the proper weave sequence with the window flashing
I don't punch the window frame out, just attach the nailing fin over the foam and wrap.
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Weave sequence, huh? That was the concept I was grasping
for in my mind.On the subject of punching out, around here, since siding is
usually very heavy (at least half inch ferrocement instead of
quarter inch like hardipanel) there is a great deal of concern
about downward creep in the outer skin of the foam, resulting
in screws in your rainscreen being bent downward also, and
horizontal gaps opening up in the foam.As a result, a few builders lay the foam panels horizontally
and put in nailer strips of the same thickness between courses,
and along the bottom and tops of walls. Kinda like a Mooney wall,
only on the outside. Then the rainscreen screws on perpendicular to the nailers.
They've got a special beefed-up screw for this they call a
"foam screw."
With that siding situation, I think I would put the foam on the interior
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You can do that in Maine, no doubt, but here the climate is like Arkansas, so the foam has to be outside.
Too late to consider SIPS?
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Ohmygod here we go with the dread SIPs!!! It shows up in
every thread, it seems, like a disease.I spent hundreds of hours researching SIPs and figuring the
whole thing out, but in the end it came down to a tangled
set of interlocking constraints involving the lender,
code approvals, manufacturer certification, and engineering.
In short, they wanted me to ditch my architect and hire
a new firm, SIPs specialist, and pay 300 mile travel fees
on top of that.I came to the conclusion that, given the degree of
thermal bridging that is still inherent in SIPs--especially
here, where they require 4x4 splines--simple foam on the
outside of stick-framed is more energy efficient and
cost effective.