I have a window that was installed in a stucco wall years ago that
leaked. When the stucco was torn away around the window today, the
contractor said it leaked because the tar paper was installed wrong. It
went in front of the metal fin rather than behind it, according to him.
(It also was installed poorly with numerous tears and not much coverage
of the metal fin) Is he corrrect? Should the tar paper go behind the
metal? Seems like the metal would be left to rust that way.
negative batman. tyvek, caulk the window flange, install the window, seal
entire nailing flange with window tape (flexseal flexwrap whatever its
called) then siding then caulking. the only part of the tyvek that overlaps
the flange would be the top.
You are exactly right. Before all of this flashing tape came out, we would
cut 30# felt into 12" strips and tack around the window. Our procedure was
felt paper on the sheathing, moist stop on the sill, bead of caulk on the
back of the nailing fin, window installed, nail through every hole in nail
fin with 2" roofing nails, strip of 30# felt tacked across the bottom, strip
tacked up each side (overlapping bottom piece), strip tacked across top
(with sheathing felt rolled back down over the top piece. Now, we use the
flashing tape and tyvek in lieu of the felt paper. I actually prefer the
felt, but the flashing tape won't stick to it worth a damn.
An unfortunate common misconception is that the nailing fin is flashing.
What robson described, though practiced daily by most framers, is grossly
Just my .02
The (I may mis spell this) Protecowrap product will stick to the felt just
fine. Place it and roll with a J-roller. It seems like it isn't sticking.
Two days of sunshine and you can not remove it.
OTH, it does not seem to stick quite as well to the Tyverk product. It does
but not as well.
I may have to try that. I'm not completely sold on housewrap. Not much
can beat felt. I've pulled off siding that has been on for 40 yrs, and the
felt behind it looked as good as new. Time will tell if the housewrap is as
The purpose of the housewrap is to let the house breathe while preventing
water intrusion. Sort of like "Gore-tex" for houses. Felt will trap
water vapor inside the house, making your insulation less effective.
Bob Morrison, PE, SE
R L Morrison Engineering Co
Can't imagine tearing away a stucco wall and the metal mesh without damaging
the "tar" paper.
Don't know about tar or felt paper. We always used something the boss
called moist stop. Black and rubbery, somewhat shiny, no line markings on
it. Came in rolled sheets about 3 foot wide. This was laid in the window
stool, edges cut just enough so the remainder would drape below the window.
Any other additional covering for water or vapor covered that.
Seen similar lately but has adhesive backing, and is not nearly as wide.
This is sorf of like tape. Procedure is to lay a band across the bottom,
then both sides, then the top. Water can't get under it when traveling
downwards this way. You should still lay some form of moist stop on the
Your window frame has rust on it? Most metal types are aluminum.
To answer your question YES he is right.
As others have pointed out there is more to a proper install than that. But
there is no way it could be considered marginally correct if the paper was
over the fin.
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