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
stool first.

Your window frame has rust on it? Most metal types are aluminum.
wrote in message
ups.com...
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.