Jim,

Some fluid applied membrane roofing systems such as Masters Choice "Patchworks"
use a polyester reinforcing fabric as a substrate to span open seams or small
holes/voids.  Manufacturers literature says that openings up to 2 inches can be
spanned in this manner.  The reinforcing fabric is embedded into the first coat
of compound while wet.  The New York Landmarks Conservancy, working with the
National Park Service, sponsered a very successful stabilization demonstration
project on one the buildings on the south side of Ellis Island last year and
used these materials to reline copper gutters.  The gutters had developed a
pattern of evenly spaced holes where the (acid?) rain wash was channeled by the
ribs of the clay roof tiles.  As a patch repair technique this is anticipated to
have a service life of at least 7-10 years.

Lisa Sasser

-----Original Message-----
From:   JRhodes <[log in to unmask]>
Sent:   Tuesday, October 12, 1999 4:18 PM
To:     [log in to unmask]
Subject:        Re: FW: [forum-l] metal shingles

Re: Ellen's elastomeric coatings and "all the crevices of metal shingles"

I've seen satisfactory performance of applied coatings on copper roofs
which had developed "pinholes" in undocumentable locations.  But I have
trouble imagining how thin elastomerics (thin enough to not obscure the
roofing pattern very much) effectively span seams or gaps, especially when
even small movements of the substrate could  tear open the membrane.  That
is to say that if the elastomeric is well bonded to each of two metal
pieces, as it should be, then movement between those two pieces stresses
the inner face of the membrane with zero dimension of tolerance.  The outer
face of the membrane might stretch a bit, but doesn't the inside face of
the membrane propigate into a tear?!  Therefore, I wouldn't expect much
from thin coating seamed material subject to expansion, contraction or
other movement.  Thick sloppy bituminous coatings are another thing, and
that would considerably obscure the pattern considerably.

It's the same principle as for joint sealants that are bonded to all three
concealed faces of the joint (instead of only the two opposed faces).
Movement or opening of the joint would tend to tear open from the inside
out, causing the joint to fail.

I assume coating a shingle roof is a stopgap measure to keep from a more
thorough repair or treatment.

--Jim
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