Ponessa had some thoughts about stucco that I want to
share with you.
is professor emeritus of housing, indoor environment,
and health at Rutgers Cooperative Extension.
got in touch after I wrote an article about a lawsuit by
the Commonwealth of Pennsylvania against an area
developer over stucco issues with new homes.
had mentioned EIFS — Exterior Insulation and Finish
System — which had been widely used in the 1990s and
early 2000s but was the source of major lawsuits over
poor installation — failure to follow manufacturer’s
instructions — resulting in mold and mildew problems.
said research conducted mainly by Building Science Corp.
in Massachusetts in the late 1990s identified the causes
of EIFS failures.
traditional cement-based, three-coat stucco systems have
been used successfully in both wet and dry climates for
many years, the more modern, synthetic two-coat products
are not as durable, he said.
inevitable cracking or poor detailing around
penetrations has allowed water intrusion, which is
disastrous in wet climates, Ponessa said.
other issue involves synthetic stucco’s interaction
with underlying water barriers.
at Building Science Corp. revealed that, unlike
cement-based stucco, the synthetic formulation interacts
with water barriers — building paper, felt, or
housewrap — to destroy their water-repellent
properties. Water coming through the stucco penetrates
and enters the wall cavity.
solution that researchers identified is simple: Use a
second, "sacrificial" layer beneath the
can even be cheap building paper, Ponessa said. The
double layer solves the main problem.
are a few more details and caveats, but this is the
essence of the problem," he said.
an old story.
had been used successfully in commercial applications
since the 1950s, but it was cheaper than the old
three-coat system and, well, you know what happened.
what I always say about reading directions.