Proper installation methods for synthetic stucco on buildings
Here we provide a photo guide to some common leak points on EIFS stucco building exteriors, to aid in the the inspection, diagnosis, repair, and proper installation of synthetic stucco EIFS systems.
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When originally imported from Europe to the United
States in the 1970s, most exterior insulation and finish systems
(EIFS) were “barrier” type systems. They were designed
to create a waterproof exterior skin consisting of a
thin layer of acrylic polymer-based synthetic stucco directly
applied to foam insulation.
Our photo (left) shows a modern Sto-Wall covered home that was investigated to diagnose the sources of wall leaks through the stucco system. We found many installation details that did not follow the manufacturer's recommendations. As a result there were significant leaks into building walls and a considerable mold contamination issue as well.
The expanded polystyrene
(EPS) foam was glued to the building’s sheathing.
A layer of fiberglass cloth embedded in the synthetic
stucco provided reinforcement, and a thin acrylic finish
coat added color and texture.
With the EPS glued directly to the sheathing, there
was no place for building paper or conventional flashings
at penetrations. Openings, joints, and penetrations relied
on caulks and sealants for waterproofing. With no backup
waterproofing or drainage layer, there was little margin for
error.
While these systems performed adequately in Europe
for nearly 25 years, the United States version had thinner
base coats and lower polymer content, creating a weaker
skin. Also, workmanship in the United States was often inferior
due to lack of applicator training and quality-control
programs.
The water running down this building interior wall was traced to omission of the manufacturer-specified sealant methods at the top of the building exterior wall. Wind-blown rain entered the wall top just below the soffit overhang, wet the wall interior cavity, and finally appeared on the foundation walls below.
When water leaked into these systems through
failed caulk joints, cracks in the stucco skin, or through
the window frames themselves, it wet the foam insulation,
sheathing, and sometimes the structural framework.
Below left, our EIFS leak point photograph shows a leaky window detail at an EIFS-clad building in New York.
This
in turn led to more sealant failures and cracking of the surface
and additional leakage. The EPS foam acted like a
sponge, trapping water against the building, and the nonporous
polymer coatings retarded drying. In many cases
the leakage and resulting decay was extensive, resulting in
widespread property damage and litigation.
Above right, our EIFS leak point photo shows leak stains on the L-channel securing the end of a soffit covering over an upper level intersecting roof. Water entered the building wall at that glob of foam in the center-left of the photo,and if you look closely you may also see leak stains down the stucco wall at center right of this picture.
Below left, our EIFS leak point photograph shows that the builder relied on caulk at a roof-EIFS-wall intersection to try to stop leaks into the structure.
Above right, our EIFS leak point photo shows that the roof-wall step flashing was improperly sized and placed, allowing leaks into the structure.
Below left, our EIFS leak point photograph shows a crack developing in an EIFS wall coating.
Above right, our EIFS leak point photo shows a similar crack in the EIFS coating below a roof edge - a likely building leak point.
Below left, our EIFS leak point photograph shows a drywall screw used to attach a gutter strap, violating the manufacturer's EIFS installation guidelines, puncturing the wall, and creating a possible leak point.
Above right, our EIFS leak point photo shows incomplete EIFS coating and repair work, leaving the fiberglass mesh exposed and leaving a hole in the building wall.
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Thanks to Michael Leavitt, an professional home inspector, for help with the EIFS resource links.
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
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Class Action Settlement for Senergy and Thoro brands of EIFS was completed the Superior Court of the State of North Carolina, Hanover County
"Weather-Resistive Barriers [copy on file as /interiors/Weather_Resistant_Barriers_DOE.pdf ] - ", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
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