ACADEMIC STUDY ON SYNTHETIC STUCCO PERFORMANCE RELEASED:
"94% OF BUIDINGS SHOW MOISTURE LEVELS SUFFICIENT FOR STRUCTURAL DAMAGE"
HOUSTON, TEXAS (October 4, 1999)… A major academic study focusing on the performance of synthetic stucco -- technically referred to as Exterior Insulation and Finish Systems (EIFS) -- in residential and commercial buildings in the United States has been released by Dr. Charles Graham, Professor of Housing Research at the Department of Construction Science at Texas A&M University in College Station, Texas.
The study, which included an extensive literature review and detailed field investigations of 17 buildings in three different climatic regions of the United States (Houston, Denver and Chicago) 1, found "16 of the 17 (94%) buildings in this study had leakage that could support damage to the structural systems, given enough time. Almost every wall inspected with EIFS on it had leakage." (page 5-2)2
Consistent with previous research, Dr. Graham’s study found surface barrier design EIFS can pose serious water entrapment problems, even when installed according to the manufacturers’ specifications. While the study reports that "the primary damage mechanism is water leakage behind the EIFS which supports
Some of the report’s more interesting documentation of damage includes:
• Photos of large mushroom-like fungi (nearly one-half a foot in diameter) growing inside the upstairs bedrooms of EIFS homes in both Houston and Chicago. (Figure 6; photo enclosed). According to the report, these were discovered growing on the inside spaces of these homes in an area in which a great supply of water was getting into the wall cavities. The homeowners in Chicago noted that they could hear water running in their walls when it rained.
• Photo of a Denver church in which woodpeckers had pecked large holes through the EIFS exterior siding (Figure 38). Dr. Graham uses this example to illustrate the inadequate thickness of the EIFS coating which, in this study, averaged just 1/10" of an inch. Woodpeckers are but one of many threats to EIFS: weed eaters and errant baseballs have also been known to penetrate the EIFS surface, leaving a ready opening for water intrusion.
• Photo of a home which had the EIFS literally ripped off of it during a hurricane in South Florida (Figure 5). According to the report, "EIFS do not perform well when there is either the danger of lofted debris (missiles) or pull off during wind storms." (page 5-12) This type of damage lead the Metro Dade Building Code Compliance Office to establish stringent guidelines for the use of EIFS in the area, the most extreme of the requirements being the "large missile test" which requires the structure to withstand the impact of a two-by-four fired from a cannon at 34 miles an hour. (page 2-8)
The report lists several design and construction problems associated with EIFS including the following:
• Failure of caulk sealants
• Failure to install slopes on horizontal surfaces exposed to weather
• Unsealed penetrations through EIFS (to accommodate utilities, etc.): report identifies a 51.7% moisture reading3 near one such penetration
• Inadequate clearance between bottom edge of EIFS and soil: report identifies a 22% moisture level in a home with this problem
• Inadequate clearance between roofing materials and EIFS
• Inadequate coating thickness
In his report, Dr. Graham concludes:
"Even when an EIF system is installed according to the manufacturer’s instructions, however, damage can still occur. It is the combination of materials, equipment and appurtenances in the wall system that make up the building envelope and it is at this system level where all of the pieces are combined that failures often occur (e.g. water leaks). Therefore, it is at the cladding system level that surface barrier design EIFS fail to deliver satisfactory performance. Redundance for water leakage, which is a statistical probability on all buildings, is not provided in the surface barrier design systems. The loss of redundancy exacerbates the potential for problems when materials such as OSB sheathing, plywood sheathing, gypsum sheathing, wood framing, steel stud framing and the fasteners of all of these are subjected to constant water leakage." (page 5-12)
Dr. Graham cites several experts (including an EIFS industry executive) who agree that water infiltration into any exterior siding is inevitable. He goes on to say that EIFS’ "failure to provide redundancy for leakage on the building envelope is a major drawback for surface barrier design EIFS." (page 5-11)
The report advocates using the same guidelines for EIFS applications as for masonry or wood clad exteriors, which include a cavity with a moisture barrier behind it. Dr. Graham notes that the new EIFS drainage plane systems provide these features, adding that "pressure equalized rain screen designs that ventilate the wall would be preferable in most applications of EIFS." (page 5-11)
The report, in numerous instances, compares the U.S. application of EIFS with the European model, in which the EIFS is applied over a masonry substrate. He notes:
"Use of EIFS over masonry structures incorporating mass storage wall system designs would work as well in the United States as in Europe. Concrete masonry units, clay and concrete brick, clay tile, concrete and other similar non-deleterious materials could be used effectively as substrates for EIFS in mass storage designs. The design flexibility and
energy efficiencies of EIFS could then be incorporated in masonry and concrete wall systems that incorporate the European experience and knowledge base about such systems." (page 5-12)
3 Moisture content in building between 5% and 12% is considered normal or at equilibrium with their environment; 13% to 19% is within the cautious zone where wood rot may be possible; and readings of 20% and are generally considered at high risk for decay. (page 4-7)