Understanding EIFS

As most practitioners in Canada may be aware, the Ontario Association of Architects, through the OAA Indemnity Plan, is directly indemnifying its members for practice in Ontario. The accumulation of funds over the decades provides the necessary assurance (and insurance) for architects in good standing with the OAA. Recently, the Council of the OAA decided to apply for a licence to own and operate an insurance company to carry on the business now operated by the Association through its Indemnity Plan. This will put the program on a more secure footing, place it under the control of the insurance regulator, the Financial Services Commission, and help manage the exposure of the Association in the event of a catastrophic loss. The indemnity managers must always be wary of risks associated with various design practices employed by design professionals.

There is a reported increase in the number of claims concerning certain wall assemblies that utilize the face-sealed approach to exterior wall enclosure. As such, the OAA Council decided to exclude higher-risk wall assemblies from its indemnity coverage. This exclusion was planned to be in effect by July of this year. Other exclusions for acts of war and terrorism, as well as claims on mold were also approved.

Among the face-sealed wall assemblies that the OAA is seeking to exclude from its indemnity coverage, some specific usages of traditional EIFS (exterior insulation finish systems) are among the prime candidates. EIFS that have been supplied and installed as the major component of a face-sealed wall assembly, where the exterior face is assumed to provide a perfect barrier to rain penetration and without any secondary protection, are recognized as having greater risks associated with resistance to water penetration. The magnitude of such risk increases with severity of both the climate and building exposure, particularly when face-sealed systems are installed over water sensitive assemblies (e.g. wood or steel studs with sheathing). The OAA has issued the OAA Rain Penetration Control Practice Guide, which provides a technical understanding of the issue and suggests appropriate methods of designing effective wall assemblies using various wall materials, including EIFS. The guide is posted on the OAA Web site at www.oaa.on.ca

Most experts would agree that face-sealed systems are at a higher risk for the occurrence of water penetration. This risk, of course, is not limited to EIFS-clad buildings. Other types of face-sealed systems can also be problematic in the management of water ingress, such as many conventional window-wall systems or pre-cast concrete panels installed without two-stage rainscreen joints.

First developed in Europe in the 1940s, conventional EIFS came into the North American construction industry in 1969. However, it was only in 1993 that proprietary EIFS incorporating both drainage strategies and a second line of defence were introduced in Canada, and later in the United States. It is generally acknowledged that EIFS installed since that time in accordance with rainscreen principles are performing satisfactorily.

As drainage-type EIFS systems were more widely used, it became more common to pay closer attention to the details between the EIFS and the adjacent elements, such as windows, waterproofing, sealants and other cladding elements. Invariably, most credible experts on EIFS will admit that water penetration problems with EIFS-clad walls typically occur at such interfaces. There is no question that the quality of the EIFS rendering will affect the performance as well, but the interface details are a significant consideration, and many face-sealed EIFS installations from the 1970s and ’80s where adequate attention was given to these details have performed successfully.

While drainage-type systems reduce many of the potential problems associated with moisture penetration, face-sealed EIFS (also referred to as “barrier” EIFS) should not be considered intrinsically flawed. The selection of the substrate (for example, the moisture sensitivity thereof; consider the difference between gypsum sheathing and concrete masonry substrates), building exposure, climatic loads, and the complexity of the faades and the resulting interface details are some of the factors to consider when assessing the risk in selecting any wall system, including face-sealed EIFS (see CA, April 2001).

The escalation of litigation, warranty-claims, and insurance claims in the construction industry over the last decade is widespread across North America. This litigious activity is far-reaching, reflecting many aspects of building envelope performance–or failure. Many architects have selected and adapted various building materials and systems the true limitations of which were not properly understood. After EIFS were introduced to North America, the insulation component was often attached directly to a sheathing-type substrate, either wood or gypsum (in Europe, the systems are typically installed over masonry substrates). Water entering through joints and other interfaces would often be trapped long enough for damage to occur to the sheathing and framing. The susceptibility of these systems to high moisture loads is considerable, often resulting in decay of the concealed substrates.

The popularity of these systems increased throughout the 1990s. A common assumption is that as the popularity of EIFS increased, the rigours of design were relaxed and the general quality of construction decreased–a phenomenon reflected in the earlier comment that more litigation occurs in the construction industry today than ever before.

To summarize, a number of issues lie at the core of many of the problems surrounding EIFS: a lack of understanding the potential vulnerability of face-sealed systems; the lack of attention to detail by design professionals; ignorance of and/or disregard for good workmanship; and inadequate field review and supervision during construction. These phenomena are not exclusive to EIFS. Lessons learned from the leaky condo failures in the Lower Mainland of British Columbia should remind us all that simple disregard for good design and construction practices, rather than inherent material properties, is often at the root of most water penetration problems in exterior wall systems.

Materials and assemblies are not conscious beings, but they do have properties. It’s up to design professionals to develop the expertise to use materials and assemblies in accordance with the limits of their respective properties. EIFS, when drained, is fine in most applications, but face-sealed EIFS, even with good details, should not be used over substrates vulnerable to water damage. With proper attention to detail, selection of substrate, and careful consideration of building exposure and climatic issues, architects in Ontario–and the rest of Canada–can be assured that EIFS will remain a viable cladding for many buildings in the years to come.

Kevin C. Day is Associate & Building Science Specialist in the Toronto office of Morrison Hershfield Limited, and Pierre E. Gallant, OAA, MAIBC, MRAIC is Principal & Manager of Morrison Hershfield Limited in Vancouver.