Moisture patrol

Latest technologies and proper installation can help prevent moisture penetration in EIFS applications
August 11, 2010

Stephen Klamke feels somewhat vindicated. A recent study by the National Association of Home Builders (NAHB) Research Center has positively concluded what the executive director of the EIFS Industry Members Association (EIMA), Morrow, Ga., has been telling the commercial construction industry for years: Most moisture problems associated with exterior insulation and finish systems (EIFS) have been caused not by the products themselves, but by improper installation and application.

In fact, the study takes the assertion one step further, stating, "Exterior claddings, including brick, stucco, vinyl siding and exterior insulation and finish systems, all have the same potential for damage if weather barriers, flashings and opening protections are not used or are installed incorrectly."

During the late 1980s and early 1990s, the market for EIFS saw phenomenal growth, a result mainly of the energy efficiency, durability and versatile design possibilities offered by the systems in comparison with other claddings. But when lawsuits started flying from disgruntled building owners with wet and warped walls, many people in the commercial construction industry found it more convenient to blame the EIFS product than faulty construction practices.

"After four years of shouting this from the rooftops, independent research has borne out what we have known all along: that not only are there no inherent moisture problems with EIFS, but virtually every cladding system is vulnerable to moisture problems if improper construction methods are used," adds Klamke.

Proper installation

Although the majority of moisture-intrusion cases have been in residential projects, subsequent doubts cast on the products have carried into the commercial segment.

"Moisture damage is not so common in the commercial construction market because you have professionals writing up the contract documents, which are fairly specific on which products can and can't be used, and the proper methods of sealing doors, windows and other openings. Then you have the extensive field supervision used in commercial construction," says Klamke. "These factors simply don't exist in most residential construction, so it is more prone to failure."

To avoid such problems, most building teams will only work with the most highly qualified subcontractors to do the EIFS application, says Robin Savage, vice president of Birmingham, Ala.-based contractor Robins & Morton. Such attention to detail was evident in the construction of the Gerald Champion Regional Medical Center in Alamogordo, N.M. (featured in Building Design & Construction, June 2000). The one-story, 151,770-sq.-ft. facility utilized a combination of EIFS and traditional stucco for cost-effectiveness, durability and energy efficiency, and was designed to withstand Alamogordo's extreme temperature and humidity swings.

"Throughout the project, we paid extra attention to details," adds Savage. "We made sure the edges were caulked and sealed properly, and we also made regular inspections. We made sure the entire application was done in accordance with manufacturer recommendations."

Water intrusion

With EIFS, says Klamke, water most frequently enters at windows, frequently through the joint around the perimeter or through seams and joints in the window assembly itself.

To avoid moisture penetration around the windows, EIMA suggests cutting the insulation board in an "L" pattern to de-crease base coat stress at the corners of wall openings. Edge-reinforcing mesh should then be installed around the perimeter of the window, followed by small strips of mesh placed diagonally — called butterflies — at each corner over the edge-reinforcing mesh.

The most common type of EIFS is a barrier or face-sealed system, which consists of an insulation board made of polystyrene or polyisocyanurate foam that is secured to the surface of the exterior wall with adhesive or mechanical fasteners. Fiberglass mesh is then installed for added strength, followed by a water-resistant base coat and an acrylic copolymer finish coat.

Drainage EIFS

More recently, EIFS manufacturers have responded to water-intrusion problems linked to the barrier system by introducing EIFS assemblies with drainage capability. Unlike barrier systems, the new systems allow water that gets behind the wall system to exit before damage can occur. The drainage medium is most often a fastening system involving a mesh material, or with grooves extruded into the foam board.

"Some saw the development of drainage systems as tacit admission on the part of the EIFS industry that there was something inherently wrong with the barrier product," says Klamke, noting that it was actually an effort by the industry to protect building owners when approved installation procedures were not followed.

Another growing EIFS technology involves an adhesive that acts as a secondary weather-resistant barrier. A number of EIFS manufacturers have developed adhesive secondary barriers to replace paper, plastic or felt weather barriers, and they have shown a great deal of promise.

Manufacturers agree that it makes sense to be able to combine the adhesive, which bonds the expanded polystyrene insulation board to the wall, with a secondary barrier that helps prevent water intrusion. At least one firm has developed a product that involves applying a liquid-membrane secondary weather barrier and an EPS adhesive in one step. Such products allow building owners to have a secondary weather barrier, whether required or not, at no added cost.

A similar product was used for the recent completion of a 12-story, 90,000-sq.-ft. addition to the Crawford Long Hospital in Atlanta. The product is also seen as offering more desirable negative wind-load characteristics.

In many cases, building teams working with a secondary barrier consisting of felt or plastic feel they must attach the systems with fasteners. However, testing shows that EIFS have a better negative wind-load performance if they're adhesively attached. Many specifiers and builders, therefore, believe this type of system is definitely a plus, especially in coastal areas where wind loads are of great concern.

Standing the test of time

Regardless of the industry's skepticism toward EIFS systems, it's clear that these novel developments and the product's track record in the United States make EIFS a suitable choice for a range of commercial applications. The latest NAHB findings, as well as improved EIFS systems and installation methods, help lay to rest the nagging doubts and myths about the product's performance.