Mattock, C.
1991
Canadian Housing Information Center (CHIC).,Technical Series 2000-120
| Research Program
The research looked at different types of EIFS construction and assessed their ability in general to control rain penetration and the flow of heat, air and water vapour. It also looked at fabrication, quality control measures, potential problems and possible solutions. A literature review and discussions with builders, subcontractors, suppliers and consultants formed the basis of the research.
Findings
The durability of EIFS appears to depend on the system's design, workmanship, quality control during the construction process and subsequent maintenance. Known EIFS failures have been attributed, almost without exception, to either faulty installation (the vast majority) or faulty detailing. At the time of the research, no national standards had been established for the correct application of EIFS.
Moisture has been a major contributor to EIFS failures.These failures primarily consist of moisture Findings deposition on the substrate, with subsequent softening, delamination or warping of the substrate. Some drywall manufacturers are now producing moisture-resistant fibreglass-faced gypsum sheathing board and cementious sheathing boards. Moisture in contact with base and finish coats over prolonged periods of time can also cause softening due to reemulsification of the acrylic. Sills, parapet tops and so forth should be metal flashed, steeply sloped or given a special sealer for protection. Moisture may also accumulate at horizontal joints, causing reemulsification.
Moisture-related deterioration may be exacerbated when claddings are installed over substrates that are sensitive to moisture. One of the most common substrates in North America is exterior gypsum board sheathing attached to steel studs with screws. (Alternatively, poured concrete, concrete blocks or existing concrete or brick walls may be used as substrate.) In most cases the EIFS cladding is adhered to the face of gypsum sheathing.This type of construction can result in the entire cladding system relying on the integrity of the gypsum core and/or the paper facing of the gypsum sheathing. In instances where no mechanical fasteners are used, as is often the case, any moisture-related softening of the gypsum board sheathing and/or corrosion of the screw attachments of the sheathing to the studs could result in significant loss of integrity of the cladding system.
Approximately 80 to 90% of all systems in Europe use expanded polystyrene foam board, with the vast majority installed over masonry or poured concrete, not gypsum board. In France, failures of EIFS to provide suitable water and weather barriers resulted in the development of a national performance standard for EIFS, as well as training and certification of installers. This and other related steps eliminated most of the problems of poor workmanship experienced in France in the early years of using EIFS. |