Exterior Insulation and Finish System
Whether EIFS is pronounced, 'ee-fess,' 'eye-fess,' or 'eefs,' the acronym denotes an Exterior Insulation and Finish System. EIFS is an exterior wall cladding sometimes called “synthetic stucco.” Although there is a superficial similarity between EIFS and traditional stucco, they are different building materials with very different installation requirements and very different performance characteristics.
As the name suggests, EIFS combines a finish layer with exterior insulation. EIF systems are a type of “continuous insulation” system. Typically, a continuous layer of foam insulation board is applied on the exterior wall of the house in the areas to be clad with EIFS. A finish coating consisting of a base layer and a finish layer of polymer-modified cementitious material is then applied to the exterior surface of the insulation board. The finish coating is formulated to function as a weather barrier to protect the control layers beneath it.
EIF systems are proprietary systems. What this means is that the components of each manufacturer’s system were designed, formulated, tested, and approved to be installed as a unique system. The components of one EIFS manufacturer’s system are not intended to be used with components from a different EIFS manufacturer’s system.
Although there are some general installation guidelines that EIFS manufacturers may share in common, each manufacturer’s installation instructions are part of the manufacturer's proprietary system. When installed according to the manufacturer’s instructions by qualified persons using appropriate construction techniques¹, EIFS claddings can provide long-lasting, superior performance.
To achieve the desired performance, the installation of an EIFS must be integrated with the installation of other components of the building envelope. The Texas Bureau for Lathing and Plastering acknowledges the importance of the “other components” in its Design Manual: “The successful installation and performance of EIFS cladding is dependent upon the proper design and construction of the adjacent materials and systems of the structure.” Ultimately, the performance of an EIFS is directly related to the experience, knowledge, and craftsmanship of the of the persons who install it. EIFS is extremely installation-dependent.
The critical, “other building components” related to an EIFS may include the air and moisture barrier between the exterior sheathing and the EIFS; the moisture drainage components of the exterior wall, including the drainage plane or rain screen; the flashings at penetrations of the wall; and the application of sealants. Several of these components are typically considered by EIFS manufacturers to be an installation separate from the installation of the proprietary EIFS. The materials and the installation of the “other components” are typically excluded from warranty coverage by the EIFS manufacturer. The typical EIFS manufacturer’s installation guidelines assume an ideal condition on the job site in which there is close coordination between the installers of the EIFS and the other trades that are responsible for the installation of the various “other building components." On the job site, the reality may not reflect this ideal.
Many of the problems that have been associated with EIFS installations do not derive directly from the EIFS itself; they are the result of deficiencies in the installation of the “other building components.”
The correct² installation of flashings, raingutters, and diverters; the correct installation of appropriate expansion and control joints; the correct installation and flashing of transitions between the EIFS and other exterior claddings (such as brick, stone, or siding); the correct flashing of windows, doors, and other penetrations of the exterior building envelope; and the correct use of weather barriers, drainage planes, sealants, and other components of the water resistive barrier and moisture drainage system are critical to the performance of an EIFS.
Several of the components that are critical to the performance of the EIFS will require regular maintenance throughout the service life of the EIFS. For example, the management of rainwater may affect the durability of the EIFS. Raingutters and diverters must be correctly installed and maintained. Many (most!) rain gutters are not installed in compliance with the specifications provided by manufacturers of exterior claddings. Most EIFS installations depend on the correct choice and correct application of sealants at transitions around framed openings in the EIFS plane, such as windows and doors. Sealants at these locations are critical for preventing the intrusion of water into the wall. Exterior sealants are not permanent. Field research on the durability of exterior sealants exposed to weathering has shown that the service life and performance of most sealants in the field study, even those that met the specifications of the ASTM 920 standard, fell far short of performance in real world conditions. Many exterior sealants will exhibit significant degradation within one year of exposure to sunlight and weather in Central Texas. Field tests of 184 specimens of urethane, silicone, and hybrid sealants conducted by the Durability Lab at the University of Texas at Austin resulted in failure of 29% of all specimens within 6 months of exposure: 22% of silicone specimens failed; 39% of urethane specimens failed; 55% of hybrid specimens failed.³
Regardless of the type of exterior cladding, a functional, correctly detailed and installed moisture drainage system must be provided to remove the water that infiltrates the exterior wall cladding. Water will always find a way into an exterior wall. In common with almost every other exterior cladding, EIF systems in residential construction must usually provide a way to remove or allow the escape of the water or moisture that penetrates the exterior cladding. The critical zone seems to lie between the exterior cladding and the exterior sheathing. Water that penetrates into this critical zone must be quickly removed before the layers beneath it are affected, including the structural sheathing and the structural framework itself. The structural sheathings currently in widespread use in residential construction, such as OSB, have a very low tolerance for exposure to moisture and are likely to deteriorate if moisture is trapped within the wall.
Traditional masonry claddings, such as brick, stone, and stucco plaster are not waterproof materials. They are also not water-sensitive materials-they do not typically degrade from exposure to water. Because of their mass and porosity, traditional masonry materials are able to absorb, sequester, and gradually release, through evaporation, diffusion, capillary flow, etc., significant quantities of the water that penetrates the exterior cladding.
In contrast to traditional masonry claddings, the continuous insulation layer in an EIFS is a lightweight, low-permeance material. Similarly, the base coat and finish coat of an EIFS have low permeance. An EIFS does not have the ability to absorb, diffuse, and gradually release moisture that penetrates the exterior cladding like a stone or brick cladding can. Without a correctly detailed, functional water barrier between the EIFS and the structure, and a functional moisture drainage system within the wall to remove the water that infiltrates behind the exterior cladding, water in the wall can become trapped behind the low-permeance continuous insulation layer of the EIFS. Water that is trapped behind the EIFS will inexorably lead to deterioration of the structural sheathing and the structure. Flashings must therefore be correctly installed to drain the moisture that penetrates the EIFS cladding to the exterior. Adequate air space must be provided between the low-permeance exterior cladding and the moisture sensitive, moisture reactive sheathing beneath the cladding. EIFS-clad walls are, in this way, less fault-tolerant of deficiencies in the moisture drainage system than are exterior walls clad in traditional masonry materials.
EIFS has certain advantages in thermal efficiency over brick or masonry veneer walls. EIFS is typically fastened to the wall with adhesives, therefore there is little or no thermal bridging through the wall by fasteners. EIFS exterior walls have excellent thermal efficiency without the mass of masonry, and with thinner wall dimensions.
The best time to inspect an EIFS to assure strict compliance with the manufacturer’s installation instructions, and to verify that the EIFS is correctly integrated with the water barrier and moisture drainage system is during the installation of these critical interrelated systems. Once the installation of an EIFS is complete, many of the critical details at the interface of the EIFS with the water barrier/moisture drainage system may no longer be visible or accessible to inspection. For example, after installation of the EIFS is complete, a visual inspection cannot affirm that splices or tie-ins from the air/moisture barrier are correctly installed over the back leg of flashings, starter tracks, weep screeds, and similar details to form a continuous shingle lap that directs incidental water to the exterior.
At the point that an EIFS installation is complete, our inspection is necessarily limited to a visual survey of the accessible components of the EIFS and the moisture management system. Although this includes inspecting the installation details of the exterior cladding and flashings for visible deficiencies and inspecting the exterior for indicators of its performance, our conclusions may be limited to inferences we can draw from the clues available for discovery during our inspection. EIFS and stucco-type exterior wall systems are inspected the same way as any other type of wall system: using the guidelines promulgated in the TREC SOP. We always recommend that you consult a stucco specialist certified by the Exterior Design Institute for a more detailed evaluation of the exterior EIFS and/or stucco system on the Property.
The performance of an exterior cladding system is an active, continuous, on-going process, not a singular event at a point in time. Accordingly, the most meaningful indicators of the performance of the exterior cladding are more likely to be revealed by observations made over a period of time, under different conditions, from winter to summer, from wet to dry. Our inspection is based on the conditions present on the single date of the inspection.
The predictive value of an opinion formed from an inspection at a single point in time, based on an overall impression of the quality of workmanship at the finish surface, without the benefit of knowledge of the underlying details of construction, may not be as meaningful or as accurate as an opinion that is based on affirmative knowledge of the details of construction and based on observations of performance made over a period of time.
We base our general inspection of the EIFS exterior cladding on our work experience, training, and knowledge. For general guidance, we refer to the Systems Manual 2001 of the Texas Bureau for Lathing and Plastering. We also refer to the technical literature from several EIFS manufacturers, notably that of STO Corporation and ParexUSA, as well as BASF, and Dryvit Systems Incorporated. We chose the STO Corp. and ParexUSA solely at our own discretion, based on our perception of their status in the EIFS industry, the accessibility of their technical literature, and our impression of its thoroughness. We do not make any representation that we can identify the manufacturer of the EIFS installed on a Property or that it is any one particular manufacturer’s system. We do not attempt to identify the specific type of EIFS on a Property. We are unable to affirm the qualifications or training of the personnel who installed the EIFS cladding. Our inspection is a limited, general visual inspection of the condition of the EIFS cladding.
¹ A qualified person is generally someone who has the skills and knowledge to safely and competently perform the task using appropriate techniques. STO Corporation specifies that EIFS installers be “skilled mechanics who are experienced and knowledgeable in air/moisture barrier and EIFS application, and familiar with the requirements of the specified work.” ParexUSA requires that the “applicator must attend the manufacturer’s educational seminar, must possess a current manufacturer’s certificate of education, and must be experienced and competent in installation of plaster-like materials.” It is typically the responsibility of the builder or contractor to ensure that the installers meet the manufacturer's qualification requirements and that the installation is performed according to the manufacturer's instructions. In the State of Texas, there is seldom any other oversight or enforcement of these qualifications or requirements in residential construction.
² In this usage, “correct” means “conforming to generally-accepted construction industry standards.” IRC Section R703 addresses exterior wall coverings and the water-resistive barrier and flashings required beneath the exterior materials.
³ "Durability of Elastomeric Sealants," Construction Specifier, February 25, 2015.