The Home Building Industry's Technical Information Resource

Back to Standard View
Search TechnologiesAbout Technology Inventory
Browse by Building System

Symbol Legend
Adobe Acrobat Reader required for PDF documents

PDF documents require the free Adobe Reader.

All PDF documents open in a new browser window. Close the browser window to return to the site.

Exterior Insulation and Finish Systems (EIFS) - Drainable Systems

A synthetic stucco cladding system that acts as a rain screen barrier

Cross-section of EIFS layers.

Exterior Insulation and Finish Systems (EIFS), also called synthetic stucco, are available in drainable or barrier systems that resemble traditional masonry stucco finishes. EIF systems are aesthetically attractive to many people due to the variety of colors and textures available, and special architectural features that are easily created. While among the more expensive finishing systems available, drainable EIFS, if properly applied, may benefit the homeowner by providing an insulating exterior finish without the worries about water damage associated with barrier EIFS.

Drainable systems may prevent water accumulation problems that sometimes occur with barrier or face-sealed EIF systems. A barrier EIFS resists water penetration at its outer surface but does not allow water that gets behind the exterior surface to drain out of the wall system.

Drainable EIF systems consist of an extruded (XPS) or expanded polystyrene (EPS) or a polyisocyanurate foam glass fiberboard. An installer applies them with special mechanical fasteners or adhesives to a metal, plastic, or glass fiber mesh, creating a drainage plane. Alternatively, a grooved foam board can allow drainage. The mesh covers a weather-resistive barrier such as building paper or housewrap, which in turn covers the sheathing or substrate. OSB, plywood, and exterior-grade gypsum sheathing are the most common substrates. A base coat of a cement/polymer mixture covers the insulation board and provides a base for embedding a fiberglass mesh. A flexible, acrylic-modified finish coat in the desired color and texture is applied over the base coat.

Application of a special sealant and flashing are also required to provide water-tight seals and to divert water from critical junctions between EIFS and building components.

Energy Efficiency

These systems also improve insulation performance, reducing the heating and cooling loads on the home and improving efficiency.

Quality and Durability

EIFS drainable systems help keep moisture from damaging the homes sheathing and insulation, making the home last longer and remain comfortable.

Kind of difficult

Most EIFS manufacturers now market drainable EIFS. EIFS System components are typically available to trained contractors through specialty distributors. Water accumulation problems that occur with barrier EIFS can also occur with drainable systems if design or installation is not correct. Water intrusion, impact damage, cracking, adhesion failure, finish delamination, and staining from dirt, mold, or mildew can occur. Cold temperatures and wet conditions usually hamper installation and special protection during construction may be necessary to protect uncured materials.

Some builders’ insurers will not insure houses with drainable and/or barrier EIFS due to the problems with barrier systems. This may change, as drainable systems become more accepted and less prone to water intrusion.

EIFS are among the more expensive exterior finishes. Because drainable systems for residential application are relatively new, a limited number of trained and experienced installers are available. The EIFS product manufacturer should be contacted for a listing of trained installer contractors.

Both types of EIFS are high-end products, with installed prices often similar to those of brick veneer. Drainable EIFS can cost between $4.50 and $7.50 per square foot, roughly $1.00 or more per square foot than barrier systems. In comparison, the installed cost of vinyl siding is about $1.50 to $4.00 per square foot.

Not Applicable

Some building codes restrict the use of barrier EIFS. Some areas allow only drainable systems and require third-party inspections during construction phases of the EIFS system.

Not Applicable

Only manufacturer-trained installers using materials made or approved by a single manufacturer should install EIFS. Proper design and careful selection and installation of materials such as weather resistive barriers, flashing and sealants are critical in order to avoid water intrusion problems and to maintain manufacturer warranties. The building owner, architect, builder, or third-party inspector should be fully aware of all special requirements and conditions, including those of the manufacturer and EIFS Industry Manufacturers Association (EIMA), to ensure that requirements are followed without exception. A Quality Control Plan for the Installation of EIFS that outlines project responsibilities and provides inspection and installation checklists is available from the NAHB Research Center.

Not Applicable

EIF systems, either drainable or barrier, have become popular because the continuous insulation board improves energy efficiency. Also, the insulation board allows easy construction of architectural details like quoins at corners. Finishes are versatile, available in various textures and colors and are less prone to surface cracking than traditional stucco. Homeowners can also re-color EIFS at any time, which is not possible with some exterior claddings such as vinyl siding.

Disclaimer: The information on the system, product or material presented herein is provided for informational purposes only. The technical descriptions, details, requirements, and limitations expressed do not constitute an endorsement, approval, or acceptance of the subject matter by the NAHB Research Center. There are no warranties, either expressed or implied, regarding the accuracy or completeness of this information. Full reproduction, without modification, is permissible.