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Building Envelope Design Guide - Exterior Insulation and Finish System (EIFS)

by Gary L. Zwayer, RA
Wiss, Janney, Elstner Associates, Inc.

Last updated: 06-04-2010

Introduction

Exterior Insulation and Finish System (EIFS) is an exterior wall cladding that utilizes rigid insulation boards on the exterior of the wall sheathing with a plaster appearance exterior skin. EIFS in its current basic form was developed in West Germany in the 1960s and introduced in the United States in 1969 by Dryvit. The Dryvit system consisted of expanded polystyrene (bead board) attached adhesively to the sheathing and covered with a lamina composed of a modified cement base coat with woven glass fiber reinforcement and a textured colored finish coat. Over the years, variations of this system have been developed.

 

Description

The most common type of EIFS is the polymer based (PB) system. This system has a nominally 1/16 inch thick reinforced base coat applied to the insulation prior to application of the finish coat. The insulation typically consists of closed expanded polystyrene (EPS) and can be either adhesively or mechanically attached to the sheathing. The second and less common type of EIFS is the polymer modified (PM) system. This system has a nominally 3/16 inch to 1/2 inch thick reinforced base coat applied to the insulation prior to application of the finish coat. The insulation typically consists of extruded expanded polystyrene (XPS) and is mechanically attached to the sheathing and or wall structure.

EIFS is available in two basic types: a barrier wall system or a wall drainage system. Barrier EIFS wall systems rely primarily on the base coat portion of the exterior skin to resist water penetration. Therefore, all other components of the exterior wall must either be barrier type systems or be properly sealed and flashed to prevent water from migrating behind the EIFS and into the underlying walls or interiors. Wall drainage EIFS systems are similar to cavity walls; they are installed over a weather barrier behind the insulation that acts as a secondary drainage plane. The weather barrier must be properly flashed and coordinated with all other portions of the exterior wall to prevent water from migrating into the underlying walls or interiors.

Fundamentals

All EIFS are proprietary systems and the components of the system should not be modified beyond the limits stated in the manufacturer's literature. The design of the interface with other components of the wall system is the responsibility of the wall designer. Details should make clear the design of the final construction. If necessary, the sequence by which the wall assembly is to be constructed is addressed in the details. In general, construction conditions of the EIFS that should be detailed if they exist on the building include terminations, openings, joints, objects mounted onto the surface and special treatments to the surface.

Performance Issues

Thermal Performance

The popularity of EIFS comes from its insulating qualities to reduce thermal loads on the exterior building wall and the light weight, low cost, and the ability of the system to be sculpted into shapes and patterns to achieve different aesthetic effects. The thermal performance of the exterior insulation is based on the thickness of the insulation selected. The insulation should never be installed or modified to less than 3/4 inch in thickness.

Moisture Protection

Problems observed with in-service EIFS installations are primarily related to moisture intrusion. EIFS provides protection against moisture infiltration at the base coat; however, moisture migration through openings for windows, flashings and other items, or holes and cracks in the EIFS itself, have allowed leakage to occur on EIFS clad buildings. With barrier EIFS installations, or where weather barriers and flashing are improperly installed in conjunction with wall drainage EIFS installations, moisture has entered the wall system at these locations and caused damage to the wall sheathing and framing. The extent of these occurrences on wood frame structures has led to class action lawsuits.

Fire Safety

Consult the EIFS Industry Members Association (EIMA) for additional information on this topic.

Acoustics

Consult the EIFS Industry Members Association (EIMA) for additional information on this topic.

Material/Finish Durability

EIFS finish coats come in a wide variety of colors and textures similar to those of stucco. Since the base coats are relatively thin, especially in PB systems, they are susceptible to impact damage. Color retention is relatively good.

Common Problems for EIFS are as follows:

  • Failure to install or properly install sealant joints around windows, doors, pipes, conduits, and other penetrations of the field of the EIFS.
  • Failure to flash window and door openings in the field of the EIFS to divert leakage through the window or door to the exterior.
  • Failure to install diverters (kick-out flashing) at ends of roof flashing terminating in the EIFS wall.
  • Failure to properly backwrap edges of EIFS at terminations and penetrations in the field of the EIFS.
  • Failure to install expansion joints at floor lines in EIFS applied over wood frame construction.
  • Failure to notch insulation boards at corners of openings for windows and doors to avoid insulation board joint at the corner of the opening.
  • Failure to install diagonal mesh in lamina at corners of openings for windows and doors.
  • Failure to terminate EIFS above grade, especially in termite prone regions.
  • Installation of decks over EIFS without proper flashing.
  • Unrepaired impact damage.
  • Inadequate base coat applications at corners.
  • Inadequate base and finish coat application in reveals.
  • Installation of reveals at board joints.
  • Lack of adequate slope on skyward facing surfaces.
  • Damage from ropes, cables, etc. to EIFS parapet tops.

Maintainability

Maintenance of the EIFS lamina and sealants at penetrations or terminations is critical to the performance of the water resistive characteristics of the EIFS. Holes and cracks should be repaired as soon as possible. Repair methods for holes and cracks in EIFS are simple and the manufacturers publish recommended methods. Maintenance of joints sealants is the same as that for other types of wall claddings, except that care must be taken to prevent damaging the EIFS when existing sealants are removed.

Applications

See Appendices for climate-specific guidance regarding building enclosure design.

Details

Please see the details section and consult the manufacturers web pages referenced in this section for additional information regarding this topic. Due, in part, to issues and concerns related to the integration of EIFS with surrounding wall systems and wall penetrations in both residential and multi-family, commercial-scale construction, the EIFS industry and its members have developed a series of informative and well-developed, three-dimensional details for façade interfaces and related conditions that are useful starting points for detailing EIFS.

DWG iconDWF iconPDF icon

The following details can be downloaded in DWG format or viewed online in DWF™ (Design Web Format™) or Adobe Acrobat PDF by clicking on the appropriate format to the right of the drawing title. Download Autodesk® DWF Viewer. Download Adobe Reader.

Drained EIFS Roof Interface Kickout Flashing  DWG | DWF | PDF

Drained EIFS Window Head and Jamb  DWG | DWF | PDF

Drained EIFS Window Sill and Jamb  DWG | DWF | PDF

Emerging Issues

Emerging issues in the EIFS industry include:

  • Drained EIFS
  • Improved Interface Detailing for Exterior Wall Penetrations
  • Developing Field Test Standards for Water Penetration Resistance (ASTM)

Relevant Codes and Standards

There are virtually no limitations on the locations where EIFS can be used as an exterior wall cladding beyond those imposed by codes. These occurrences of water infiltration have also led to many code restrictions on the use of EIFS. These code restrictions are evolving and changing as further testing is developed and implemented. Most codes require a code evaluation report for the selected manufacturer's system and may impose additional restrictions on the use of barrier EIFS. Applicable local codes should be consulted prior to designing EIFS claddings.

Codes also restrict the maximum thickness of the insulation, particularly with regard to fire protection. Most codes limit thickness to 4 inches maximum or require a study of the average fuel contribution of the insulation.

Additional Resources

WBDG

Design Objectives

Functional / Operational—Ensure Appropriate Product/Systems Integration

Products and Systems

Section 07 92 00: Joint Sealants, See appropriate sections under applicable guide specifications: Unified Facility Guide Specifications (UFGS), VA Guide Specifications (UFGS), DRAFT Federal Guide for Green Construction Specifications, MasterSpec®

Major resources for information regarding EIFS and its proper use are manufacturer's catalogs containing product description and standards, specifications, details, and installation instructions; the Exterior Insulation Members Association (EIMA); and ASTM International.

Publications

  • CMHC Best Practice Guide—EIFS

Organizations/Manufacturers