Restoration Guide: EIFS and Stucco for Exterior Walls
Editor's Note: This is article 15 of 18 in Chapter 2:Exterior Walls of the Old House Web Restoration Guide. This guide was developed and edited for old homes from original materials in the U.S. Housing and Urban Development (HUD) Rehab Guide.
15. EIFS AND STUCCO
Exterior insulation and finishing systems (EIFS) were first introduced in the United States in the 1970s and have since largely replaced traditional three-coat stucco systems. However, EIFS's market share still remains relatively small--about 3.5 percent of the residential wall siding market, according to the the EIFS Industry Members Association.
EIFS has many benefits, including additional insulation outside a home, reduced air infiltration, and flexibility in choice of design. Thousands of residential and commercial buildings clad in EIFS have experienced no problems over time, but there have been class-action lawsuits filed against major manufacturers due to problems associated with moisture penetrating the finishing system. Use of EIFS has been abandoned in certain states, particularly those with severe swings in temperature and high levels of moisture.
1.1: New Developments in EIFS
To alleviate public concern regarding the use of EIFS, insurers, building industry officials, and manufacturers developed new EIFS products that incorporate drainageways and moisture barriers behind the insulating panels to give any water that penetrates the system an escape route. Many of the problems associated with this type of wall finishing system were caused by moisture buildup that led to rot, fungus, and deterioration of structural sheathing and wall studs/plates.
Section 2--Repairing Damaged EIFS
During a home renovation, any house that has an older EIFS system should be examined carefully for signs of water damage. Fixing deteriorated sections of EIFS during a remodeling job is easy if the exterior sheathing behind the finishing system is intact. The damaged area should be cut out and a new section installed following manufacturer's installation guidelines, since EIFS installation varies from different manufacturers.
When remodeling a home with EIFS, any underlying causes that led to water damage must be corrected to avoid further deterioration. Deficient flashing and caulking should be replaced. There are a number of sealant systems on the market specifically designed for remediation work.
If large sections of the barrier system are damaged, the entire wall panel should be stripped to exterior sheathing during the home renovation. Sometimes it will be necessary to remove sheathing, windows, trim, and other materials to fully rehab the damaged area. Repairs of EIFS work best on small sections of damaged wall.
Section 3--Installing New EIFS
EIFS are made from three layers:
- An inner layer of foam insulation board that's secured to the exterior wall surface
- A water-resistant middle layer consisting of a polymer and cement base coat that's applied over the insulation and reinforced with a glass fiber mesh
- An acrylic exterior textured finish coat
Use of exterior insulated and finishing systems should be carefully examined before being chosen as the siding material. Many residential contractors don't have the same amount of experience installing this type of wall finishing system as some commercial contractors. Some states do not allow use of EIFS over wood frame construction due to past problems with moisture, and warranty specifications also vary by manufacturer.
Moisture drainage systems are becoming much more prevalent with building professionals. They are similar to EIFS except that they employ a drainage system behind the wall with either vertical grooves in the insulation board, vertical furring strips, or a woven fabric drain mat. Flashing, sealants, and other weather barriers are just as crucial in this system, however.
New EIFS barrier systems should end well above graded dirt to prevent infestation by termites and carpenter ants and also allow for inspection of the system over time.
EIFS requires careful installation and systematic monitoring to ensure structural integrity, and there is still debate from various building industry organizations about the effectiveness and performance of EIFS and moisture drainage systems.
Portland cement stucco has a long history in the U.S. Three-coat stucco systems consist of a scratch coat, a brown coat, and a final color coat, although two-coat systems often are used over masonry.
4.1: Fixing Damaged Stucco
Mending hairline fractures in a stucco wall usually makes the patch much more noticeable than the original defect. Cracks 1/8" to 1/4" can be fixed by scraping out the color and brown coats and filling the gap with an acrylic bonding agent.
Larger cracks and holes can be fixed with a stucco patch, and a self-adhesive fiberglass mesh can be added for strength.
There are many elastomeric coatings sold that can reseal and recolor old stucco.
4.2: Installing a New Stucco Exterior
In Northeastern and North Central states, stucco most often is installed over gypsum sheathing with diamond-shaped lath that keeps plaster off the sheathing. This type of lath also creates drainage for moisture. Stucco is usually applied directly to masonry without a lath. In the South and Southwest, stucco typically is installed over paper-backed lath without sheathing--but walls must be braced or the stucco can crack.
Stucco provides exceptional durability in a variety of climates. It's a good choice for any home restoration--providing it matches local architectural styles. The top coat of stucco can be colored, or colored coatings can be applied.