ENVELOPE
SYSTEMS/EIFS
Substrates
EIFS, as originally developed in Europe, employ substrates of solid masonry or concrete. Most
application of EIFS in this country is on gypsum-sheathed, metal-stud walls. The concrete or
masonry substrate has the advantages of providing a more stable backup for the finish system than
a stud wall. In addition, gypsum is vulnerable to water damage from leakage or condensation.
Cases of moisture damaged sheathing and corrosion of metal studs have occurred due to water
penetration or accumulation in the wall systems. If the finish were absolutely watertight, then
moisture damage to the substrate would not be an issue. However, it is unrealistic to assume
perfect water-tightness over time in the field. One proposed solution to this problem is not to use
gypsum sheathing at all, and the use of only concrete and masonry substrates is advocated by
some groups. Several other options are described in the article by Piper. If gypsum sheathing is
used, a weather barrier such as 15# felt can be placed between the sheathing and the finish, but
this will require the use of mechanical fastening of the insulation. Alternatively, a weather barrier
can be placed behind the sheathing, but this will protect only the studs and the building interior.
One can also use a more durable sheathing material, such as cement board or cement fiber board.
Crack Control
in order to reduce air and water leakage, it is important to control the cracking of the finish through
proper design and construction. Piper has described the occurrence of several classes of cracks in
EIFS. Diagonal cracks at windows and other large openings can occur if diagonal mesh
reinforcement is not installed at these locations. Such reinforcement is necessary because of the
stresses that are concentrated at these locations. Cracks can also occur at gaps between
insulation boards. This gap becomes partially filled with the base coat, and this T-shaped cross
section in the base coat leads to concentrated stresses that can result in cracks. These gaps can
result from the use of inadequately aged insulation boards, application methods that result in
adhesive being forced between the boards, and excessively out-of-square installations of boards.
Panel joints
The integrity of panel joints is a critical area in EIFS construction. Leaky joints degrade air and
water tightness performance, and can lead to more serious problems with the wall components.
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