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Technical Review Introduction
by James B. (Jim) Posey
The typical EIFS installation is face-sealed, soft-coat (Type PB),
adhesive applied on sheathing or, less commonly, masonry, with
single stage joints. When it works, all incident rainwater is
excluded at the visible exterior surface, despite exposure to
extremes of temperature, ultraviolet degradation, and other causes
of damage. However, it does not always work. When it is raining,
once there is a film of water on the surface, it is pushed into
any defects by wind pressure. Water that enters the system must
exit by gravity to the interior or, if trapped, evaporate through
the layers of the wall to interior or exterior as conditions
permit. The system has very little capacity for storage of adsorbed
or capillary moisture, either on the surface, or within the EIFS
materials. A more porous material would delay formation of a
film of water on the exterior surface, and thereby reduce penetration
into the wall. In addition, with EIFS less water is needed inside
the system to raise the relative humidity to saturation. So,
defects in the exterior surface are likely to cause wetness within
the wall and damage to moisture sensitive substrata.
In many cases, face-sealed systems are capable of good performance.
Dry climate, sheltered locations, protection by overhangs, and
solid masonry or concrete substrate walls that can store moisture
without damage are all positive factors. In a 1993 field survey
of Canadian EIFS installations, 50% of installations examined
were serviceable, without serious defects.1 On the other hand,
30% were in need of extensive repair or replacement. The oldest
installation examined was 13 years old at the time. It was in
good condition then, and appears to remain so today, except that
the finish coat has now eroded to reveal the base coat in some
locations. Another installation, also in good condition, was
serving as a sloped roof! Many of the problems seen in the less
successful installations could have been avoided without design
changes. But, if the designs had not relied on a perfect seal
at the exterior surface more installations would have been in
serviceable condition, despite less than perfect installation
or subsequent deterioration.
References
1 Williams, Mark F. & Lampo, Richard G.,“Development,
Use, and Performance of Exterior Insulation and Finish Systems
(EIFS)”, ASTM STP 1187, Philadelphia, 1995.
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