Current Acrylic
Stucco Issues

Keep Dry as a Mallard The main factor contributing to the problems encountered with the acrylic stucco when applied on top of the insulation known as Externally Insulating Finishing System (EIFS), is the inability of the assembly to dry through the “EIFS making the performance of the system somewhat climate dependent. In a document prepared by the National Research of Canada (NRC) in September 2000 a number of deficiencies have been identified, the most important one being failure of the system to drain and dry when water enters through the exterior causing softening of the drywall, delaminating of drywall sheathing, expansion and warping of OSB or plywood sheathing, corrosion of metal fasteners were some of the concerns raised by NRC in the above mentioned publication.

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Korax Technologies Solves the EIFS Rain Screen Problem

Over the last number of years stucco finishes, both cementitious and acrylic, are under scrutiny and have been the topic of many technical and non-technical discussions. The thickness of cementitious stucco has been an issue in Alberta over the last 5-10 years and acrylic stucco has been the main topic of discussion among designers, building owners and building officials.

The issue with “leaky condos” in British Columbia has been the topic of many newscasts and it has affected many individuals. Many papers have been written on the topic most of them by the proponents of the system (especially the acrylic stucco), which provided little or no explanation as to why so many buildings experience so many problems. The problems experienced by these systems are blamed on applicators, contractors, designers, etc.

This site deals with the issues and factors affecting the performance of these systems and introduces the principles of a vented rain screen to stucco finishes. The principles of rain screen wall assemblies have been known to designers and building officials for many years and because of the problems encountered with other wall assemblies it is now the preferred system, and one recommended by designers and building officials.

The Problem

Typically, EIFS is applied on sheathing as a face-sealed, soft coat finish and when it works all incident rain-water is prevented from penetrating into the wall assemblage. However, when there are imperfections or defects in the EIFS water is able to penetrate the surface and, since traditional EIFS systems possess little ability for storing the moisture, the relative humidity quickly reaches saturation which can then penetrate into the wall system causing damage. In any case, defects eventually develop at door and window openings, leading to trapped moisture, deformation of the main structural elements deflection of beams, and thermal moments.

Others Have Tried

Attempts have been made at developing a rain screen panel for EIFS systems but they were not able to provide baffles that separated regions of different time-averaged exterior pressures from each other nor could they create a cavity that could react to rapid changes in exterior pressures. Furthermore, they possess the following disadvantages:

The air-barrier was trowelled on making it subject to thickness variations and requires the use of emulsified polymers that do not withstand long-term exposure to moisture.
The ventilation channels are too small for adequate drying and moisture can still enter through gravity flow and cross channels prevents ventilation. Furthermore, ventilation at the location of the air-vapour barrier as recommended by some of the existing system is totally inappropriate and ineffective.

Korax Technologies Succeeds

The RainScreen Panel™ effectively overcomes all of these limitations making it the true rainscreen panel for EIFS and conventional stucco applications.

Other Applications

The RainScreen Panel™ is not limited to EIFS and conventional stucco. The design allows for a great deal of versatility in its use. Whether it’s rubble masonry veneer, stucco on wood frame, as subgrade drainage, the panel gets the job done.

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