What makes EIFS with drainage effective

EIFS with drainage has been available since the 1990s in North America. In southern Ontario, some townships require that EIFS with drainage is used, such as Richmond Hill, Oakville and Burlington. Other areas like Toronto have no such requirements or regulations. As a proprietary system, the drainage capabilities and methods can vary in EIFS depending on the manufacturer, but most EIFS with drainage do share some similarities. All have some kind of drainage cavity for water to leave the system, and all require a weather-resistive barrier between the drainage cavity and the substrate to prevent water that gets behind the EIFS from infiltrating the supporting wall. This weather-resistive barrier, or WRB, can come in sheet form or be liquid-applied. The cavity, on the other hand, can be created using a multitude of methods. For example, it could be a space cut into the foam to allow for water to run through, or be ‘ribbons’ created by thicker beads of adhesive where the foam meets the substrate. These ribbons result in spaces that act as a drainage cavity in the EIFS.

The drainage capability of each system depends on the method and materials used.

Determining drainage capability

The American Society for Testing and Materials has tested EIFS in the past, using a test wall with EIFS with a drainage cavity and without variables like windows. The wall is realistic in every way possible and incorporates some method for which the water can leave the wall, either small holes in the bottom, or by implementing flashings. Whatever the method used, it should be aesthetically pleasing and suited for use on homes or commercial properties. This testing goes further to add water to the wall and then determine the drying time and the effectiveness of the drainage system as well as how much water is retained overall within the sample wall. Different drainage systems yield different results, and some are slow to drain while other systems may dry faster than others. This testing method is difficult to apply to real life situations and is not really suited to being used on in-place walls, which as mentioned, may incorporate a mix of different drainage elements into their construction. The testing can however, provide ideas on how to improve drainage and eventually provide some kind of regulatory standard for EIFS with drainage.

Creating adequate drainage in EIFS

Without a standard measure of drainage to work from, it’s imperative that when installing EIFS with drainage, the wall drains as effectively as possible.

Variables such as climate also need to be taken into consideration. Hotter, dry climates would rarely if ever require adequate drainage in their EIFS. If it were to rain, it’s more than likely the wall would dry quite quickly and retain no water, but areas prone to inclement weather such as strong winds and heavy rain would need more than adequate drainage, especially since the water would not be as quick to leave the wall.

The basic principles of creating EIFS with decent drainage are as follows:

  • Grooves carved directly into the insulating expanded polystyrene foam drain water quite well, as do ribbons of adhesive between the foam and substrate that are installed vertically. However, ribbons created horizontally do not drain effectively.
  • The larger the drainage cavity, obviously the better the drainage will be. However, there is a fine line to tread between creating cavities large enough to drain all of the water and so large that they negate the insulating properties of the EIFS wall by allowing too much air to pass through behind it.

What about barrier or face-sealed EIFS?

One could allow barrier, or face-sealed EIFS, to drain by using a weather-resistive barrier as well as using fasteners to attach the foam insulation board directly to the substrate. This will allow for drainage, but not in adequate time, nor very efficiently. Water may also be retained in between the substrate and foam that has no way to escape or dry at all, leading to mould and rot problems in the future.

Not using any drainage at all

Neglecting to leave room for any drainage capabilities within an EIFS wall is not necessarily a bad thing and sometimes incorporating a drainage cavity with an EIFS wall can lead to more problems than it solves. If the wall is adequately back or edge wrapped, proper care is taken with detailing such as flashing and joints and there is no possibility of water getting into the system in the first place, having EIFS with drainage is unnecessary. A quality EIFS wall is what makes the wall effectively water-resistant, not finding a way to get the water out later once it’s already infiltrated the system.

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