Water resistive barriers and drainage EIFS

Often building codes may specify that for whatever reason, drainage Exterior Insulation Finishing Systems must be used, especially is the substrate is vulnerable to moisture. This will often necessitate a protective coating between the EIFS drainage components and the substrate, called a water resistive barrier coating. The lamina of EIFS is already applied in a manner that allows water to run off of the exterior and does not require preexisting drainage capabilities, and therefore does not require WRBs, but when drainage components are implemented, WRBs should be incorporated and may be demanded by building codes in the area.

By design, EIFS with drainage have grooves, cavities or gaps where they meet the substrate to ensure water can be drained out effectively. Somewhere, between these gaps and the substrate, a WRB will be placed. WRBs come in many forms, including liquid-applied coatings, papers and films.

Water resistive barrier characteristics, qualities and necessities

Water resistive barriers do not have to withstand the same elemental force that EIFS lamina might, either from the sun, wind or rain. However, one can imagine leaving WRBs exposed in the dead cold of a Toronto winter or the blazing hot sun of an Ontario summer and as such they must be able to defend themselves somewhat adequately, as we’ve all passed still-under-construction buildings wrapped in paper or other WRBs that is left exposed for a good period of time before the final wall cladding is applied to the building.

WRBs must not be easily penetrated by water, even though rain will not be driving water into the WRB as it will the EIFS, and instead the water will trickle down the WRB in behind the EIFS. The WRB must adhere to the surrounding EIFS and substrate effectively to provide adequate water-resistance. Water vapour may also be able to permeate the liquid-applied WRBs, so care must be taken to ensure that not too much moisture will get in, and that it will be able to escape later.

WRBs may also be manufactured by EIFS producers, but can be available and sourced from different suppliers. EIFS-specified WRBs should be used in these instances, as they have been designed to be used along with the EIFS system in question and the installer will likely get much more support from the manufacturer of the overall system if needed, as opposed to the producer of just one component.

Liquid-applied WRBs, similar to EIFS, are a part of a total system that incorporates elements such as joints, openings and flashings. All of these elements and components must be considered for an effective water resistive barrier.

Liquid-applied water resistive barriers vs. paper and film

The liquid-applied WRBs, as they are in one piece, are more vulnerable to cracking than the paper or film applications but can offer other advantages over other forms of WRBs, such as the use of substrates that do not require fasteners or cannot support them as well as direct adhesion to the EIFS itself. Reinforced joints between sheathings are necessary to proper installing of WRBs, as obviously if the WRB cracks due to any sort of wall shifting its important ability to repel water will be compromised, and the joints must be adequately reinforced to prevent this cracking.

Film and paper WRBs have joints and areas where they overlap, where moisture can become a problem if they’re not sealed properly. Liquid-applied WRBs do not have these issues as they are one, continuous application.

One drawback to the liquid-applied WRBs is that they cannot bridge joints like a paper application could, but this issue can be solved by incorporating paper, tape or flashings to adhere the WRB to so that it can successfully keep water out.

Liquid-applied WRBs are constantly being reviewed, tested and re-designed to ensure they will meet various standards and building codes. In the future the industry may be able to expect WRBs that can adapt to certain situations, be semi-permeable and dry faster.

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