Over the past several years, a sixmember consortium comprised of EIFS manufacturers – Durabond, Sto Corp., Dryvit Systems Canada, BASF Wall Systems, DuRock Alfacing International Ltd., and Adex/Akrilon – conducted a research program in consultation with the Canadian Construction Materials Centre (CCMC) to evaluate performance of EIFS with liquid applied barriers (LABs) over wood-based sheathing.

As a result, performance criteria was established for this application. All of these manufacturers have submitted their LAB products for evaluation to CCMC and subsequently have had them recognized for use over wood-based sheathing.

Although CCMC does not have regulatory jurisdiction, its evaluations are referenced by municipalities, resulting in wider recognition for the products’ potential use. As a result of the research, opportunities have opened for EIFS manufacturers that use them in conjunction with their systems over wood-based sheathing. The testing requirements for LABs are much higher than for other barriers, meaning the products have to perform far better overall. John Edgar, technical manager for Sto. Corp. says the drainage test criteria for EIFS requires that the products be 99 percent efficient. “EIFS meets the standard,” says Edgar. “I doubt there is another cladding that can.”

There are few building materials that can provide the water-tightness and air-tightness properties of LABs, which are seamless and essentially tearproof upon installation. LABs are able to resist hydrostatic pressure for days, compared with building papers and other barriers that only last minutes, according to one manufacturer-led study, and the products are priced competitively to leading building papers.

Sto. Corp. manufactures Sto Guard and Sto Emerald Coat LABs. StoGuard is a system of products that, combined, act as a sprayon waterproof air barrier that can be used under brick, wood, vinyl, cement siding, Portland cement stucco, and EIFS. Sto Emerald Coat is a spray-applied or rolledon product most suitable for use under Portland cement stucco, siding, and stone.

According to the company’s website, the use of an effective air barrier can reduce the risk of moisture condensation in the wall assembly, increase the thermal efficiency of the wall, provide energy cost savings, and increase occupant comfort. A study of commercial buildings by the National Institute of Standards and Technology (NIST) confirmed that air barriers promote energy savings ranging from 30-40 percent for heating climates, and 10-15 percent for cooling climates.

DuRock Alfacing’s product, Polar Bear, tailored to low-rise residential applications, was the first to pass CCMC criteria. It is formulated with a 100 percent acrylic emulsion and is trowel-applied. Polar Bear contains fibers that enhance the cohesive and tensile strength for added durability, and can also be used as an insulation adhesive.

The low water absorption combined with a high flexural strength makes Polar Bear an ideal water penetration barrier for use on exterior wall systems; in particular, 1/2-inch-thick plywood and a minimum 7/16-inch-thick OSB. As part of an air barrier system for a wall assembly, Polar Bear is compatible with most transition membranes comprised of bituminous SBS with fabric or cross-laminated polyethylene backing, as well as bituminous mastics and polyurethane foam sealants.

Andre Turrin, technical director for DuRock, says though it’s only been three years since the evaluation, there’s definitely been an increase in the usage of LABs over wood because of reliance on CCMC approval by municipalities.

“It’s still hit or miss, where one municipality requires it and another doesn’t,” says Turrin. “But the more municipalities endorse these evaluations, the more likely others will follow suit.”

Bill Egan, engineering and development manager for BASF Wall Systems based in Jacksonville, Florida says the CCMC approval of LABs over wood has a far reach in Canada, especially in the east and in homes, which previously generally used a layer of gypsum sheathing over the wood-based sheathing, increasing the total installed costs.

“[The evaluation] is exactly what officials are looking for to validate the use of these products,” says Egan.

There are a number of advantages to LABs. “As an example, traditional building paper as it exists is not an air barrier,” says Egan.

“And window openings have to be weatherproofed, which is a lot easier with LABs because of weatherproofing accessories like fabrics and peel-and-stick membranes.”

BASF Wall Systems offers two LABs for the Canadian market: Senershield, a trowelapplied polymer based material mixed one-to-one with Portland cement, and Senershield R, which is typically rollerapplied. Senershield is suitable for EIFS applications over exterior gypsum sheathing board, cement board, or unit masonry, while Senershield R is typically roller-applied over common EIFS substrate materials including exterior gypsum sheathing, cement board, OSB, and plywood.

Turrin agrees that LABs probably won’t replace other systems entirely, but says that because they adhere directly to the sheathing and form a composite material, they are in a class of their own as waterresistive air barriers. “They are definitely the way to go,” he says. “I can forsee the day when LABs are used behind other claddings as well.”

The CCMC evaluation has definitely helped Adex/Akrilon in closing the credibility gap when promoting residential EIFS, says president and CEO, Rafaël Bao.

“With regards to our international sales, notably in the UK, the validation provided by the successful CCMC evaluation over wood substrate has helped us in promoting EIFS as a proven and economical alternative cladding system for residential construction,” he says.

The company’s participation in the consortium led Adex/Akrilon on developing a whole new generation of membranes, including the Hydroflex-WO trowelapplied LAB and the Hydroflex-TAC – a unique “dual-function” product that acts as an LAB and adhesive used in conjunction with the Adex EPS-GD (grooved insulation board).

Dryvit Systems Canada markets a variety of LABs, allowing for the tailoring of wall assemblies to meet particular project design needs, says Peter Culyer, manager, marketing and technical services.

“The participation of CCMC in the evaluation of LABs and EIFS in general has been a very important component in the establishing of EIFS in the Canadian market place as a cladding capable of meeting required code intents.”

Dryvit’s Backstop NT is a flexible, noncementious water-resistive membrane intended for use with Dryvit EIFS. It is approved for use over core treated exterior grade gypsum sheathing, Georgia-Pacific’s DenGlass Gold®, exterior cement and calcium silicate sheathing, APA exterior grade CD-X plywood, exposure 1 rated PS2 durability OSB, and unpainted CMU or concrete.

“Backstop NT has shown to provide a level of protection that papers and other sheet applied materials have not demonstrated and we foresee the emergence of LABs in construction practices beyond EIFS,” says Culyer.

“To that end Dryvit will be positioning its LABs for use behind alternative claddings in the very near future. LABs are simply better performing and easily installed, faster than sheet applied barriers.”

John Garbin, president of the EIFS Council of Canada and the EIFS Quality Assurance Program Inc., says the addition of LABs by the EIFS industry manufacturers further enhances the EIFS value proposition as a preferred cladding of choice among designers and users.

“The fact that an EIFS system does provide excellent and compatible multipurpose LABs to its long list of building science benefits places EIFS in an enviable position especially when actual on-the-wall performance and single source availability are taken into consideration,” he says, adding that the design community has come to expect from the EIFS industry the development of material solutions that better overall building enevelope design.

“We are also proud of the fact that the EIFS industry is making its LABs available to use with other cladding options as it underscores the industry’s leadership position,” says Garbin. CWCJ