Hardwood Floors April/May 2017

AT THE SITE

during which the solvents flash or evaporate, the polyfilm can be rolled over the mastic by walking over the film, embedding it in the mastic. Air bubbles that form under the film can be forced out toward the seams with a push broom. Again I recommend using the more durable E1745 membrane. This is a tried and true method still employed by many installers today. 3. Asphalt/Mastic Method— Asphalt roofing felt, or asphalt saturated paper in asphalt mastic applied with a notched trowel at the rate of 50-square-feet per gallon. A second similar coating of mastic and asphalt felt should be added, with overlaps staggered to achieve a more even thickness. Another well-known and tested method still used today. 4. Adhesive Methods — it is extremely important to use the method specified by the adhesive and vapor retarder and/or flooring manufacturer for glue-down methods. Be sure to follow recommended dry times. Always check with the flooring, adhesive, and vapor retarder membrane manufacturer to ensure compatibility before installation. This method is usually warranted by a manufacturer. 5. There are several other manufacturer-specific moisture retarding systems available, including: Subfloor Focus: Minimizing Moisture (Continued) a) Other liquid or semi-viscous materials which typically work in conjunction with or are a part of a specific adhesive system, and even multi- purpose adhesives. b) Two-part epoxy, very moisture resistant. c) Rubberized elastomeric membrane, peel-and- stick method. Quick and easy install. Some of the above may include manufacturer-warranted systems. The manufacturer’s installation details must be read, followed, and strictly adhered to for the warranty to be honored in case of failure. In all cases, installers must verify the acceptability of a particular system with the flooring manufacturer, and also verify adhesive compatibility when planning to glue down over any moisture retarding membrane. If using an adhesive

Screed system over elastomeric peel-n-stick membrane. Photo courtesy of Virginia Hardwood.

method and you are not familiar with the system, check with the adhesive manufacturer, the flooring manufacturer, and the manufacturer of the moisture retarding system before attempting an installation. Proper selection and installation of a vapor retarder material will help you control moisture migration from below the installed flooring. As always, check with your manufacturer for proper use, capability, and installation of the product. Stay tuned for my third and final article in the next edition of Hardwood Floors Magazine where I will cover a few specific examples of vapor retarders as they should be used in different scenarios within NWFA Guidelines. Since it is important for you to be aware of alternate methods, I will focus on a few that may be unfamiliar. Roger Barker is an NWFA Craftsman, Master Craftsman, Advanced Master Craftsman, Vanguard and Ambassador Member and Market Manager Flooring at Fortifiber Building Systems Group in Fernley, Nevada. He can be reached at rbarker@fortifiber.com.

1. 2015 Section R506.2.3, Page 149. 2. 2015 Section 1805.2.1, Page 420. 3. IRC 2015 Definitions, Vapor Retarder Class, Page25 and IBC 2015 Definitions, Vapor Retarder Class, Page 39.

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