Masonry Magazine June 2011 Page. 17
Today, we use the phrase "moisture management in the building envelope" to describe a total-system approach to designing, detailing and specifying products that work together to prevent moisture intrusion and effectively direct any moisture within the wall to the outside. At present, the brick exterior of a cavity wall system is viewed strictly as the veneer of the wall assembly, rather than an actual barrier to moisture.
Considering this, we must look at cavity wall design and construction much differently than we have in the past. The concept of rain-screen design is where the "true" barrier in most wall systems today actually is the outer face of the back-up wall. With this in mind, controlling all types of moisture in the wall assembly takes on an even greater importance.
A major facet of building envelope regarding moisture is the thru-wall flashing system. Today, we are, correctly, viewing flashing as a complete system that includes numerous component options, including drip plates, termination bars, mortar collection devices, pre-formed corners, weeps and vents.
Technology and innovation have brought many new and improved flashing and moisture protection products to market that can withstand high temperatures and ultraviolet exposure. Non-asphaltic adhesives provide distinct advantages over their older rubberized asphalt counterparts, notably, easier installations of the contractor in the field. Copper flashings remain a popular choice among designers, and improvements have been made with clear protective coatings over the copper materials in lieu of asphalt coatings. Newer self-adhesive copper materials are available as well. With the Brick Industry Association stating in its Technical Notes, "It is imperative that flashing be extended at least to the face of the brickwork," UV-resistant membranes are becoming a more popular choice. Still, the masonry industry recommends the use of a drip plate to extend the flashing beyond the outer face of the brick. This is normally accomplished with a stainless-steel drip plate that extending about 38-inch beyond the face and turned down on a 30-degree angle with a hemmed edge.
Aesthetics can be a major problem with these drip plates. So, today, newer drip plates are being manufactured with durable UV-resistant plastics that come in various colors to match a mortar or brick color. As steel-stud wall assemblies continue to become more commonplace, flashings are being adhered onto sheathing www.masonrymagazine.com materials, requiring the use of a termination bar with a sealed top edge that prevents moisture from migrating behind the flashing material.
When discussing thru-wall flashing materials, one of the most important criteria should be the "installability" of the material, with the success of the system largely related to the installation in the field. Certainly, a good, high-quality material is essential. But it can be argued that the ability of the contractor to be able to work with the material
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June 2011
MASONRY 15