Masonry Magazine March 2011 Page. 36
MOISTURE MANAGEMENT
Cavity walls will see a lot of moisture that would pass through a masonry wall.
typically 24 inches on center. One firm manufactures an all-in-one unitized flashing system, where all of the necessary components of an engineered flashing system are pre-assembled in the factory and weeps in the bed joint every six inches.
Weep tubes, cotton rope wicks and open head joints are not preferred as they have been proven to create issues for the building occupants. The three systems have been installed successfully in thousands of buildings. However, the systems noted have a greater ability for insects to enter the cavity. Clogging of the tubes is common, and weep blockage due to disintegration of the cotton rope wicks is often observed.
In cast and cut stone applications, where split tab anchors are utilized, a common trend to use colored polypropylene mesh weeps laid in the bed joint with stone shims on both sides for additional support allows for a discrete method to aid in cavity drainage.
Air barriers, damproofing and building wraps allow for the systems approach in creating an energy-efficient living space for the residence of the building. More designers and contractors agree that the system chosen is based on overall system performance. The importance of proving that the ASTM standards are currently met, manufacturer installation instructions are followed and mil thicknesses are achieved will pay dividends in energy efficiency and customer satisfaction.
Cavity walls will see a lot of moisture more than one might think - that would pass through a masonry wall. As a contractor or designer, it becomes our job to construct cavities that function as intended. The products we use and the methods we follow during construction will reflect the performance of the building and, potentially, our reputation within the building community, IMAS
Steven Fechino is engineering and construction manager with Mortar Net USA, makers of Mortar Net with Insect Barrier, TotalFlash Cavity Wall Drainage System and Blok-Flash CMU Flashing System. For more information, call 800-664-6638, or visit www.mortamet.com.
Special Report
Polyether-Based Sealants and
Adhesives Offer Performance,
Safety and Low VOCS
Polyether-based sealants and adhesives, the advanced formulation polymers that have overtaken urethane and silicone products in Japan and Europe, are now becoming the new standard among some U.S. architects and contractors for use throughout the entire building envelope from foundation to roof.
Since being designated by the Adhesive Sealant Council as a unique product category last year, the use of polyether-based sealants has nearly doubled for both new construction and repair work. The driving forces behind this increased popularity are the superior performance and environmental compliance characteristics of polyether based sealants and adhesives, compared with many urethane-and silicone-type products.
Another important factor: Because these advanced sealants and adhesives contain no solvents, they produce few Volatile Organic Compounds (VOC). This is not only an environmental benefit, but also it makes polyether-based products compliant with increasingly stringent local and state VOC regulations.
VOCs are substances that evaporate into the atmosphere, contributing to climate change, chronic respiratory disorders and cancer. Many sealants that produce VOCs are also flammable, produce imitating odors and tend to degrade over time.
Rewriting the book
Once a polyether-based sealant or adhesive is applied, it reacts with moisture in the air and cross-links to form a tough, long lasting, flexible chain. It cures rapidly, adheres to a wide range of materials, meets the toughest standards for joint movement, won't shrink and won't suntan.
Chem Link Advanced Architectural Products in Schoolcraft, Mich, has developed and popularized the use of polyether compounds throughout the United States, and the developed of a variety of products that address assorted adhesive and sealant requirements throughout the building envelope.
No more shrinkage
Polyether-based adhesives and sealants are cured by water it draws from the air, so there are no solvents to evaporate and cause shrinkage. Because these products cure from the top down and the bottom up, they are watertight and fairly durable within 10-20 minutes, though they typically take two to three weeks to completely cure when, as Graham notes, they become hard as a hockey puck but remain "remarkably flexible.
The power of green
Although the polyether adhesives and sealants were initially popular because of superior performance properties, its no-solvent chemistry has added to sales more recently. In using these products, contractors don't have to worry about confined spaces, flammability or that they will contaminate some other material. IMAS
For more information, visit www.chemlink.com.