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Peel and stick flashing tape or membrane: this article describes the selection and installation of peel-and-stick flashing membranes used on building exteriors to seal housewrap joints and to seal against air or water leaks around windows, doors, or other openings. Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman. Using Building Flashing Membranes - Peel & Stick Flashing TapeThis article series discusses best practices construction details for building exteriors, including water and air barriers, building flashing products & installation, wood siding material choices & installation, vinyl siding, stucco exteriors, building trim, exterior caulks and sealants, exterior building adhesives, and choices and application of exterior finishes on buildings: paints, stains. This article series includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons. Details for Installing Peel and Stick Flashing TapeWe like to install flashing tape in the same sequence or overlap pattern as if it were metal flashing - that is, the upper horizontal flashing tape overlaps the vertical tape installed (first) at the sides of the window. To assure that we respect that water runs downhill, we install housewrap, window and then peel and stick flashing tape around a window in this order:
This flashing tape is very sticky on one side (peel off the waxed paper as we show). The other side of this product is covered with aluminum foil to improve its performance. This sticky flashing membrane tape will also seal nails that may penetrate its surface after installation. Also see FLASHING WALL DETAILS and FLASHING ROOF WALL DETAILS. If you are building a deck see Deck Flashing at Building. Adapted/paraphrased with permission from Best Practices Guide to Residential Construction. Steven Bliss. Peel-and-stick eaves membranes have been used for nearly 20 years to prevent roof leaks from ice dams and other roofing trouble spots. These are typically available in 36-inch widths and are used to protect eaves, shallow-pitch roofs, and other problem roof areas. Over the past few years, a new family of related products has been introduced to help seal walls against water intrusion. Peel-and-Stick Flashing Tapes, Types, Uses, Applications
The foil faced products may be left exposed to the weather permanently, whereas the plastic-faced tapes should not be exposed to sunlight and weather for more than 30 days (longer for some brands) since UV radiation will degrade the facing. Comparing Modified Bitumen vs Butyl Peel and Stick Flashing TapesMost flashing membranes are made from modified bitumen, the same rubberized asphalt used in eaves flashing. Some use a more expensive butyl rubber core, which stays more flexible in cold weather and is more stable at high temperatures. Butyl products also bond better to difficult substrates than modified bitumen and can be peeled off and adjusted during installation. Moldable Flashing - Butyl-basedA unique butyl-based flashing tape from DuPont, called Tyvek FlexWrap®, has a wrinkled facing that allows it to be molded easily to irregular shapes such as the head flashing of round-top windows. It can also be bent to create a pan flashing at window sills without any cutting and folding at the corners. Despite the higher material costs, labor savings make this product appealing for tricky applications. Applications for Flashing TapesThese products offer several distinct advantages over metal flashings: They are easily bent or molded for an accurate fit, can accommodate settlement and shrinkage movement, are self-sealing around nail holes, and bond well to a variety of materials, including metal, wood, plywood, and vinyl window flanges. Flashing tapes provide long-lasting waterproof protection if installed correctly. Oriented-strand board (OSB), concrete, and other masonry materials, however, can be problematic for some of the rubberized-asphalt flashings and may require priming for a good bond. Consult with the product’s specifications for compatible surfaces and priming requirements. Guide to the Installation of Flashing MembranesTo obtain the best results with these products and be protected by the manufacturer’s warranty, it is advisable to follow the manufacturer’s recommendations. These vary from product to product, but generally they address the same issues: application temperature, priming, installation techniques, and compatibility with surrounding materials. Temperature Effects on Peel-and-Stick Flashing MembranesIn general, the rubberized asphalt (modified- bitumen) products start to lose stickiness at around 50°F and will not bond much below 40°F. Unless you are working with a rubberized-asphalt product specifically formulated for low-temperature applications, a butyl-based product is a better choice in cold weather. Very high temperatures can also be problematic for rubberized-asphalt membranes. When subjected to high temperatures and pressure, for example, when squeezed under a dark-colored metal flashing exposed to direct sun, the material will soften and begin to flow. Unless formulated for high temperatures and labeled “hi-temp,” most modified bitumen will begin to soften between 185°F and 210°F. High-temperature formulations can tolerate up to around 240°F, but are generally not as sticky. Substrates: Bonding Flashing Membranes & Tapes to Solid Wood, Plywood, Vinyl, Metal, OSBEach manufacturer specifies which products are safe to bond to and which require priming. Solid wood, plywood, vinyl window flanges, and metal are usually fine as long as they are free of oil and dust. Some manufacturers of rubberized-asphalt tapes recommend that all materials be primed for best performance, particularly in cold weather. Most require that concrete and masonry be primed, and some require the priming of OSB and gypsum sheathing as well. Many published details show asphalt-rubber flashing tapes bonded to asphalt felt and plastic housewraps. While these are rarely listed as suitable substrates in product literature, manufacturers of flashing tapes claim that their products will bond satisfactorily to both these materials as long as they are clean. Do not expect a good bond to dirty housewrap that has been exposed to the weather for a month or to any dirty job-site material. For that reason, it is always best to detail flashings and to layer materials so that they shed water even if the adhesive bond fails. Compatibility Flashing Membranes & Tapes With VinylRubberized-asphalt flashings should not be in direct contact with flexible vinyl flashings. The asphalt compound will draw the plasticizers out of the vinyl, causing the asphalt to soften and flow and the vinyl to become brittle. The rigid polyvinyl chloride (PVC) used in window flanges, however, is generally not a problem. Rubberized-asphalt flashings should also not come into contact with any caulks or sealants unless specifically formulated for that use. Like soft vinyl, sealants may react with the asphalt, causing it to flow and stain the adjacent materials, such as window flanges. Butyl-based flashings are compatible with most construction caulks and sealants, but they should never be installed in contact with any asphalt-based products such as roofing cement or bituminous flashing membranes. These may degrade the butyl and undermine its ability to seal. In these applications, rubberized-asphalt is a much better choice. Applying Pressure is Important in Stick-On Flashing MembranesFlashing tapes must be pressed firmly into place to ensure full contact and a good bond. Some manufacturers recommend using a hard rubber roller for best results. Splashback Protection and Other Uses for Peel-and-Stick Flashing Tapes & MembranesWhile most flashing tapes are used around doors and windows, they can be put to good use wherever water penetration is an issue. Other applications include band joists, deck ledgers, inside and outside corners, and any areas subject to frequent wetting. On wall areas adjacent to a deck or abutting a roof, for example, where splashback or snow buildup is likely to wet the siding, sections of membrane up to 36 inches wide can protect wall assemblies. Make sure to lap all layers of flashing, sheathing wrap, and adhesive membrane so that water is directed to the outside of the building, even if the adhesive bond fails. Caution re Cold-Side Vapor Barrier: Don't Cover Entire Walls with Peel-and-Stick Flashing MembranesWatch out: In cold climates, covering an entire wall section with waterproof membrane will create a cold-side vapor barrier, potentially leading to serious moisture problems and wood decay within the wall cavity. A section of membrane up to 3 feet wide, however, is unlikely to cause problems. -- Adapted with permission from Best Practices Guide to Residential Construction. List of Sources for Flashing Tapes and Membranes - where to buy
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