When JLC published its primer on flexible flashings a decade ago ("Choosing Flexible Flashings," Jun/01), these non-metallic, self-adhered membranes were just becoming common on jobsites. Today, they're everywhere. They have all but replaced felt splines for the edges of finned windows and are now the standard for sealing most other roof and wall penetrations. Ease of use is a big reason: All of these products work well on flat, two-dimensional surfaces, and accordion-style membranes such as DuPont's FlexWrap or Typar's Flashing Flex will conform to three intersecting surfaces, such as the corner of a window opening.Manufacturers have made it a...

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