Techniques for installation of “punched” windows and doors have been evolving continually over the last two decades. For many years, the accepted standard involved four strips of flexible flashing integrated with a nailing fin and the water resistive barrier (WRB) at the window perimeter. This concept was easy to understand and implement because the window fins, flashings and the WRB were typically all in the same plane. It is amazing, however, that so many designers and builders were still able to get it wrong.
Up until the 1990s, flexible flashings were typically made of laminated kraft paper treated with asphalt. Chronic exposure to water often resulted in disintegration and resulting structural damage. The introduction of plastic, rubber and modified bitumen flexible flashings, mostly of the “peel and stick” (self-adhesive) variety in the decade of the 1990’s improved durability vastly.
Read a window and door installation guide by our founder, Tom Butt, here: