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Site-Built Windows and Water Management

March 16, 2020

Water management begins with the framing and extends to the WRB

A repair job of a rotted out picture window was a great opportunity for Jake Brutton, of Aarow Building, to explain the water management process. Water management isn't a thing you tack on to the outside of a project, it is a system of construction.

Waterproofing the window rough opening:

  • Slope horizontal framing toward the outside. This is the first step and the last line of defense. If water gets past all of the other layers, this will direct it outside.
  • Liquid flashing products. Aarow uses two types from Prosoco, a joint and seam sealer and a flashing membrane (called Fast Flash).
  • Liquid-applied weather barrier on the sheathing connects to the fast flash in the rough opening.

Water-managed window construction details:

  • The window frame is constructed of Western Red Cedar and stainless steel hardware.
  • The glass is installed from the outside, so the interior stop is a continuous dam behind the glass.
  • The window frame is primed and painted on all six sides before the glass is installed.
  • Flashing tape bridges the space between the window frame and the WRB.
  • Exterior trim, made from PVC, is added over the frame. The trim is gapped at the bottom, so no wicking will occur, and it is back cut along the sides so it will not hold watertight against the flashing tape.
  • Finally, the stops slip in after the glass to hold it in place.

—Jake Bruton owns Aarow Building in Columbia, Missouri. Their YouTube channel covers new construction and remodeling.

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