How to Properly Flash a Window

Last summer we hired a new crew member. When it came time to hang windows, I clamped a GoPro to the fascia and recorded the installation. This can be used as a reference for new crew members, but it can also be used to show potential clients our methods.

We have used Huber Engineered Wood Zip System for 11 years and now. One major reason we like this system is the simplicity of flashing openings and penetrations. Managing bulk water is very important for the longevity of the structure, but it also lowers our risk.

What I like about this method of properly flashing a flange window, is how easy it is. The acrylic tapes used are pressure sensitive, so make sure you always roll the tape. Basically the steps are as follows:

1) Flash the sill pan. I use 6” tape and then pieces of Stretch tape in the corners to make a sill pan.

2) Caulk the back of the flanges and install the unit.

3) Tape the legs (sides).

4) Tape the header (top)

5) Roll all the tape for proper adhesion

In this case the window will get trimmed, metal head flashing installed and then taped the wall. The window will later get caulked at the sill inside the house. We have installed windows this way for years and blower door tested over a hundred of these installations. They are air tight and if they are air tight they are water tight.