Flanged window installation

What’s the best way, hands down, to flash a flanged vinyl window during new construction installation?


When the nailing flange (fins or perimeter casing) is attached directly to the sheathing or framing, install flashing as well as sealant. Improper or nonexistent flashing can allow moisture to permeate the structure and ultimately result in water damage. Use 30 lb. felt, bituminous impregnated craft paper, or standard sheet-metal flashing (aluminum or galvanized steel). Twelve-inch width is recommended; nine-inch is the minimum.

Flashing techniques vary with the style of window or patio door and the type of opening; however, there are basic flashing principles that always apply. Start from the bottom and work to the top. Install the first strip (sill flashing) horizontally across the bottom of the rough opening and extend it beyond the edges of the opening by a distance exceeding the width of the material. Next, extend vertical strips (jamb flashing) from above the top of the rough opening to below the bottom of the sill flashing. Finally, after the window is secured, install the head flashing across the top of the window, extending beyond the jamb flashing on each side. The top edge of the flashing is attached to the structure, and the bottom edge is placed over the head fin.

If you have a subscription to JLC I think they covered that in one of the most recent issues. The information might be available on their website. JLConline.com I think.

http://www.badstucco.com/repair2.html Minus the stucco.
http://www.badstucco.com/properflash/properflash.html Finished product!
The windows no longer have sills and the flashing under the bottom nail fin is just as crucial as the flashings at the head of the windows! IMO It takes flashing in three places when the windows are trimed out.

Defently do not do this!

Best way to install and flash a window is per the manufacturer’s recommendations.

Installation .pdf example of a flanged vinyl window:


What about kicking the water back out over the cladding! Most window mfgs. do not address that problem.

Thank you all, Gentlemen. I used this question (and one earlier this morning about water heater exhaust vents) to demonstrate to a first-day HI class the power of internet message boards. Needless to say, the results are impressive.

Thanks for making me look good to these students/future inspectors!