Framing, House Wrap and Nailing Fin on New Construction Windows

Work from the sill up, because rain finds the lowest edge first, and the breakdown sitting on austin new windows le mistral houston lists the layers in that order. The goal of the whole sequence is that every piece laps over the one below it, like shingles, so water in Austin, TX that gets behind the siding runs down and out instead of into the wall. A new construction window left to a rushed day usually gets the order wrong at the sill.

Start with the rough opening

The framing crew leaves an opening a little larger than the window, with a flat, level sill plate and plumb jack studs. Check it before the wrap goes on. A sill that slopes inward sends water toward the house, and a rough opening a quarter inch tight means the window gets forced into place and the frame bows. The window wants a clear gap around it for shims and sealant.

Sill pan first

A sill pan is a flashing or a folded tape layer that catches any water getting past the unit and turns it outward. It goes in before the window does. Peel and stick membrane lapped up the jack studs at the corners makes the pan watertight at its ends. This is the layer most often skipped, and it is the one that saves a wood sill from rot in a wall on the stormy side of the house.

House wrap and the nailing fin

The house wrap is cut in a modified Y pattern at the opening, the side flaps folded into the jambs and the head flap lifted out of the way. The nailing fin is the thin flange around the edge of a vinyl window, a fiberglass window or a clad window, and it sits on a bead of sealant over the sill pan before it is nailed. Slider and awning units use the same fin, and a casement may use a slightly different flange.

Flashing tape order

Tape goes on in the order that water would flow: sill first, jambs second, head last. The head tape laps over the top of the fin, and the wrap flap drops down over the head tape. Each strip needs to be rolled firm with no wrinkles. Insulated glass units with a warm edge spacer last longest when the frame stays dry, because seal failure shows up first where moisture sits against the edge.