How to Install a Round Window
Add architectural interest to your home by framing for a round window. We'll show you how to install one yourself.
Framing for a round, octagonal, oval, or half-round window starts the same as for a standard window. Cut and frame a rectangular opening to accommodate the window at its greatest dimensions—in this case the top of a half-round window's arc.
The installation of the round window shown here includes sheathing with self-adhesive flashing tape. There is no metal drip cap over the rounded top; the joint between the curved brick molding and the siding is simply caulked. For a more weatherproof installation, have a roofer or a sheet metal shop make up a curved drip cap to fit your window.
With a flanged window, it often makes sense to remove a section of siding so pieces that overlap the flange can be woven in. For curved cuts through heavy materials, a reciprocating saw is nearly indispensable. You can rent one if you don't own one.
You'll need roughly 3 hours to frame and install a half-round window in a rectangular opening. Before you begin, cut and frame the opening on the inside, but do not cut the sheathing.