This story shows you how to install a round window.
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 like the one shown, 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.
With a rectangular opening cut, about 3 hours to frame and install a half-round window
Tape measure, hammer, drill, scribing compass, reciprocating saw, circular saw or power miter box, stapler
Measuring; framing; using a circular saw, jigsaw, and reciprocating saw
Cut and frame the opening on the inside, but do not cut the sheathing.
Round-topped window, cardboard for a template, 2x4s for angled framing pieces, roofing felt or building paper, self-stick flashing tape, nails and screws
Remove the siding so you can weave it in. Add flashing, working from the bottom up. Install the window. To mark the new siding, scribe with a compass. To keep the desired overlap, set each piece on partially driven guide nails. Hold the compass level as you mark.