How to Install a Round Skylight

Study your ceiling for an appropriate spot to install your round skylight. An area between joists and rafters, with direct ceiling-to-roof access and with no electrical wiring running through it works well.

Trace the outline of the skylight circle on the ceiling where it will be located.

Drive a nail through the ceiling from inside the room right where the center of the skylight will sit. Run a piece of wire up into the hole.

Locate the wire in the attic. Use a plum line per manufacturer instructions to find the center point on the roof directly above the ceiling's center point, where the wire runs through. Drive a nail up through the roof to mark the center. Measure and mark on four sides of the rough opening, specified by the skylight instructions.

Detach shingles on the roof. Mark the circular opening to be cut using the center and side nails as guides.

Cut the roof sheathing along the perimeter of the marked rough opening using a circular saw.

Cut and place 2-inch by 6-inch headers at the top and bottom of where the skylight frame will sit. The header should connect to rafters on either side of the skylight.

Attach the skylight frame per manufacturer instructions. It may have brackets or flanges, depending on the design. A circular skylight may also have a tube.

Remove the protective film from the round skylight.

Apply foam close cell tape along the perimeter seam of the dome, if specified in the manufacturer instructions.

Set the second skylight dome atop the first, spacing it about 1 3/4 inches from the one below. Add foam tape if more space is needed.

Attach the skylight retainer frame using a screw gun, making sure the fit is around the entire skylight.