The best position for a skylight is just below the lap of corrugated roofing.

Skylights for corrugated metal roofs are different from those for shingle or tile roofs. It’s possible for an experienced installer to retrofit flashing and install a typical skylight on corrugated metal.

However, a home improvement enthusiast should install a skylight that’s designed for corrugated roofing. Similar to installing any skylight, the first step is preparing the area of the roof where the skylight will be installed.
1 – Wear work gloves. Place the skylight unit on the roof at the desired location. Align the grooves on the skylight fins with the grooves on the corrugated roofing. Mark an outline along the outer edges of the fins with a felt-tip marker. Set the skylight unit aside.

2 – Deduct the width of the fins on each side of the skylight and mark another outline on the roof to define the area to be cut out. Disregard the larger outline and proceed to the next step.

3 – Remove the screws or nails from the metal roofing at the area inside the smaller outline. Use a power or cordless drill with a screw-tip attachment to remove screws. Use a nail bar and hammer to remove nails.

4 – Install a 1/4-inch drill bit in the drill. Drill starter holes for a jigsaw blade at each corner of the smaller outline. Cut the outline using a jigsaw with a metal-cutting blade. Insert the tip of the blade in a starter hole to cut each side of the outline. Remove the cutout section of roofing.

5 – Cut a horizontal slit in the roofing at the upper corners of the opening. The slits are needed to slip the upper fins of the unit under the existing roof for runoff water. The length of each slit is equal to the width of the corresponding fins on the upper sides of the unit.

6 – Put a tube of roofing-grade silicone sealant into a caulking gun. Apply a generous amount of sealant around the opening on the roof, 1 inch from the cut edges.

7 – Insert the corners of the upper fin on the unit into the slits on each side at the top of the opening. Slide the unit up, until the raised flashing contacts the lower edge of the opening. Press the skylight firmly into place on the roof.

8 – Attach the fins to the roof with 1 1/4-inch self-tapping sheet metal screws at 3-inch intervals. Drive the screws snug with the drill and screw-tip attachment.

That’s it, your metal roof now has a secure, weatherproof skylight.