How to Install a Skylight

Installing a skylight involves cutting a roof opening, framing it properly, and sealing the skylight unit with flashing and weatherproofing materials. This complex project typically takes 1-2 days and requires careful attention to waterproofing.

1. Mark Your Opening Carefully. Choose a spot between two rafters where the skylight will fit without cutting through structural members. Check for electrical wiring, plumbing, or ductwork in the area. Mark the location from inside the attic, then drive a nail through each corner to mark the outline on the roof.
2. Cut Through with Precision. Remove shingles around the marked area, extending about 3 inches beyond your outline. Use a reciprocating saw to cut through the roof sheathing along your marked lines. Remove the cut section and clear any debris from the opening.
3. Reinforce the Structural Opening. Install headers between the rafters at the top and bottom of the opening using 2x lumber that matches your rafter size. Secure with joist hangers or by toe-nailing. If the opening is wider than the rafter spacing, you'll need to cut and frame around the rafters as well.
4. Seat the Frame Perfectly Flush. Set the skylight frame into the opening, ensuring it sits flush with the roof surface. The frame should rest on the roof sheathing, not hang in the opening. Secure the frame to the roof with the screws provided by the manufacturer.
5. Weave Protection Up the Sides. Start at the bottom with the base flashing piece, which goes under the skylight and over the shingles. Work up each side with step flashing pieces, weaving each piece under a shingle course and over the one below. Each piece should overlap the previous one by at least 3 inches.
6. Cap the Top Watertight. Install the head flashing at the top of the skylight, sliding it under the shingles above and over the skylight frame. This piece should extend several inches up under the shingles to direct water away from the opening.
7. Lock Out Water Permanently. Apply roofing cement under all flashing edges and around the skylight perimeter. Replace and install shingles around the skylight, cutting them to fit snugly against the flashing. Apply a final bead of roofing sealant where shingles meet the flashing.
8. Frame Your New Light Source. From inside, install the skylight glazing unit if it's a separate piece. Frame out the interior opening with drywall or wood trim to create a finished light shaft. Paint or finish the interior surfaces as desired.