How to Install a Fixed Skylight in Your Attic

Skylights transform a dark, cramped attic into a bright, usable living space by introducing consistent natural light directly from above. While the prospect of cutting into your roof can be intimidating, the process relies on careful measurement and strict adherence to moisture-barrier installation sequences. Success in this project hinges on two factors: structural integrity and water management. You are essentially creating a new hole in your home's primary defense against the elements, so ensuring the flashing is layered correctly—shingle over flashing at the top, flashing over shingle at the bottom—is the difference between a dry home and a costly long-term leak.

  1. Find your exact opening. Locate the rafters from inside the attic and mark the center point for your skylight. Transfer these marks to the roof deck, ensuring the opening stays at least four inches away from existing rafters, then drill pilot holes at the corners to establish your boundary.
  2. Make the breach. Remove shingles from the marked area using a roofing shovel or pry bar. Cut the roof sheathing along your layout lines using a circular saw set to the exact thickness of the plywood deck.
  3. Build structural support. Install header beams between the rafters at the top and bottom of the opening to support the structure. Secure these with metal joist hangers to ensure they carry the load effectively.
  4. Set the unit square. Place the skylight frame into the opening and secure it to the deck according to the manufacturer's fastening pattern. Ensure the frame is perfectly square by checking diagonal measurements before driving the final screws.
  5. Seal every edge. Install the sill flashing first, followed by the side flashing, and finally the head flashing. Use self-adhering waterproof membrane tape to seal the edges where the flashing meets the roof deck.
  6. Blend roof seamlessly. Re-shingle the area around the skylight, weaving the shingles into the existing roof pattern. Ensure the shingles overlap the flange of the skylight to shed water effectively away from the opening.