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In this video, This Old House general contractor Tom Silva installs a new skylight into an existing opening.

How to Replace a Leaking Skylight

  1. Use a flat pry bar to remove roof shingles, starting three or courses above the skylight.
  2. Then pry up roof shingles from each side of the skylight, revealing the step flashing.
  3. Unscrew and remove the counter flashing from around the skylight.
  4. Pry off the step flashing from the sides of the skylight.
  5. Unscrew and pry off the head flashing from the top end of the skylight.
  6. Use a utility knife to slice through the ice-and-water membrane around the skylight curb.
  7. Peel back the membrane to expose the metal brackets holding the skylight to the roof deck.
  8. Unscrew the brackets from the skylight curb, then pull the skylight from the opening.
  9. Slice through the membrane along the bottom to free the skylight from the roof.
  10. Before installing the new skylight, mount the solar-powered window shade and the interior wooden trim package.
  11. Nail vinyl strips around the perimeter of the roof opening to cover the exposed edges of the drywall.
  12. Set the new skylight into place, centered in the roof opening.
  13. Secure the skylight by driving 2-inch galvanized ring-shank nails through the mounting brackets and into the roof deck.
  14. Apply self-sealing ice-and-water membrane along the bottom of the skylight.
  15. Lift the rubber gasket attached to the lower end of the skylight, and slip into place the bottom flashing.
  16. Nail the bottom flashing to the sides of the skylight curb and down to the roof deck.
  17. Cover both sides of the skylight and bottom flashing with continuous strips of self-sealing membrane.
  18. Reinstall the roof shingles removed earlier, starting at the bottom and working up the roof.
  19. Along the sides of the skylight, install a piece of step flashing in between each course of shingles. Nail the step flashing to the skylight curb, not to the roof deck.
  20. Continue to install roof shingles, making sure you don't nail through the step flashing.
  21. Install counter flashing around the perimeter of the skylight, starting at the bottom.
  22. Then attach counter flashing along each end and finally across the top of the skylight.
  23. With the counter flashing installed, screw the head flashing into place. Be sure the upper edge of the flashing is tucked beneath the roof shingles.
  24. Install the remaining shingles above the skylight.
  25. From below test the operation of the solar-powered window shade.