When should skylights be replaced, and how is it done?
Short answer. Replace skylights when the glass fogs between panes, the dome is cracked or yellowed, the frame is rotted, leaks return after reflashing, or the unit is about as old as the roof being replaced. Replacement means removing the shingles around it, taking out the old unit and flashing, adjusting the framing if the size changes, installing the new unit with membrane and a flashing kit, then reshingling and finishing the shaft.
The replacement, step by step
- Choose a new unit that fits the same rough opening when possible, which avoids reframing.
- Remove the surrounding shingles and the old flashing.
- Take out the old unit or dome, and the curb if you are converting to a deck-mounted skylight.
- Repair or adjust the framing and decking, and replace any rot.
- Wrap the opening with self-adhered membrane.
- Set the new unit square and fasten it as the maker specifies.
- Install the flashing kit: apron at the bottom, step flashing up the sides with each course, and head flashing at the top.
- Reshingle and seal any exposed fasteners.
- Inside, repair the drywall in the shaft, then trim and paint.
Best timing
The ideal moment is a roof replacement: the shingles are already off, the crew is on the roof, and the new skylight is flashed into fresh underlayment. Replacing a skylight a few years after a new roof means cutting into new shingles and trying to match them.
Changing the size
Going larger usually means cutting rafters and adding headers, which may need a permit and should never be done on trusses without an engineer's design. Going smaller means framing in and decking over part of the opening. Swapping a large skylight for a tubular unit is another option.
See skylights and roof replacement and roofing permits in Georgia.