Skylight Units and How Each Is Mounted
The type you pick decides how big a hole goes in the roof, whether the ceiling below needs a framed light shaft, and how much flashing there is to get right.
Fixed Skylights on a Deck-Mount Frame
A fixed skylight doesn't open. A deck-mounted unit carries its own frame and fastens straight to the roof sheathing, sitting low against the shingles, and the maker's flashing kit locks into that frame. It's the usual choice on a pitched shingle roof. On a low-slope roof the code adds a step: below a 3-in-12 pitch, a unit skylight has to sit on a curb at least 4 inches above the roof unless the manufacturer's instructions say otherwise. Inside, the opening between rafters becomes a drywalled light shaft down to the ceiling, which is often the larger share of the carpentry.
Venting Skylight Units
A venting skylight has a sash that opens, by hand crank, electric motor or a solar-powered motor, to let hot air out at the top of a room. Bathrooms, kitchens and upstairs halls are the usual spots. Some motorised units come with a rain sensor that closes the sash at the first drops. The flashing is the same as a fixed unit, but there's a hinge and a weatherstrip to wear out, and a motor needs power run to it. If you want a powered unit, ask whether the electrical hookup is part of the roofer's bid or a separate electrician's job.
Tubular Daylighting Devices
A tubular daylighting device, often sold as a sun tunnel or solar tube, is a small dome on the roof feeding a mirror-lined tube that ends in a round diffuser in the ceiling. No rafter gets cut, and the tube can bend around attic obstacles, so it suits closets, hallways and interior bathrooms that a framed skylight can't reach. The roof part is a small round flashing collar under the shingles. The code treats these units like other skylights for testing and labeling, so the dome should carry a performance label just like a full-size skylight.
Skylight Replacement and Reflashing
On an older skylight, check the flashing before blaming the glass. A fogged unit, cracked dome or leaking frame usually means replacing the whole skylight with its matching flashing kit; patching old aluminum flashing with sealant rarely lasts. A curb-mounted unit can sometimes take a new skylight on the same curb, which keeps the interior finish intact. Either way, the shingles around the unit come up, the curb gets a fresh wrap of self-adhered membrane, and new step flashing goes in course by course. Under the 2024 IRC, a unit skylight flashed to its manufacturer's instructions doesn't need the cricket that a wide chimney would.
Why Thornton homeowners call Thornton Expert Roofing
- Free written estimate, no obligation
- One independent local contractor per request, not a call list
- A written contract with the price and materials before any work, as Colorado law requires
- Nothing charged to homeowners for the referral
Skylight Installation Cost and Service Life
HomeGuide's published averages: $1,600 to $4,200 to install a new skylight, $800 to $2,400 to replace an existing one. The gap is mostly the framing and drywall: a new skylight means cutting rafters or adding headers and building the light shaft, while a replacement reuses the opening. Tubular units sit at the low end because there's no shaft to build. Motorised venting units, larger sizes, laminated glass and a steep or tall roof push a price up.
Ask for the estimate to split the roof work (cutting the opening, the unit, the flashing kit and shingles) from the inside work (framing the shaft, drywall, tape and paint). Some roofers stop at the ceiling and leave the interior finish to you or another trade, and two bids only compare fairly when both cover the same scope.
InterNACHI rates skylights at 10 to 20 years. The shingles around them often outlast that, which is why the best time to replace an older skylight is during a re-roof, when the flashing is coming off anyway. If a roof is near the end of its life, it's worth planning the skylight and the roof replacement together rather than paying for flashing twice.
Skylight Glazing, Labels and Curbs in the 2024 IRC
Thornton applies the 2024 International Residential Code to permit applications submitted from July 1, 2026. Its skylight section (R324.6) sets the details a homeowner can check on a quote:
Glazing
Skylights can use laminated glass, fully tempered glass, heat-strengthened glass, wired glass or approved rigid plastics. Laminated glass needs at least a 0.015-inch interlayer for panes up to 16 square feet that sit no more than 12 feet above a floor, and thicker for larger or higher panes.Screens
Tempered and heat-strengthened glass usually needs a broken-glass retention screen below it, with exceptions for small, low tempered panes. Laminated inner panes need no screen.Labels
Unit skylights and tubular daylighting devices must be tested by an independent lab and labeled with the manufacturer, a performance grade and the inspection agency, under AAMA/WDMA/CSA 101/I.S.2/A440.Curbs
Below a 3-in-12 pitch, a 4-inch curb unless the maker's instructions say otherwise.
Ask the roofer to name the exact skylight model on the estimate, so you can look up its label and glazing before work starts.
Skylights Under Front Range Hail
A skylight is a hole in the roof facing straight up, in the part of North America that sees large hail most often (the hail climate is covered on hail damage roof repair). Laminated glass holds together when it cracks; plastic domes on older units can split or craze. After a storm, check skylights from inside for cracks and from the attic or light shaft for water. A cracked skylight needs a temporary cover until it's replaced; see emergency roof repair. Leaks around other roof penetrations are covered under roof leak repair.