Your Roof Is Coming Off. Should the Skylight Come Out Too?

A roof replacement forces a decision that is easy to miss in the larger proposal: what happens to each skylight? The choices are not simply keep it or remove it. A skylight can remain in place and receive new flashing, it can be replaced with a new unit, or the opening can be closed and roofed over. The right answer depends on the skylight's age, design, glass, curb and leak history. Make that decision before the shingles are ordered. Changing it after the crew has opened the roof adds labor and can delay drying the house in.

Town roofing

Chesterfield houses include skylights installed during original construction, units added during later remodels and roof windows placed over finished upper rooms. Two skylights that look similar from the driveway may connect to the roof in different ways.

A deck mounted skylight attaches directly to the roof deck. A curb mounted skylight sits on a raised box, called a curb, built above the roof surface. Both require a flashing system that directs water around the opening. That system usually includes sill flashing at the bottom, side pieces that work with individual shingle courses and head flashing at the top. An adhesive membrane beneath the visible metal provides another layer of protection.

Reusing the skylight should not mean leaving all of the old metal in place and cutting new shingles around it. A proper reroof requires enough access to inspect the surrounding deck and rebuild the water path. The written scope should identify whether the contractor will install a new flashing kit, reuse any existing components or replace the entire unit.

St. Louis weather makes that detail important. Wind driven rain can push water against the uphill side of a skylight. Hail can mark cladding or damage an acrylic dome. During the freeze thaw cycle, water held beside poorly fitted flashing can freeze, expand and open a small route into the roof assembly. Ice damming at an eave can also back water uphill, although a skylight farther up the slope should not automatically be blamed for moisture that began below it.

A ceiling stain near a skylight does not prove the skylight itself failed. Water may enter at a nail, vent or flashing joint farther upslope and travel along decking or framing before it appears indoors. Condensation can also collect on cold glass or an uninsulated shaft. Before buying a new unit, ask the roofer to distinguish a glazing failure from a flashing failure and an indoor moisture problem.

Signs that favor replacement

• The insulated glass has fog or moisture trapped between its panes.
• The frame, curb or surrounding deck shows decay.
• The unit has cracked glazing, damaged cladding or brittle plastic.
• Replacement flashing is unavailable or incompatible with the new roof assembly.
• The skylight has leaked after more than one competent flashing repair.
• The unit is old enough that another roof is likely to outlast it.

Age alone does not settle the question, but it changes the economics. Saving an older skylight during the reroof may avoid one expense now. If that unit fails several years later, replacing it can require removing sound shingles, rebuilding flashing and matching a roof that has already weathered. That second mobilization is usually less efficient than doing the work while the deck is exposed.

Signs that reuse may be reasonable

• The glass seal is clear and intact.
• The frame and curb are square, dry and solid.
• The manufacturer still supplies a flashing kit for the unit and roof type.
• The skylight has no recurring leak history.
• The opening and shaft still suit the room below.

A roofer should still photograph the unit, the exposed curb and the deck around it. Those photographs give you a record of what was found before underlayment and shingles covered the area.

What it costs

The cost difference is driven by more than the price of the skylight. Labor changes with the unit type, roof pitch, height, access and interior finish. A straightforward replacement using the existing opening is different from resizing an opening or repairing a damaged light shaft. Motorized shades, venting hardware, electrical work and interior drywall are separate decisions.

Ask for three numbers when the options are genuinely available: the price to reflash and retain the existing unit, the price to replace it in the same opening, and the price to close the opening. Each price should state what happens to the underlayment, curb, shingles and interior finish.

Closing a skylight is not just a matter of laying shingles across the top. The opening needs structural framing and roof decking that match the surrounding deck. Underlayment must cross the repaired area continuously. Inside, the shaft generally needs insulation, air sealing, drywall and paint. A roofing quote may cover the exterior work but exclude the finished ceiling below, so that boundary belongs in writing.

Unexpected deck damage is another cost line. Water can soften sheathing immediately below a skylight while the visible frame still looks acceptable. The proposal should state the unit price for replacement decking and explain how additional work will be approved. That is more useful than a vague allowance.

If the existing roof uses older three tab shingles, consider the larger roof decision before spending heavily on an isolated skylight repair. Once a three tab roof is around 20 years old, brittleness, discontinued colors and limited remaining service life can make repeated repairs poor value. The exact condition matters more than the birthday, but disturbing brittle tabs around a skylight can turn a small flashing job into a larger repair.

Municipal requirements also depend on the property address and the work being performed. Chesterfield and other permit desks across St. Louis County do not all administer roofing work in exactly the same way. Confirm which authority serves the address and whether replacing, resizing or closing the skylight changes the permit scope. The contractor should name the responsible permit desk rather than treating all St. Louis County addresses as one jurisdiction.

What to ask

1. Is this skylight deck mounted or curb mounted? The answer determines how it connects to the roof and which flashing system is appropriate.
2. Are you installing a complete new flashing kit? Ask for the manufacturer and product identification in the scope.
3. Will membrane run around the entire opening? The scope should describe the underlayment at the sill, sides and head, not just the visible metal.
4. What condition is the insulated glass seal in? Fog between panes is different from condensation on the room side of the glass.
5. What happens if the curb or deck is rotten? Get the repair rate and approval process before work starts.
6. Does the price include interior work? Drywall, trim, paint, wiring and shade installation are often outside a roofing scope.
7. Who supplies the skylight and verifies its size? Model numbers and rough opening dimensions should be checked before the roof is opened.
8. Will I receive photographs? Ask for images before removal, with the surrounding deck exposed and after the flashing is complete.

Also ask how the skylight work affects the two separate warranties involved. The skylight manufacturer covers its product under its written terms. The roofing contractor is responsible for the installation under the contractor's written terms. Those obligations are not interchangeable. Keep the model number, flashing kit information, photographs, invoice and installation instructions with the roof paperwork.

If several skylights are involved, put each one on the proposal separately. Label them by room or roof plane, such as primary bathroom north slope or kitchen rear slope. A single line reading reflash skylights does not tell you which units stay, which components change or how a damaged unit will be handled.

Keys Roofing can inspect the skylight area, photograph what is visible and put the proposed roof work, measurements and materials in writing. Keys installs Atlas and Malarkey shingles. To arrange an inspection at a Chesterfield address, call (314) 220-2333. Before signing, make sure the scope names the disposition of every skylight: retain and reflash, replace in the existing opening, or remove and close.