Skylight Replacement: Flashing Kits, Roof Work, and Interior Finish

Compare skylight bids by system, opening, and finish scope. A replacement is more than placing new glass in an old curb: the contractor may remove surrounding roofing, underlayment, flashing, and trim before installing the new unit. VELUX says replacement involves measuring the existing skylight, removing the old unit and surrounding materials, then fitting new underlayment, flashing, skylight, and roofing (VELUX replacement process).

The four measurements that control the quote

Measurement or condition	Why it matters	Evidence to request
Existing opening	Determines whether a same-size replacement is possible	Interior finished opening and exterior frame photos
Roof pitch	Flashing kits are engineered for specific pitch ranges	Pitch recorded on the proposal
Roof covering	Shingles, shakes, tile, and metal need different flashing	Product and flashing-kit model
Mounting style	Deck-mounted and curb-mounted units have different interfaces	Manufacturer model or written description

VELUX specifically notes that correct roof pitch is essential for drainage and that each skylight and flashing kit has pitch requirements (VELUX pitch guidance). Do not accept “standard flashing” without the roof pitch and covering written down. If the roof covering is thick shake or tile, the quote may need additional or pliable flashing components.

Flashing is part of the unit decision

VELUX describes its flashing kits as interlocking with roofing material and says the kits must be purchased and installed properly for its warranty (VELUX flashing systems). A quote that lists the skylight but omits the kit, adhesive underlayment, or roof-cover replacement is incomplete. Ask whether the installer is using the manufacturer’s specified kit or a custom curb detail and who will warrant the interface.

For a leaking older skylight, request two scopes: a flashing-only investigation, if the unit and frame are sound, and full replacement. Sealant around the perimeter is not the same as rebuilding the flashing path. The decision turns on frame condition, glazing failure, shaft damage, and roof age. If several skylights sit in a roof that is already being replaced, compare the incremental removal and flashing work against a later standalone visit.

Interior finish belongs in its own line

Roof work can leave the light shaft, ceiling drywall, paint, trim, or insulation requiring repair. Have the roofer document whether the shaft is dry and sound, then obtain restoration pricing separately if needed. EPA says porous materials that remain wet can be difficult to clean fully, and moisture problems should be corrected before finish work (EPA mold cleanup guidance).

Ask for a completion test: photos of the finished flashing, confirmation that surrounding roofing is secured, and a clear warranty statement. Keep model numbers and installation records. Warranty language is product-specific and may exclude failures caused by incorrect pitch, unapproved alterations, or workmanship outside the manufacturer’s system.

A skylight product price needs the matching flashing, roof work, interior finishing, and installation added before it can become a project budget. Unit size, mounting style, roof covering, access, interior shaft depth, and restoration needs produce different jobs. Use the table above as a bid checklist and require any allowance for concealed deck or shaft damage to be stated separately.