Skylights and Roof Replacement: Replace or Reflash?

Replacing Your Roof? Do Not Forget About the Skylights

A roof replacement involves much more than installing new shingles or tiles. Every opening in the roof—including plumbing vents, chimneys, exhaust vents and skylights—must be properly integrated into the new roofing system.

Skylights deserve special attention because they combine several components that can eventually wear out:

• Glass or acrylic glazing
• Exterior frames
• Gaskets and seals
• Flashing
• Underlayment
• Curbs or mounting systems
• Interior finishes

A skylight that has not caused a noticeable leak may still be nearing the end of its service life. Reusing it without evaluating its age and condition can create an avoidable weak point in an otherwise new roof.

Why Roof Replacement Is the Best Time to Evaluate Skylights

Replacing a skylight after a new roof has already been installed usually requires removing or disturbing the surrounding roofing materials.

That means additional labor, new flashing and the possibility of damaging recently installed shingles or underlayment.

During a complete reroof, the area surrounding the skylight is already being opened. The roofing contractor can inspect the skylight, remove the old flashing and evaluate the curb or roof deck without unnecessarily disturbing a finished roof later.

Skylight manufacturer VELUX advises roofing professionals that skylights more than 20 years old may be more susceptible to frame damage during the reroofing process, which can contribute to leaks or other issues. (Velux USA)

Age alone does not determine whether every skylight must be replaced, but it should be part of the conversation.

Option One: Keep and Reflash the Existing Skylight

A relatively new skylight may be reused when it is in good condition and compatible with the new roofing system.

The contractor should evaluate:

• The condition of the frame
• The glass or acrylic
• Evidence of condensation between panes
• Cracked or deteriorated seals
• Corrosion
• The mounting curb
• Interior water stains
• The roof pitch
• Compatibility with available flashing systems

Reusing the skylight should not mean reusing worn-out flashing.

The existing roofing materials and flashing should generally be removed so the area can be properly rebuilt with compatible underlayment and a new flashing system.

Option Two: Replace the Skylight During the Reroof

Replacing the skylight may be the better decision when:

• The skylight is approaching or beyond its expected lifespan
• The glazing is cracked, cloudy or discolored
• Moisture appears between glass panes
• The frame is deteriorated
• The skylight has a history of leaking
• Replacement parts are unavailable
• The existing unit is not energy efficient
• The skylight does not work properly
• The mounting system is incompatible with the new roof
• You want to upgrade from a fixed unit to a venting model

Replacing the roof and skylight together allows the roofing components to be treated as one coordinated system.

Why Proper Skylight Flashing Matters

Flashing directs water around the skylight and back onto the roof surface.

A well-designed flashing system does not depend entirely on exposed caulk or roofing cement. Factory-produced skylight flashing kits are designed to work with specific roof materials, mounting methods and roof pitches.

VELUX explains that its flashing kits are designed to shed water without relying on sealants that can deteriorate over time. The company offers different systems for shingles, shakes, tile and curb-mounted applications. (Velux USA)

The correct system depends on several factors:

• Deck-mounted or curb-mounted construction
• Asphalt shingles, tile, metal or another roof material
• Roof slope
• Skylight manufacturer and model
• Thickness and profile of the roofing material

Using a generic flashing detail around every skylight can create drainage and compatibility problems.

Avoid a Sealant-Only Repair

Applying additional caulk around a skylight may temporarily slow an active leak, but it should not be treated as a complete replacement for properly installed flashing.

Sealants expand, contract, dry out and separate as the roof is exposed to sunlight and temperature changes. Water can also enter beneath the roofing material or behind the skylight frame, where surface caulking may not reach the actual opening.

Proper skylight installation normally includes underlayment around the opening, compatible flashing and roofing materials installed in the correct sequence. GAF recommends factory-manufactured step-flashing systems for skylights and detailed protection around the opening. (GAF)

Is the Skylight Actually Leaking?

Water stains around a skylight do not always originate from exterior rain.

Possible causes include:

• Condensation on the glass
• Excess indoor humidity
• Poor bathroom or kitchen ventilation
• An uninsulated skylight shaft
• Roof leaks occurring farther upslope
• Cracked glazing
• Failed flashing
• Damaged underlayment
• Debris preventing drainage

A professional inspection can help separate condensation problems from an exterior roofing leak.

This distinction matters because replacing flashing will not solve indoor moisture problems, while reducing indoor humidity will not repair damaged exterior flashing.

Questions to Ask Your Roofing Contractor

Before your roof replacement begins, ask:

1. How old are the skylights?
2. Are they deck-mounted or curb-mounted?
3. Is there evidence of previous leaking?
4. Can compatible replacement flashing be obtained?
5. Are the frames and glazing still in good condition?
6. Will the existing skylights be removed during reroofing?
7. What underlayment will be installed around them?
8. Does the manufacturer recommend replacement?
9. Will the skylight work with the selected roofing material?
10. How will the skylight work affect the roof warranty?

These decisions should be made before materials are ordered and the roofing project begins.

Coordinate the Entire Roofing System

A new roof may be designed to perform for decades. Reinstalling an old or deteriorated skylight can create a mismatch between the expected lifespan of the roof and the expected lifespan of the skylight.

That does not mean every skylight must automatically be replaced. It means each unit should be inspected and included in the project plan.

Rocket Roofing can evaluate the roofing materials, skylight flashing, surrounding roof deck and other penetrations as part of a professional roof inspection or replacement proposal.

Contact Rocket Roofing before beginning your Southern California reroofing project to determine whether your skylights should be retained, reflashed or replaced.