Skylight Maintenance: Preventing Leaks and Condensation

A twice-a-year skylight checklist

From inside the room

• Look at the drywall in the light shaft, especially the upper corners, for brown rings or bubbling paint.
• Run a finger along the bottom of the frame after a cool night for moisture or dark marks.
• On venting units, open and close the sash fully, test the crank or remote, and clear the insect screen.
• Test blinds and rain sensors on electric or solar models, and swap remote batteries before the wet season.

From outside, without walking the roof

• From the ground or a ladder at the eave, look for leaves, needles or seed pods piled on the uphill side of the curb.
• Check the dome or glass for cracks, crazing or yellowing, and the frame for gaps or rust.
• Look for lifted shingles, cracked tiles or missing flashing pieces around the skylight.
• Clear the gutters below the skylight so overflow does not back up at the eave.

Plan one check in early fall, ahead of the rains, and one in spring after the last big storm.

Skylight care through the San Gabriel Valley year

The twice-a-year checks above fit around the local weather. Here is how skylight care lines up with the seasons in Rosemead and the foothill cities, where most rain falls between November and March and Santa Ana winds can blow from October on.

How do you clean a skylight without damaging it?

Glass and plastic need different handling. Acrylic domes scratch easily, and harsh cleaners speed up the crazing that sun already causes.

Interior glass gets the same soft-cloth treatment. Outside, rinsing from a ladder at the eave works on many single-story homes. If the skylight sits high on the roof, have it cleaned during a roof service instead of walking out to it.

Is it condensation or a real leak?

Condensation is the most common winter skylight complaint, and it is not a roof problem. Humid indoor air meets glass chilled by a clear night, droplets spread across the inner surface, and they run to the frame and drip. These steps reduce it:

• Run the bathroom fan during showers and for a good while after.
• Use the range hood when cooking under a kitchen skylight.
• Crack a venting skylight open for a few minutes after showers or cooking.
• Keep the shaft walls insulated on the attic side so the shaft stays warm.
• Consider double-pane low-E glazing if a single-pane dome drips every winter.

A real leak follows the weather instead. It shows up during or after rain, often at one corner, and the stain grows storm by storm. That pattern calls for a skylight repair visit.

What we notice on skylights during SGV roof visits

Big trees create the most skylight debris. In Pasadena and San Marino, mature oaks, sycamores and pines drop leaves and needles that pile against skylight curbs on the uphill side. That pile stays damp, rots the curb wood and steers rain under the flashing. Clearing it twice a year is the cheapest leak prevention there is.

Sun damage shows up first on south and west roof faces, where acrylic domes turn brittle and sealant joints split. On tile roofs the usual culprit is foot traffic: a satellite or solar installer cracks tiles near the skylight, and rain reaches the underlayment through the gap.

The tile and slate roofs in those older neighborhoods also deserve care in how the check is done. We look from a ladder first and step only where the roof can take weight.

What to handle yourself and what to leave to a roofer

Homeowners do the most useful skylight maintenance themselves: watching the shaft for stains, running fans, rinsing glazing from the eave and keeping gutters clear. Where a roofer adds value is anything that touches the seal between the skylight and the roof. A bead of store-bought caulk over old roof cement often traps water behind it, and the next repair starts with scraping it all off.

The honest trade-off runs the other way too. A newer glass skylight on a single-story shingle roof with no trees overhead may need nothing more than your own checks for years. A skylight on a second story, on tile, or under oaks and pines is where a yearly look during a roof visit pays for itself.

Why is walking near a skylight so risky?

A skylight looks like part of the roof, but most units are not built to carry a person. Federal workplace safety rules treat a skylight as a hole in the roof: OSHA requires roofers working more than 6 feet above a lower level to be protected from falling through one by a cover, a guardrail or a personal fall arrest system. That rule exists because people have fallen through domes they stepped on, sat on or leaned against.

• Never step, kneel or lean on a dome, a glass unit or a tubular skylight lens, even one that looks solid.
• Treat old acrylic as brittle. Sun-aged domes can shatter under a hand braced against them.
• Do your checks from a ladder at the eave, set at a steady angle and extending about 3 feet above the roof edge.
• Stay off the roof when it is wet, dusty or covered in leaves and needles, and never walk on clay or concrete tile.
• If a skylight sits where people regularly work on the roof, ask about a fitted screen or guard over it.

Roofers clip into an anchor before working near a skylight. A homeowner without that gear gets the same information from the eave and from the room below.

Signs that maintenance has become a repair

Some findings mean the skylight needs more than cleaning:

• A crack or hole in the dome, even a small one.
• Fog trapped between glass panes that will not wipe off.
• Soft or dark wood at the curb or inside the shaft.
• Flashing held on only by sealant, or sealant that has pulled away.
• Water stains that grow after each storm.

Small items can often be folded into general roof maintenance. Larger ones call for reflashing or a new unit, and if the skylight is near the end of its life, compare the cost of replacing the skylight against another repair.

Keep it clear and keep it dry

Most skylight leaks begin with debris, dried sealant or a crack nobody noticed in time. Two short checks a year, gentle cleaning and good indoor ventilation keep a skylight working through the rainy season. If you would rather not climb, or you spot something from the list above, call (725) 745-8803 to set up a skylight check with photos of what we find.