Skylight leaks in Manassas: repair or replace

A skylight that drips in Manassas is usually leaking at the flashing or the seal, not through the glass. If the frame and glass are sound, a reflash fixes it. If the frame is warped or the glass has failed, replacement is the better move. The roofer decides by looking at the unit, the curb and the shingles around it.

Why skylights leak on Manassas roofs

Summers here are hot and humid, and the sun bakes the metal flashing and rubber gaskets around a skylight until they dry out and shrink. The gaps that open are small, but wind-driven rain finds them. Then winter freezes and thaws pull the sealant loose a little more each year.

Thunderstorms add to it. Heavy rain arrives sideways, and it pushes water up under the upper edge of the flashing, where a skylight is most exposed. A roof with a low pitch drains slower, so water sits against the frame longer.

Tall trees in the older neighborhoods of Manassas drop leaves and needles into the corner where the skylight meets the roof. That debris holds moisture against the flashing and keeps the corner damp long after the rain stops. A damp corner rots sealant and rusts nails.

Shingle age matters too. When the shingles around the skylight are worn, they curl and lift, and the flashing that was tucked under them no longer lies flat. Sometimes the skylight is fine and the roof around it is the real problem.

Signs the leak is at the skylight

A brown ring on the ceiling around the light well is the common sign. Drips that show up only during a hard, windy rain point to flashing. Drips that come after every rain, even a light one, point to a failed seal or a cracked frame.

Fogging between two panes of glass is a different problem. That means the sealed glass unit has failed, and no amount of caulk will clear it. Condensation on the inside surface of a skylight in winter is also not a leak. It comes from indoor humidity meeting cold glass.

Look at the attic side if you can reach it safely. Wet insulation, dark stains on the rafters or damp drywall around the shaft show where water is getting in. Do not climb onto a wet or steep roof to check. The roofer can find the entry point from the top.

Repair costs

Reflashing a skylight in Manassas typically runs $400 to $1,500. The low end covers new sealant and a few replaced flashing pieces on an easy-to-reach unit. The high end covers a full reflash with new step flashing, a new curb cap and some replaced shingles around the opening.

What moves the price is roof pitch, how many shingles must come off, whether the skylight sits near a valley or chimney, and whether the decking underneath has soaked through. Rotted decking costs $3 to $6 per square foot to replace, and it is the most common surprise once the old flashing comes off.

Repair is a good choice when the glass is clear, the frame is straight and the skylight is not far past the age of the roof around it. A skylight that was installed with the current roof and has a flashing kit made for that model often reflashes well.

Replacement costs

Replacing a skylight in Manassas typically runs $1,000 to $3,500. A fixed unit of standard size sits at the low end. A venting model, a larger opening, a solar-powered opener or a framed shaft that needs reworking pushes the job toward the high end.

Replacement makes sense when the glass has fogged or cracked, the frame is warped, the sash no longer closes tight, or the leak keeps coming back after a reflash. It also makes sense when the roof is close to replacement. Putting a new skylight into a roof that is about to be torn off means paying for the same flashing work twice.

A new unit also gets new flashing built for it, which removes the biggest weak point of an old installation. The roofer matches the opening, sets the curb and flashes the unit into the shingles in the right order, with the upper flashing overlapping the lower pieces so water runs off.

Roof replacement and the skylight

If the whole roof is worn, the skylight decision is part of a bigger one. Asphalt roof replacement in Northern Virginia typically runs $9,000 to $20,000, depending on roof size, pitch, layers to tear off and the shingle grade. A skylight that is replaced at the same time costs less in labor than one done separately, because the roofing crew is already working around the opening.

What to do before the call

Put a bucket under the drip and move anything valuable out of the way. Note whether the leak shows up in wind-driven rain or in any rain. Photograph the ceiling stain and the skylight frame from inside. Write down the brand on the glass edge if you can read it, since the roofer may need it to match flashing.

Then call the number on this site. The roofer checks the flashing, the seal and the shingles, tells you whether a reflash will hold, and gives the cost range for the job. Any permit rule is checked for the address with the City of Manassas or Prince William County, depending on where the house sits.