Skylights · Service

Skylight repair starts with what is actually leaking

Water around a skylight comes from four different places and only one of them is the skylight. Getting that right is the whole job — the wrong diagnosis here is how people end up buying a new unit that leaks in exactly the same spot.

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In short

What is skylight repair?

Almost all skylight repair is leak repair, and the first job is deciding which of four things is at fault: the flashing around the unit, the seal at the glazing edge, the roof covering upslope of the skylight, or condensation forming inside the light shaft. They look identical from the ceiling and they are four different repairs at four different prices. A competent repair starts on the roof and in the attic, not with a quote.

Triggers

Signs you need skylight repair

A stain or a drip at the ceiling opening that appears during or shortly after rain, and dries out between storms
Water running down the inside face of the glass, or beading along the bottom edge, in cold weather with no rain at all — the classic condensation signature
Moisture, cloudiness or a mineral film trapped between the panes that will not clean off from either side
Staining at the top of the light shaft only, which usually means water is arriving from the roof above and running down to the opening
A venting unit that will not close fully, will not seal when closed, or whose motor or crank has stopped responding
Cracked or lifting sealant around the frame, especially where somebody has already repaired it with caulk

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The job

How skylight repair actually works

Separate condensation from water ingress before anything else

The question that decides the whole job: does it happen when it rains, or when it is cold? Water on the inside face of the glass in cold weather, with no correlation to rainfall, is household moisture condensing on the coldest surface in the room. The fix is ventilation, humidity and shaft air sealing — not roofing.

Watch for: Any contractor who quotes for reflashing without asking when it happens. It is the first question, and if it is not asked you are paying for roof work to solve a humidity problem.
Trace the water on the roof and from inside the attic

Where there is real ingress, it is traced from above and below — checking the head flashing and the courses above it, the step flashing up the sides, the sill, the curb if there is one, and the deck around the opening from the attic side, where staining shows the true entry point rather than the exit point.

Watch for: A diagnosis made from the ceiling stain alone. Water enters high and travels down rafters and along the shaft before it appears, so the visible mark is frequently nowhere near the hole.
Repair the flashing properly, or reflash completely

Where the flashing is the fault, the honest repair is usually to strip it back and install a complete new manufacturer kit for the unit and the covering, rather than to patch a piece. Partial repairs to interleaved flashing rarely hold, because the failure is normally the sequence rather than one component.

Watch for: A repair delivered as a bead of sealant around the frame. Sealant has a service life of a few years against flashing's decades — it is a deferral, and it makes the eventual proper repair harder because the old material has to come off first.
Deal with the glazing seal, or accept that it is a replacement

Moisture trapped between the panes of a sealed glazing unit means the seal has gone. That is not repairable in place on most residential skylights; the glazing unit or the whole skylight is replaced. The exterior gasket where the glass meets the frame is a different component and can often be renewed.

Watch for: Being told a failed sealed unit can be "dried out" or drilled and vented. It restores neither the appearance nor the insulating performance you paid for.
Dry, repair and finish the inside

Anything wet inside the shaft — insulation especially — is removed rather than covered. Wet insulation in a closed cavity does not dry, and the staining and smell return. Then the drywall, trim and paint are made good.

Watch for: New drywall going over insulation that is still damp. Ask to see the cavity before it is closed up, or ask for a photograph.

Money

What does skylight repair cost?

Small repairs — resealing a gasket, freeing an operator, clearing a blocked weep channel — are commonly a short call-out. A full reflash sits well above that, and a failed sealed glazing unit generally means replacing the skylight. See the skylight cost guide for current ranges.

See the full skylight repair cost guide — by material, size and region →

Straight answer

When skylight repair is the wrong call

Everyone else ranking for this is paid when you say yes. Here's when you shouldn't.

The moisture only ever appears in cold weather. That is condensation, and no amount of roof work will fix it. What will: extracting bathroom and kitchen moisture properly, air sealing the shaft, and in some rooms simply running the humidity lower in winter.
The glass has moisture between the panes. The sealed unit has failed and there is no repair for it — anyone quoting a repair for this is either misdiagnosing or selling you a delay. Price it as a replacement.
Your roof is due for replacement inside a couple of years. Anything beyond a holding repair is money you will tear off. Get it watertight, and put the full reflash or the new unit into the roofing scope.
It has already been reflashed correctly and still leaks. The fault is upslope on the roof, not at the skylight, and repairing the skylight again will not change anything. This needs a roofer looking at the covering above it.
What has failed is a blind, a motor or a remote. That is an accessory or parts issue with the manufacturer, not a roofing repair, and going through the manufacturer or a dealer is usually far cheaper than a roofing call-out.

Straight answer

Can I do this myself?

Do not go up to investigate a skylight leak on a wet, steep or high roof. Falls are what actually injure people doing this, and the pull to go and look is strongest in exactly the conditions that make it most dangerous — during or right after the rain that revealed the leak.

Reasonable to DIY

Recording when it happens: during rain, after rain, or only in cold weather. This one observation is more useful than anything else you can give a contractor.
Checking from inside the attic with a torch, on a dry day, for staining above and around the opening
Running the bathroom or kitchen extraction properly and seeing whether the problem disappears — a free test that resolves a good share of these

Call a licensed pro

Any repair to the flashing. It interleaves with the roof covering in a set order, and the commonest DIY outcome is a sealed-over leak that reappears once the sealant ages.
Anything on a tile, slate, metal or low-slope membrane roof, where walking on it incorrectly causes more damage than the leak.
A leak you cannot correlate with rain or with cold. That usually means it is arriving from upslope and it needs someone who can read the roof.

Before you sign

What to check when hiring for skylight repair

Did it start with rain, or with cold weather?

Ask this of yourself before you call anyone, and expect the contractor to ask it too. If they do not, they are not diagnosing — and condensation is a large share of reported skylight leaks.
Will you inspect from the attic as well as from the roof?

The entry point is usually higher than the stain. The attic side is where staining on the deck shows where the water is really coming in.
Have you checked the roof covering above the skylight?

The skylight interrupts water flowing down the slope, so a failure upslope shows up at the skylight. Missing this is why some units get reflashed twice.
Is this a patch or a complete reflash, and what is the difference in price and expected life?

Both can be legitimate — a patch to get through to a roof replacement, a full reflash otherwise. What you want is to be told which one you are buying.
Is there wet insulation in the shaft, and will you remove it?

Wet insulation sealed inside a cavity does not dry, and it comes back as staining and smell. This is the part most likely to be skipped because nobody sees it.
What warranty comes with the repair itself?

Leak repairs are where warranties are vaguest. A specific written term on the workmanship tells you how confident they are in the diagnosis.

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Related work

Often done at the same time

Skylight Replacement

When repair is no longer the answer

Skylight Installation

Adding a new one, and doing it right

Solar Powered Skylight

Venting out the moisture

Roof Repair

When the water is arriving from upslope

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FAQ

Skylight Repair — questions people ask

Still have a question? Talk to our team →

Why does my skylight leak only sometimes?

The pattern is the clue. Wind-driven rain from one direction only usually points at side or head flashing; a leak in heavy rain but not light rain often means water is backing up behind a blocked or badly detailed head flashing; and a leak in cold weather with no rain at all is not a leak — it is condensation on the coldest surface in the room. Record which conditions produce it before anyone quotes.

Can a leaking skylight be repaired, or does it have to be replaced?

Most can be repaired, because most skylight leaks are flashing failures rather than unit failures and the flashing can be replaced with the unit staying in place. The exceptions are a failed sealed glazing unit — moisture between the panes, which is not repairable — and old plastic domes that have become brittle. Repairing a unit that is at the end of its life is a false economy when the roof has to be opened either way.

How much of a skylight leak is actually condensation?

Enough that it should always be ruled out first. A skylight is one of the coldest surfaces in a room, so household moisture from cooking, showering and drying laundry condenses there before anywhere else. The distinguishing features are that it happens in cold weather rather than in rain, it appears on the glass itself rather than at the edges of the shaft, and it improves when you ventilate the room.

My skylight leaks even though it was reflashed. What now?

Look upslope. A skylight interrupts water running down the roof, so anything failing above it — a cracked tile, lifted or missing shingles, a poor valley, a nail that has backed out — sends water to the skylight, where it becomes visible. If the flashing has genuinely been done properly and the leak persists, the next inspection should be of the roof covering above the unit rather than of the skylight again.