Surrey Skylight Curb Leaks: Causes, Signs and Fixes
Surrey Skylight Curb Leaks: Causes, Signs and Fixes
A skylight that leaks around its curb almost never needs a tube of sealant. It needs the flashing, the curb and the roof membrane or shingles around it to be rebuilt as one watertight system. In Surrey’s long wet season, that means a proper inspection of the curb, the corners and the waterproofing layers underneath, followed by a repair that fixes the cause. We do that work on Surrey homes, townhouse complexes and commercial roofs, and this guide shows you what to look for first.
TL;DR
- The curb is the raised frame the skylight sits on. Most “skylight leaks” are really curb flashing, corner or membrane failures, not a bad window.
- Surrey’s steady rain, moss and temperature swings work on the weakest detail: the corners and the uphill side of the curb.
- Surface caulking buys weeks, not years. A lasting fix means reflashing the curb and tying it into the roof.
- Hail can crack or dent a skylight dome or frame. Photograph it and have the roof checked before the next rainfall.
- Stains on the ceiling are late news. Book an inspection when you see the first brown ring, not the first drip.
Table of Contents
- What a skylight curb is, and why it leaks
- Why Surrey is hard on skylight curbs
- Reading the signs before the ceiling tells you
- Why caulking over the problem fails
- What a proper curb repair involves
- Surrey skylight hail damage
- Strata, townhouse and commercial roofs
- A simple yearly routine for homeowners
- Perspective: why we reflash instead of reseal
- Get your skylight curb looked at
- FAQ
- Sources
What a skylight curb is, and why it leaks
A curb is a small box, usually framed in wood, that rises above the roof deck. The skylight unit sits on top of it. Roofing material runs up the sides of the curb, and metal flashing covers the joint so water that runs down the roof is steered around the box instead of into it.
That is a lot of seams in a small space. A typical curb has four corners, four sides, a roof-to-curb joint on each side and a skylight-to-curb joint on top. Water that runs down the roof meets the uphill side of the curb head on. Everything below that side has to carry the water around to the downhill side without letting it behind the metal.
When a leak shows up, it is usually one of these:
- Corner failure. Corners are where flashing is folded or cut, and where sealant is most likely to crack. A pinhole at a corner can let in a surprising amount of water in a heavy storm.
- Uphill-side failure. Debris, needles and moss collect behind the curb. Water pools, backs up under the flashing and finds a way in.
- Membrane or shingle termination. The roofing has to run up the curb and be sealed or lapped correctly. If the top edge of the membrane has lifted, water slips behind it.
- Old sealant doing the flashing’s job. Sealant is meant to be a backup. When it is the only barrier, it fails as soon as it ages or the roof moves.
- Condensation mistaken for a leak. Moisture forming on cold glass or the frame can drip like a roof leak. If your drips come on cool mornings with no rain, read our guide on skylight condensation in Surrey.
Why Surrey is hard on skylight curbs
Surrey sits in the wet part of the Lower Mainland. Rain arrives for months at a time, and it often comes with wind from the southwest. Wind-driven rain does not just fall on a roof, it pushes sideways, into the vertical faces of curbs and up under flashing laps. You can see how much rain your area typically gets in the Environment Canada climate normals, which publishes long-term averages by weather station.
Three local conditions make curbs work harder than on a dry-climate roof:
- Constant wetness. A curb that stays damp for weeks gives moss, algae and rot a place to start. Wood framing that is wet on the outside and warm on the inside is slow to dry.
- Moss and debris. Shaded roofs under Douglas firs and cedars collect needles and leaves. These pile against the uphill side of a curb like a small dam.
- Temperature swings. Cold snaps followed by mild, wet weather make metal and sealant expand and contract. Over many winters, that movement opens up hairline gaps at corners.
Many Surrey houses and townhouses were built with skylights that were flashed to the standard of the day. After 15 to 25 years the flashing, the sealant and the roofing around it have all aged together. That is why a skylight that was fine for a decade can suddenly leak in two or three places at once.
Reading the signs before the ceiling tells you
You do not need to climb on the roof, and you should not. A wet, mossy roof is slippery, and skylights are exactly where people fall. From inside and from the ground you can pick up most of the early signals.
Inside the house
- A faint brown or yellow ring on the drywall around the light shaft
- Paint that bubbles or peels at the top corners of the shaft
- A musty smell in the room below after a few days of rain
- Drips that only appear in wind-driven rain, which points to the sides and corners of the curb
- Drips during any rain, which points to the uphill side or a failed membrane termination
From the ground or a window
- Moss or a heap of debris on the uphill side of the skylight
- Sealant that looks cracked, stringy or smeared on top of flashing
- Flashing that has lifted or sits at an odd angle
- Shingles or membrane near the skylight that are curling or sagging
A useful habit is to note when the drip happens. A leak that only shows during the wind and rain of a storm, and a leak that shows after two days of gentle rain, usually have different causes. Tell the inspector. It shortens the search.
Why caulking over the problem fails
Every homeowner reaches for the tube first, and it is understandable. A bead of sealant around the curb looks like a quick, thrifty move. The trouble is that it hides the symptom and traps water.
Sealant sits on top of flashing. If water is already getting behind the flashing, the new bead seals the exit as well as the entrance. The water then travels further into the curb framing or the roof deck, and the visible leak may stop for a few weeks while rot spreads. By the time the stain returns, the repair is bigger.
Sealant also does not fix the shape of the problem. If debris is damming water against the curb, if the membrane has lifted, or if the flashing was never lapped in the right order, the leak will come back wherever the new bead ages first.
What a proper curb repair involves
How much work the curb needs depends on what the inspection finds. In general, the repair moves in this order.
1. Find the real entry point
Water can travel along rafters, sheathing and the light shaft before it appears on the ceiling. The spot where it shows up is rarely the spot where it came in. A careful inspection checks the flashing, corners, curb face, roofing terminations and the skylight unit itself, and rules out condensation. If you have a leak and don’t know where it starts, our leak detection and repair page explains how we approach it.
2. Check the curb and deck underneath
Before anything new goes on, the wood must be checked. A soft curb or damp roof deck cannot hold new flashing. Damaged framing is replaced so the new flashing has something solid to attach to. Skipping this step is the most common reason a repair fails within a couple of winters.
3. Reflash in the right order
Flashing works like shingles on a small scale: each piece overlaps the one below it so water always moves outward. The lower side goes on first, the sides next, and the uphill side last, so water running down the roof passes over the top of every joint and not into it. On low-slope roofs, the membrane is carried up the curb and finished under a counter-flashing, so there is no exposed edge facing the weather.
4. Tie into the roof covering
On an asphalt shingle roof, shingles are woven around the flashing and sealed only where the manufacturer allows. On a flat or low-slope roof with EPDM or torch-on membrane, seams around the curb are the most exposed part of the roof and need careful detailing at corners. Whatever the roof, the repair has to match the roofing, not fight it.
5. Add a way for water to leave
On the uphill side of a wide curb, a small diverter, sometimes called a cricket, can send water around the curb instead of letting it pool. It is a small detail that matters on larger skylights.
6. Clean and test
Moss, needles and debris are cleared from the area, and the finished work is checked. If the skylight itself is old or the seal in the glass has failed, replacement of the unit may be the better call than another repair. Our skylight repair and installation page for Surrey covers both.
Surrey skylight hail damage
Hail is not an everyday event on the Lower Mainland, but when it does fall, skylights are the first thing on the roof to show it. Plastic domes can crack or pit. Glass units can chip at the edge. Aluminum or copper frames and flashing can dent, and a dent at a seam can open a path for water.
What to do after a hailstorm:
- Stay off the roof. Look from the ground, from an upstairs window or with binoculars.
- Photograph everything you can see, with the date, including ceiling and light shaft conditions inside.
- Check the ceiling the next time it rains for new drips or stains.
- Contact your insurer if you see damage, and keep your photos and any inspection report for the claim.
- Book a roof inspection. Hail damage to a curb or flashing is easy to miss from the ground, and water damage that follows can be larger than the hail damage itself.
If the skylight is actively leaking, our emergency roof repairs can make the roof watertight until a full repair is scheduled.
Strata, townhouse and commercial roofs
If you manage a townhouse complex, a strata building or a commercial property, skylight curbs deserve a line in your roof maintenance plan. A building with a dozen skylights has a dozen small points of failure, and a slow leak under one can reach insulation, drywall and units below long before anyone files a report.
Practical steps for property managers and strata councils:
- Keep a skylight list. Note the location, age and any past repairs for each unit.
- Inspect on a schedule , and again after major storms, especially before the wet season.
- Clear debris from uphill sides as part of routine roof maintenance.
- Group repairs. If several skylights are the same age and style, reflashing them in one visit usually makes more sense than repairing them one leak at a time.
- Record each repair. Dates and photos help depreciation reports and insurance claims.
We work on strata and multifamily roofs as well as commercial buildings. See our strata and multifamily roofing services and commercial roofing services for what we do for those properties.
A simple yearly routine for homeowners
You can do a lot from the ground and the inside of your house:
- Look at each skylight shaft ceiling once in the fall and once in late winter.
- Take a photo of any stain, then compare it a month later. A ring that grows is an active leak.
- Note whether moss is building near the skylight. Our guide on how to clean moss off a roof in BC explains why moss matters, and our moss removal and treatment service handles it for you.
- Have a roofer look at the flashing every few years, and sooner if the roof is more than 15 years old.
Perspective: why we reflash instead of reseal
We get calls every wet season from Surrey homeowners who have already put a bead of sealant around their skylight, sometimes two or three. They are frustrated, and they should not be. A curb looks simple from below, and it is easy to assume a tube will solve it.
Our approach is to treat the curb as part of the whole roof. We look at the flashing, the corners, the roofing that ties into the curb and the framing underneath, because a leak can start in one place and show up in another. We are licensed and insured, and our focus is on solving the specific problems that Surrey and Metro Vancouver weather create.
If we can repair the curb properly, we will. If the skylight itself is at the end of its life, we will tell you, and we can replace it. Either way, the goal is a dry ceiling for years, not a quick patch that hides the issue until next winter.
Harman
Get your skylight curb looked at
If you have a stain, a drip or a skylight that has taken a hit from hail, we can inspect it and tell you what is going on. We handle skylight repair and installation in Surrey, along with residential roof inspections and repairs for homes, and we serve strata corporations, property managers and commercial owners as well. Start with our Surrey skylight repair and installation page, or see our residential roofing services.
If water is coming in now, call us about emergency roof repairs so the roof is protected before the next storm.
FAQ
Why does my skylight only leak in heavy wind and rain?
Wind-driven rain pushes water sideways and upward into laps and corners that normally shed water downward. A leak that appears only in storms often points to a flashing corner or a lap on the windward side of the curb. An inspection of those spots usually finds it.
Can I fix a leaking skylight curb with roofing sealant?
Sealant can slow a leak for a short while, but it sits on top of the flashing and does not fix the reason water gets in. It can also trap water behind the metal. A lasting repair reflashes the curb and ties it into the surrounding roofing.
How do I tell a skylight leak from condensation?
Condensation forms on cold glass or the frame, usually on cool mornings, and often without any rain. A leak shows up during or after rain and tends to leave stains on the drywall. If you are unsure, an inspection can tell the two apart, and our skylight condensation guide covers the fixes.
What should I do if hail damaged my skylight?
Stay off the roof, photograph the damage from the ground and inside, and check the ceiling the next time it rains. Contact your insurer and have the roof inspected, since dented flashing or a cracked dome can let water in even when the leak is not yet visible.
Should I repair or replace an old skylight?
If the curb and flashing are the problem and the skylight unit is sound, reflashing is usually enough. If the glass seal has failed, the frame is damaged or the unit is very old, replacing it while the curb is rebuilt often makes more sense. An inspection will show which applies.
Sources
Recommended
Our Roofing Blog
Have more questions about roofing?
Check out our FAQs or give us a call today to speak to an expert roofer in Vancouver Lower Mainland, BC. We're here to help our neighbours make educated decisions about their roof. For our team, we value helping clients save money while making their roofs last.
