Skylights are one of those features that homeowners in London absolutely love — right up until they start leaking. Whether you have a Velux-style roof window in a Victorian terrace in Barnet, a flat roof lantern on a modern extension in Ealing, or a sun tunnel in a Harrow semi-detached, skylights need regular attention to perform at their best.
London’s climate doesn’t do skylights any favours. Between the autumn leaf fall, heavy winter rainfall, freeze-thaw cycles, and the occasional summer heatwave, your skylight seals, flashings, and glazing take a real battering throughout the year. The good news is that most skylight problems are entirely preventable with a simple seasonal maintenance routine.
This guide walks you through exactly what to look for, when to do it, and when to call in a professional roofer rather than risk making things worse.
Why Skylight Maintenance Matters in London
London properties — particularly Victorian, Edwardian, and inter-war homes across areas like Finchley, Golders Green, Camden, and Hampstead — often have ageing roof structures. Adding a skylight to an older roof is perfectly achievable, but it does create a penetration point in your weatherproofing. Over time, even a well-installed skylight can develop issues.
Left unattended, a poorly maintained skylight can lead to:
- Water ingress and damp patches on ceilings or walls
- Rotting timber rafters and roof decking
- Mould growth inside the home
- Increased heat loss in winter, pushing up energy bills
- Structural damage that costs far more to fix than the original maintenance would have
The key is to stay ahead of problems rather than react to them. A well-maintained skylight can last 20 to 30 years without significant issues. A neglected one can fail within a decade.
How Often Should You Maintain a Skylight?
As a general rule, skylight maintenance should be carried out twice a year — once in early spring to assess any winter damage, and again in early autumn before the wetter months set in. If you’ve experienced a storm, it’s worth doing a visual check immediately after.
For London homeowners near tree-lined streets — think Hampstead, Queen’s Park, Muswell Hill, or Dulwich — you may need to clear debris more frequently, as leaves and twigs accumulate quickly and block drainage channels.
Skylight Maintenance Checklist: What to Check and When
1. Clean the Glazing — Inside and Out
Dirty glazing isn’t just an aesthetic problem. Algae, moss, and grime buildup on the outer glass or polycarbonate panels can retain moisture and accelerate deterioration of the frame and seals. In London, airborne pollution accelerates this process more than in rural areas.
How to clean safely:
- Use a soft cloth or sponge with warm soapy water
- Avoid abrasive tools or harsh chemicals that can scratch the surface or damage seals
- For hard-to-reach skylights, use a telescopic window cleaning tool from ground level rather than accessing the roof yourself
- Never walk on a glass skylight panel — this is a serious safety risk
Clean the interior glazing at the same time. Condensation and dust buildup on the inside can obscure early signs of cracking or seal failure.
2. Inspect and Clear the Drainage Channels
Most skylight frames have small drainage channels or weep holes designed to guide away any water that gets past the outer seal. These can become blocked with debris, particularly in autumn.
Check these channels are clear and unobstructed. If water is pooling in the frame rather than draining away, that standing water will eventually find its way into your home.
For flat roof skylights, also check that the surrounding roof surface drains correctly. Poor drainage is one of the most common causes of skylight leaks on flat-roofed extensions across West London boroughs like Ealing, Acton, and Wembley.
3. Check the Flashing
The flashing is the metal (usually lead or aluminium) that seals the gap between your skylight frame and the surrounding roof covering. It’s one of the most critical components — and one of the most common failure points.
Signs of flashing problems include:
- Visible gaps or lifting at the edges
- Rust staining or corrosion
- Cracked or missing sealant around the perimeter
- Damp patches on the ceiling directly below or around the skylight
Lead flashing is the traditional choice and performs exceptionally well when properly installed. However, it can be prone to thermal movement, particularly on south-facing roofs that experience greater temperature swings. On London roofs, where Victorian lead work may be original or very old, replacement flashings can be a priority maintenance task.
If you spot flashing problems, it’s important to have them assessed by a professional. Poorly applied sealant as a DIY fix will fail quickly and can mask an underlying issue that gets progressively worse.
4. Inspect the Seals and Gaskets
Every skylight has rubber gaskets and sealant around the frame that prevent water from getting in. Over time, these degrade — they dry out, crack, and shrink, particularly after prolonged exposure to UV light and temperature extremes.
During your inspection, look for:
- Cracking or brittleness in the rubber gaskets
- Gaps or separation where the frame meets the roof
- Any discolouration or water staining around the frame interior
Seal replacement is generally a straightforward job for a competent roofer and is far more cost-effective than waiting until water ingress has caused timber damage.
5. Test the Opening Mechanism (If Applicable)
If your roof window opens for ventilation — common in loft conversions across North London — test the handle, hinges, and locking mechanism. A window that doesn’t close and seal properly is effectively a gap in your roof.
Lubricate hinges annually with a silicone-based lubricant. If the frame feels stiff or the seal is compressed unevenly, it may need adjustment or replacement hardware.
6. Check for Condensation and Moisture Between Panes
Double-glazed skylights can develop condensation between the panes when the hermetic seal fails. This appears as a permanent foggy or misty look inside the glazing unit. It won’t clear — it’s a sign the unit itself needs replacing.
This is particularly common in older Velux units or cheaper alternatives that may have been fitted during loft conversion projects in London’s housing stock.
When to Call a Professional Roofer
Some skylight maintenance tasks are safe and straightforward for homeowners to carry out from the inside or with a telescopic tool. However, you should always engage a professional roofer for:
- Any work that requires accessing the roof surface
- Flashing replacement or repairs
- Skylight resealing from the exterior
- Glazing unit replacement
- Any suspected structural issues around the skylight opening
It’s worth being cautious about rogue traders offering cheap skylight repairs, particularly after storms. Always ask for a written quote, check for insurance, and be wary of anyone who knocks at your door claiming to have spotted a problem from the street.
Seasonal Skylight Maintenance Summary
| Season | Priority Tasks |
|---|---|
| Spring | Full inspection after winter; clean glazing; check flashing & seals |
| Summer | Check for UV seal degradation; test ventilation mechanism |
| Autumn | Clear debris & drainage channels; inspect before wet season |
| Winter | Monitor for condensation & leaks; check after heavy rain or frost |
FAQs: Skylight Maintenance in London
How do I know if my skylight is leaking? The most common sign is a damp patch or water stain on the ceiling directly below or around the skylight frame. You may also notice peeling paint, condensation on interior surfaces, or a musty smell in the room.
Can I fix a leaking skylight myself? Minor interior cleaning and debris clearing is fine, but any work involving the roof surface, flashing, or exterior sealing should be carried out by a qualified roofer. Incorrect repairs can worsen the problem and void any product warranty.
How long does a skylight last? A quality skylight, properly installed and maintained, will typically last 20 to 30 years. Cheaper units or those in exposed London locations may need attention sooner.
What is the most common cause of skylight leaks in London? Failed flashing is by far the most common cause, followed by degraded seals and blocked drainage channels. London’s wet climate and older housing stock make these issues particularly prevalent.
Do I need planning permission to replace a skylight in London? In most cases, replacing a like-for-like skylight does not require planning permission. However, if your property is in a conservation area — common across Hampstead, Camden, and Barnet — or is a listed building, you should check with your local borough council first.
Keep Your Skylights Working Year-Round
Regular skylight maintenance is a small investment that pays back significantly in avoided repair costs, energy efficiency, and the longevity of your roof. For London homeowners, where the climate and ageing housing stock create extra challenges, twice-yearly checks are genuinely worth the effort.
If you’ve spotted a problem — or just want peace of mind before the winter rains arrive — the team at Smart Roofing London is here to help. We carry out skylight inspections, flashing repairs, and full skylight replacements across North and West London, including Barnet, Harrow, Finchley, Golders Green, Hampstead, Ealing, Camden, and the surrounding boroughs.
📞 Contact Smart Roofing London today for a free inspection and honest, transparent quote. No obligation, no hard sell — just expert advice from a trusted London roofing specialist.
