How to Fix A Leaking Skylight: A Complete Guide

Leaky skylights are one of those problems that seem minor – until they’re not. A drip here, a dark stain there, and suddenly you’re dealing with warped plasterboard, bubbling paint, or worse, a full-blown ceiling collapse. We’ve been helping customers upgrade their roof windows for over 15 years, and if there's one thing we've learned, it's this: skylight leaks don’t fix themselves.

Let’s walk through what might be causing the problem, how to pinpoint the source, and most importantly, how to stop it for good.

Common Causes of Skylight Leaks

Before grabbing the sealant, it’s worth understanding why skylights leak in the first place. It's not always the window's fault – often, the leak is coming from somewhere else entirely.

Poor installation

If your skylight wasn't fitted properly, water will find a way in. Fast.

Aging sealant

Over time, the seal around your skylight can crack or degrade.

Flashing issues

Flashing is the thin material installed to prevent water from entering at the joint. If it's damaged or missing, leaks are almost inevitable.

Roof damage nearby

Broken tiles or shingles around the skylight can redirect rainwater straight inside.

Condensation

Not technically a leak, but worth mentioning. Poor ventilation can lead to moisture build-up around the skylight, which mimics a leak.

How to Identify the Leak Source

You’d think spotting a leak would be simple, right? Unfortunately, water doesn’t travel in straight lines. It might sneak in at the top of your roof and pool around the skylight, tricking you into thinking that’s where the problem lies.

Here’s how to narrow it down:

Inspect during or just after rain

This gives you the best shot at seeing where water’s actually entering.

Use a hose

If you're confident (and safe), a garden hose can help simulate rainfall. Spray water gently over sections of the roof above the skylight while someone checks inside.

Check the seal

Is the silicone or rubber gasket around the skylight intact? Any cracks or gaps?

Look at the flashing

Flashing should sit flush with the roof. Any curling, lifting, or rust is a red flag.

Signs of a Leaking Roof Window

Sometimes it’s not obvious right away that the leak is skylight-related. Look out for:

Water stains

On the ceiling or walls near the window.

Peeling paint or bubbling plaster

Often an early indicator of prolonged moisture exposure.

Drips during or after heavy rain

If it’s active during weather events, that’s your confirmation.

Mould or mildew buildup

Especially around the window frame or nearby ceiling.

How to Fix a Leaking Skylight: Step-by-Step

Alright, you’ve found the leak (or at least narrowed it down). Here’s how to handle it:

1. Clean the area thoroughly

Remove any dirt, debris or moss from the skylight and surrounding roof area. You want a clean surface before applying anything.

2. Re-seal the perimeter

Use a high-quality exterior-grade sealant (think flexible and weatherproof). Apply around the edge where the skylight frame meets the roof, making sure you cover any visible gaps or cracks.

3. Check (or replace) the flashing

If the flashing is rusted, loose, or visibly damaged, it’s got to go. You can either attempt this yourself (if you're confident on the roof) or opt for a professional roofer.

4. Replace the skylight (only if necessary)

If the skylight itself is damaged, warped, or very old, replacement may be the most effective fix. Browse our high quality roof windows collection for options that are built to last.

5. Test your work

Once repaired, wait for the next rainy day – or repeat the hose trick – to ensure everything's watertight.

When to Call a Professional

We’ll be real: some skylight leaks are DIY-able. Others? Not so much. If any of the following apply, it’s time to bring in an expert:

You’re not confident working at height

No shame in staying on the ground.

The leak is coming from deep inside the roof

This likely means it’s not just the skylight at fault.

Multiple attempts haven’t worked

Persistent leaks can point to a larger issue.

You’re dealing with an older or non-standard window

These can be trickier to reseal or replace safely.

Our team is always happy to point you in the right direction, or help you source the parts you need. P.S.: We’ve also written a comprehensive guide to skylights if you’re exploring replacements or want to understand more about what’s available.

Final Thoughts

Leaks can be a pain – but with the right approach, they don’t have to be a disaster. Whether it’s a bit of resealing or a full replacement, tackling a leaky skylight quickly can save you money (and headaches) down the line.

Not sure where to start? Give our team a ring. We’re here Monday to Friday with real advice from real people – not scripts.

And if you’re ready to upgrade, explore our high quality roof windows collection to find something that suits your home, your budget, and your bright ideas.