leaking Velux skylight

Why do skylights leak?

Skylight leaks are one of the most common type of leaks on a roof.

There are many reasons why skylights are vulnerable to leaks. Some causes are quite obvious and some are harder to pin down…


First hand experience:
I have a large skylight in my home and it is installed on a terracotta tiled roof. It provides good natural light and for many years, it stayed dry during the heaviest of storms. Then one day when it was raining quite heavily, water was pouring down the ceiling at the side of the skylight…

I do not do emergency repairs in the rain – but in this instance, I made an exception to the rule. It was tricky on the wet tiles even after I waited for the rain to die down to a drizzle before attempting a fix.

I unseated the roof tiles from the side of the skylight and got a real appreciation of the role that leaves and dirt can play in blocking the flow of water on a skylight underflashing. Leaves and debris had built up over time and had were jammed against the underside of the roof tile where it rested on the flashing. This caused a ‘damming effect’ – and diverted the flow of water over the lip of the flashing into the ceiling cavity.

It was a simple matter then of removing the debris and the skylight has been fine ever since.

So, if you get a sudden downpour from the side of your skylight, then it will be leaves causing the problem. Sometimes, the skylight leak suddenly stops again as the rain continues to fall. This indicates that the leaves have been dislodged by the water flow and is no longer an obstruction.

This can be a source of frustration on the poor roofer who gets called out to investigate the skylight leak and find that everything looks ok – simply because the obstruction had cleared itself and there was no evidence left behind.
The video below shows exactly how the leaves can cause the obstruction:


A persistent seepage from the skylight surrounds.

A small (but persistent) leak at a skylight usually means a faulty skylight, a faulty skylight installation – or a minor blockage.

Often the soaker flashing on the base of the skylight has deteriorated (usually happens to the lead flashing at the downstream end of traditional dome skylights and Velux skylights)

Tray flashings Vs soaker flashings

soaker flashing at skylight
The Traditional skylight soaker flashing

The traditional soaker flashings that many roofers use when they cut a skylight into a roof (picture above) has no long term durability. The sealants fall apart or the soaker flashings rust because of ponding.

Different levels of trusted roof repairer
Tray flashings are more ‘fool-proof’

The best long term solution is to install a ‘tray’ flashing around the skylight (on the picture above). A tray flashing eliminates the tricky connection area on the upstream edge of the skylight and provides a superior long term flashing solution.


Jack the Roofer

Jack Yuen

Jack Yuen (Jack the Roofer) started roofing work in 1999 and have built a career in "roof repair expertise" on Sydney roofs. Jack is a leading voice on how roofs should build, maintained and repaired to provide the best outcomes for both roofers and property owners

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8 years ago

Hi i need flashing replaced around my skylight..front part.

Pat lacey
Pat lacey
7 years ago

My skylight is not leeking the surrounds are rusting and I needtp replace it and need to clean the mildew of it. It is fairly old not cracked . It is about 600 x 900 approx. How much to replace if needed.

5 years ago

My skylight is fine during rain. But a few days after the rain, during which there aren’t any rain, all of a sudden there is a downpour of water from the skylight.

Would debris have been the cause?


Kind regards,


chris jarrett
chris jarrett
2 years ago

Do you do works in the Hawkesbury?
I have a skylight that leaks under heavy rain . I have been up and looked no debris noticeable