Skylight Leaking? It's Almost Always the Flashing

When someone calls about a leaking skylight, they almost always think the skylight is faulty. Nine times out of ten, it isn’t. The unit’s fine — it’s the flashing around it that’s letting go. That’s the metal collar that ties the skylight into the roof, and it’s where these jobs are won or lost.

Why skylights leak

A skylight is a hole you’ve deliberately cut in the roof. The only thing keeping water out is how well that hole was sealed back up. Get the flashing right and it’ll outlast the rest of the roof. Get it wrong and no amount of silicone will save it.

The usual culprits we find:

• Silicone instead of proper flashing. Someone’s relied on a bead of sealant rather than folded metal. Silicone perishes, cracks, and then it’s a leak.
• The wrong flashing kit — or none at all. Velux make specific flashing kits for the roof type they’re going into. Use the wrong one and water tracks underneath.
• Bad detailing where the roof meets the skylight on the high side, where water has to be diverted around the unit.
• An old unit at end of life — sometimes it genuinely is the seals, but that’s the minority.

Tile vs metal

Worth knowing: we install and re-flash Velux skylights into both metal and tile roofs. For tile we use the proper Velux EDW flashing kit, reset the tiles around it and make it weather-tight. (To be clear — we don’t do full tile roof replacements; that’s not our trade. But cutting in and flashing a skylight to a tile roof, we do.)

On metal roofs, the best time to add a skylight is during a re-roof — the flashings go in flush and there’s no retrofit compromise. But we retrofit into existing roofs all the time too.

How we fix it

We don’t patch and hope. We find where the water’s actually getting in (not always where it shows up inside — water travels), strip the bad flashing, and re-flash it properly with the right kit, custom-folded where it needs to be. Then we test it. The goal is a fix you don’t think about again, not a callback in three months.

Get it looked at

If you’ve got a stain spreading on the ceiling under a skylight, don’t wait for it to get worse — water in the roof cavity does damage you can’t see. Heasly & Son are licensed roof plumbers (Vic 108555), Velux installers, 15 years on Melbourne roofs and fully insured. Send us a photo and the building details and we’ll come and sort it.