How Long Do Skylights Last?

Why there is no single figure

Ask how long a skylight lasts and you will be given a range by anyone honest, because the answer depends on the type, the glass, the position of the roof and the standard of the fit. We would rather say what actually wears than quote a number that cannot be backed up. What follows is the order in which things tend to go.

What ages first

The parts of a skylight and how they wear

Sealed glass unit	The edge seal can eventually fail and let moisture between the panes
Seals and gaskets	Rubber and sealant harden with sun and weather
Flashings and upstand details	Wear depends on how they were dressed in and what they sit against
Frame	Timber needs its finish kept up, while aluminium and coated frames are slower to change
Opening mechanism	Hinges and motors wear with use

Frames and glass are usually in good shape long after the seals have started to show their age. A skylight that is misting between the panes is telling you about its unit, not about the whole rooflight, and there is more on that in replacing an old skylight.

A good fit and a good product both count

A well made rooflight set badly will not last. The long-term enemies are water getting past a poorly dressed flashing and a frame that is not properly supported. The hidden work, trimmers, upstands, flashings, membranes and insulation, determines how a rooflight ages. That is why we do it carefully and photograph it for you at handover, and why our 10-year workmanship guarantee covers the fitting.

What makes a skylight last longer

A rooflight in a sheltered position ages differently from one that takes the full brunt of weather, and one on a south-facing slope sees more sun than one facing north. Neither is a reason to expect trouble, but both affect how the seals age.

Signs it is nearing replacement

Misting between the panes is the commonest sign, followed by a frame that no longer closes tightly, stained plaster around the opening, or an opening mechanism that sticks. A single sign does not always mean a whole new rooflight, and a fit that was done properly can often take a new glass unit alone. When the frame, glass and flashings are all tired, replacement of the whole rooflight makes more sense, and that is notifiable work, and the rules for that are set out on the page about Building Regulations approval for skylights.

Weather, aspect and the York climate

Rain, frost and sun each wear a rooflight in a different way. Repeated freezing and thawing works on sealant joints and on any water that has found its way into a gap. Strong sun hardens rubber gaskets and fades some frame finishes, so a south-facing slope often shows age sooner than a north-facing one. Trees overhead add leaf litter and bird droppings, which sit against flashings and hold damp against them. None of this is dramatic, but a glance at the outside of the window once a year, from a ladder or from a window below, catches most problems while they are small.

Inside, look for a tide mark on the lining, a cold edge along the frame or a faint whiff of damp. These show up long before water drips.

Older does not always mean worse

Many older rooflights were well made, and a long-lived one may simply need new seals. Newer glazing, though, performs better on heat loss, and a new unit can improve how a room feels. If a skylight is working properly, there is no reason to replace it for the sake of its age.

Choosing for the long term

If you are choosing a new skylight, a few details help it age well. A frame finish that suits the roof, laminated inner glass over a room, and good seals all matter more than a headline feature. Keep the maker's maintenance advice with your paperwork. For a flat rooflight, look at how high the upstand stands above the roof. Insulated upstands of at least 150mm keep water clear of the frame, which protects it for longer.

On a pitched roof the covering around the window matters just as much, and it should be in good enough condition to be worth flashing into. If the slates or tiles around the opening are near the end of their own life, mention it at the survey so the two jobs can be planned together.

Warranties and what they cover

The maker gives a warranty on the product, and we give a workmanship guarantee on the fit. The two cover different things, and at handover you receive both, with the product details. The Prestige Skylights York home page explains how the survey and quote work if you would like an older rooflight looked at before you decide.