A cracked pane in a roof window looks worse than most other glass damage, mainly because you’re staring straight up at it every time you walk into the room. The good news is that a crack or even a full breakage rarely means the whole window needs replacing. It does mean understanding what you’re actually looking at, since a hairline crack in the outer pane and a shattered inner pane call for very different responses.
Why Velux Glass Doesn’t Shatter Like a Normal Window
Roof windows take a battering that a wall window never sees: hailstones, falling branches, birds, and the occasional dropped tool during unrelated roof work nearby. Because of that, Velux glazing has been toughened and, on most models made in the last couple of decades, laminated as standard on at least one pane. Toughened glass is designed to break into small, blunt fragments rather than long shards if it does fail, and laminated glass has a plastic interlayer that holds the pieces together even when cracked, which is why you’ll sometimes see a Velux window that’s clearly cracked right across but hasn’t actually fallen apart or let rain through yet.
This matters for safety glazing standards too. Roof windows fall under building regulations that require safety glazing in overhead and low-level glazed areas, precisely because a normal annealed pane breaking overhead would be genuinely dangerous. If you’ve got an older Velux window from before these standards tightened, that’s worth knowing before you replace it, since the new unit will need to meet current standards even if the original didn’t.
What a Crack Actually Tells You
A crack confined to the outer pane, with the inner pane still clear and intact, usually means the window is still keeping weather out for now, but it won’t stay that way indefinitely. Moisture can work its way into the crack over time, and once it reaches the seal around the sealed glazing unit, you’re looking at a failed unit and condensation between the panes on top of the original crack.
A crack or shatter on the inner pane, the one facing into the room, is more urgent, particularly if there’s any chance of glass falling into the room below. Even with lamination holding things together, a badly cracked inner pane needs sorting quickly rather than left to see how it goes.
Either way, once any pane in a double or triple glazed unit is damaged, the whole sealed unit typically needs replacing rather than swapping out just the damaged pane on its own, since the panes are bonded together with a specific spacer bar and gas fill that can’t easily be separated and rebuilt.
How Velux Sources Replacement Panes for Older Models
This is where people often assume they’re stuck, particularly with a window that’s twenty-plus years old. In practice, Velux keeps a genuinely long back catalogue of glazing specifications, and even discontinued window models generally have a current equivalent glazing unit that fits the original frame, even if the glass makeup itself (thickness, coating, gas fill) has moved on since the window was first fitted. It’s one of the reasons Velux windows have such a good reputation for being repairable rather than needing full replacement the moment something goes wrong, something we cover in more depth in our guide to Velux window repairs and maintenance.
The one thing worth flagging before you get a quote: a replacement glazing unit for a genuinely old model sometimes needs ordering in specifically rather than being available same-day, since it isn’t stock that gets held for every size and specification indefinitely. That’s a few extra days’ wait, not a sign the window can’t be fixed.
Reglazing vs Full Window Replacement: What Actually Changes the Cost
Reglazing, replacing the sealed glass unit while keeping the existing frame, is the cheaper option in the great majority of cases, and it’s what we’d recommend whenever the frame itself is sound. You’re paying for the glazing unit and the labour to fit it, not a whole new window, new flashing kit, and the disruption of a full re-fit.
A full window replacement becomes the better value option when the damage isn’t limited to the glass, for example if the frame has also warped, rotted, or the hinges are failing alongside the cracked pane, or if you were already planning to upgrade the window (moving to electric or solar operation, or a larger size) and the glass damage has simply brought the decision forward. Trying to reglaze a frame that’s on its way out anyway just means paying for the glass now and the frame later, usually at a higher combined cost than doing both together would have been.
As a rough rule, if a reglaze quote comes in above roughly half the cost of a full replacement for that same window size, it’s worth getting a replacement quote alongside it before deciding, since the gap can be smaller than people expect once you’re paying for access and labour either way.
There’s one more factor worth weighing before booking a Velux window repair for cracked glass alone: how many other jobs you’re likely to need doing on the same window over the next few years. A window with a single cracked pane and nothing else wrong is a straightforward reglaze. A window that’s already had a hinge replaced, has a slightly stiff opening mechanism, or is coming up on the age where flashing typically starts to fail is a different calculation, since booking one access visit to deal with several issues together is nearly always cheaper than paying for a roof ladder or tower scaffold on separate occasions for each fault as it appears.
Frequently Asked Questions
Can I board up a cracked Velux window myself in the meantime?
For a genuinely urgent situation, such as a shattered pane letting weather straight in, a temporary cover is reasonable until someone can get out to assess it properly. It’s not a fix, and working at height on a roof pitch isn’t something to attempt without the right access equipment.
Is a cracked Velux window covered under guarantee?
Accidental damage from an impact, a falling branch, hailstones, and similar, isn’t typically covered under Velux’s 10 year product guarantee, since that covers manufacturing faults rather than external damage. It’s always worth checking the specific cause with whoever assesses it, since a crack that started from a manufacturing defect is a different conversation.
How long does it take to get replacement glazing for an older Velux window?
Standard sizes and specifications are often available within a few days. Genuinely old or unusual sizes can take a little longer if the unit needs ordering in specifically, but it’s rare for a Velux window to be beyond sourcing replacement glass altogether.
Will a cracked pane get worse over time?
Generally yes, particularly once moisture gets into the crack. What starts as a purely cosmetic issue can turn into a failed seal and condensation between the panes if it’s left long enough, so it’s worth getting looked at even if the window still seems to be keeping the weather out for now.