Yes, in most cases an old roof window can be swapped for a new one. The work involves the frame, the flashing and the lining, so a quick glass change is rarely the whole job.
Roof windows in Downend loft conversions and bungalow or dormer lofts often date from when the work was done, and they get tired. Replacing one is usually quite practical. It does mean looking at more than the window: the frame, the flashing kit and the lining around the opening all matter to whether the new one stays dry.
Why people replace them
The usual reasons are a window that leaks, misting between the panes from a failed sealed unit, a frame that no longer opens or closes properly, or simply wanting better insulation. Sometimes only the glazed unit has failed and can be replaced. At other times the whole frame, the flashing or the covering around it has worn out too. We check which applies before suggesting a route.
Finding a matching size
Where possible we replace like for like, using a window that fits the existing opening. That avoids touching the rafters and keeps the work simple. Where the old window is an unusual or discontinued size, or the opening was poorly formed, we may need to adjust the opening or choose a different size, and we explain what that involves. A like-for-like swap is also usually quicker and tidier inside.
Flashing, lining and the roof around it
A new window should be fitted with a flashing kit matched to the roof covering, so water is led off cleanly. Many leaks blamed on the window come from old flashings or tired tiles around it. Inside, the lining, insulation and vapour control are checked so condensation does not form. The usual steps are these: Old flashings that have lifted or cracked are a common hidden cause of damp.
- Old window and flashing removed carefully
- Opening and surrounding timbers checked
- New window set with the correct flashing kit
- Lining, insulation and sealing finished inside
- Roof covering dressed back and checked
Loft conversions and dormers
In a converted loft the finished ceiling and sloping walls leave less room to work. The reveal and plaster need care, and any damp found behind them is dealt with first. A dormer window may be a different type altogether. We look at what is actually in the roof before suggesting how it should be replaced. Bungalow and dormer lofts have their own quirks, which we sort out on site.
What to ask and what to expect
Ask which flashing kit will be used, whether the opening and lining will be checked, and how the roof is protected while open. Replacing a roof window may need planning or Building Regulations checks — we advise before work starts. Call us for a proper look at the window you have.
Frequently Asked Questions
Is it just the glass that needs changing?
Sometimes. If only the sealed unit has misted and the frame and flashing are sound, replacing the glazed unit may be enough. We check the whole window before telling you whether that is a sensible route. It depends on the frame.
Will replacing it disturb my ceiling?
Usually only the reveal around the window. Work happens from the roof and from inside the opening, so some care and dust sheets are needed. We explain how the lining will be finished before we start.
Can a new window be a different size?
Yes, but changing the size means altering the opening and possibly the rafters, which is a bigger job. A like-for-like swap is simpler, and we tell you what suits your roof. Both routes are possible.
Talk to our team about VELUX and roof window installation in Downend
Every roof is different — the fastest way to get an accurate answer is a quick chat with our team.