Replacement answer
Can a VELUX be swapped into the same opening?
Often you can. A window of the same footprint drops into the hole the old one leaves, as long as the roof around it is sound and nothing about the job has changed.
The answer
Usually yes. A new window with the same size code as the old one fits the opening already there, and the flashing, collars and lining are renewed with it. The swap stops being simple if you want a different size, if the rafters or covering around the opening are unsound, or if the house is listed. Those cases are checked at the free survey before a price is fixed.
Will a window of the same size code fit?
Yes, when the code matches. The new frame takes the old frame's place, and the opening stays as it is. The parts around it are changed.
A size code is a footprint. Two windows with the same code are made to sit in the same opening, which is why a like-for-like replacement is the easier route. If you are unsure of yours, see the VELUX size codes guide.
What the swap involves
The old sash and frame come out. The flashing is lifted, the collar underneath is taken away and the lining inside is cleared. The new frame goes in, with a fresh flashing kit to suit the covering, a new underlay collar, an insulation collar and a new lining. Slates or tiles round the edge are re-laid.
Why the old flashing is not reused
Flashing is shaped to the frame it was made for, and once bent back and refitted it seldom lies as it did. A new frame deserves a new kit, and the join is the part of the job that keeps the weather out.
Same size does not mean same specification
The new window will usually have better glazing than one fitted years ago. For an existing dwelling in England, the limiting U-value for a roof window is 1.4 W/m²K, or WER Band B, so the replacement must meet that.
What comes out with the window?
The flashing, the collars, the lining and the blind fittings, usually. Those parts are made for the frame, so they go when the frame goes.
People often expect the window to be the only thing replaced. In practice it is a package.
Flashing and collars
The outside metalwork and the underlay and insulation collars are all matched to the frame. They are replaced as a set.
The inside
The lining is the angled surface of board or plaster that runs from the window to the ceiling and walls. A new frame may sit at a slightly different depth, so the lining is usually renewed and decorated. Any blind or control bracket fixed to the old frame is also affected. A new blind may be chosen to suit the new unit.
The covering around it
Slates and tiles are lifted and relaid, and a few will be cracked in the process. Spares from elsewhere on the roof, or matched replacements, fill the gap. Our guide to flashings for slate and tile explains why the covering is part of the job.
Use the list to see what to check before the survey.
Before the swap, look at these
- Whatever the label says, or a note that it has disappeared.
- Staining or soft plaster around the lining inside.
- Any slipped or cracked slates and tiles near the window.
- Whether a blind or control is fixed to the old frame.
- Who owns the roof, if the house is a flat.
Is a like-for-like swap a planning matter?
Putting a window back into its existing opening is a different matter from adding a rooflight. Check any change in size or projection, and read your lease if it is a flat.
The planning rules for rooflights are written for new rooflights. A window put back into the opening of the old one, with the same footprint and standing no higher above the roof, is not the same as adding another.
Where the answer shifts
If the new window is larger, or stands further off the roof slope, you have changed the opening or its height. On a house, Class C of permitted development covers a rooflight that projects no more than 150mm beyond the plane of the roof slope and sits no higher than the highest part of the roof. A new rooflight in a flat must go through planning with the council. Our rooflight planning guide sets out both. A listed house needs listed building consent for almost any rooflight work, and that consent decides the job.
Building Control
Where the work is notifiable, we handle the Building Control notification, whether to the local authority or a registered building control approver.
The panel shows who decides in each kind of home.
Which house is yours?
Upstairs flat
- Who decides
- You and the other owner, as set by the title or lease. Check it, and speak to them, before ordering.
- Which rules apply
- A swap that changes size or height is a new rooflight, and a flat has no householder permitted development.
Downstairs flat
- Who decides
- You, though the roof may belong to the building as a whole. The lease or title names who has to agree.
- Which rules apply
- The same flat rules apply: a changed window needs planning permission, and an unchanged one is checked at survey.
House
- Who decides
- You, as the owner. If the house is listed, listed building consent applies as well.
- Which rules apply
- Class C covers a like-for-like swap within 150mm of the slope unless an Article 4 direction or condition removes it.
When does the opening have to change?
When the size changes, or the rafters or covering around the old opening are not sound. Then it becomes a new opening, with the rules that come with one.
Sometimes the survey finds that the hole is the problem.
A different size
A bigger window needs roof timbers cut and trimmed. A smaller one means closing up part of the old opening. In both cases the job is a new opening in a roof, which is building work notified to Building Control.
A tired opening
If timbers around the old window have been wet for a long time, they may need replacing before a new frame goes in. The survey looks for soft or stained wood and notes it in the quote, so there are no surprises on the day.
A different type
Changing from a top-hung to a centre-pivot style may shift the fixing points. The pivot versus top-hung comparison explains the difference. See the VELUX windows hub for the whole range of jobs we handle.
Swap questions from the loft
Do I need a new frame as well as new glass?
Sometimes only the glazing has misted and the frame is sound. Fitting just new glass, or a new unit, is weighed up on its own page.
Can a different make go in a VELUX opening?
It can, though the footprints will not match exactly. A swap of make usually means adjusting the opening slightly and fitting the new maker's own flashing. The survey measures it before anything is ordered.
Will the plaster inside need redoing?
The lining is normally renewed with the window, and the decoration around it made good. If the plaster is damp or soft, the survey flags it before the quote is fixed.
How do I know what the survey will find?
It is a free survey of the window, the covering and the roof timbers, followed by a fixed written quote. You can book one through the quote page.