Can a rooflight be moved to a different part of the roof?

Two jobs, not one move

The mental model people arrive with is a window being unscrewed and refitted a metre away. On a roof, almost nothing transfers. The flashing kit is dressed to the courses it currently sits in and will not lift and re-lay. The trimmers are fixed to the rafters they were cut into. The reveal below has been plastered and painted to that position.

What travels is the unit itself, and sometimes not even that. So the sensible way to think about the cost is as a new installation plus a piece of remedial roofing, and to ask whether the value of the salvaged unit justifies the extra handling.

Whether the old unit is worth reusing

Check four things before assuming it comes with you:

• Age. A unit past fifteen years is likely to have hinges, gaskets and a glazing unit at or near the end of their working lives. Refitting it buys a short future.
• The seal on the glazing. Misting between the panes means the sealed unit has already failed, and the frame is then the only thing worth moving.
• Thermal performance. A new opening is notifiable work and has to meet the current standard. An older unit may not, which settles the question on its own.
• Condition of the frame. Timber frames that have been under a poorly detailed perimeter often have soft corners that only show once the unit is out.

Where the unit is recent, sound and adequately specified, reusing it is reasonable and we will price it that way. Where it is not, the honest position is that a new unit costs less than the labour of nursing an old one into a new opening.

Closing the old opening properly

This is the part that gets underestimated. Done correctly it means new rafter sections spliced in or new common rafters fixed alongside so the slope is continuous again, the trimmers removed or left in place as appropriate, battens replaced at the original gauge, underlay pieced in with laps running the right way, and the covering reinstated.

The covering is the visible risk. New tiles or slates in the middle of a weathered slope announce themselves for years. The way round it is the same as anywhere else: take material from a hidden area of the roof to fill the visible one, and put the new material where nobody sees it.

Structural closing up and area re-covering sit outside our scope. We install and replace rooflights, and we are deliberately narrow about it. Where a move is what you want, we will price our half and tell you plainly what the other half involves so you can put a roofer or a carpenter alongside us rather than discovering the gap afterwards.

The ceiling and the reveal below

Inside, two areas of ceiling are in play. The old reveal comes out entirely and the ceiling is reinstated flat, insulated to the same standard as the rest, boarded, skimmed and decorated. The new position needs a reveal formed and splayed.

Decoration is where this bites. A made-good area of ceiling almost never disappears into an existing painted surface, so the realistic scope is redecorating the whole ceiling, and often the whole room where the walls are involved. Worth budgeting for at the outset rather than being surprised by.

What constrains where the new one can go

The new position is subject to every constraint a first installation faces, and people who have lived with a rooflight for years sometimes assume the roof will simply accept another one anywhere. It will not.

Rafter spacing caps the width unless a rafter is cut. The head needs enough covering below the ridge to lap into. The foot needs to stay clear of the eaves and any purlin. A chimney nearby imposes clearance. A valley rules the position out entirely. Pitch has to be within the published range for the unit. Any one of those can move the new opening a course or two from where you pictured it.

Permission is judged on the new position, not the old

An existing rooflight gives you no rights over a new one. The new opening is assessed on its own merits and its own location.

That matters most where the unit is moving from a rear slope to a front one, or from a hidden slope to one visible from a highway. Permitted development rights limit how far a rooflight may project and generally exclude the plane of the roof slope facing the highway. Conservation areas, Article 4 directions and listed buildings each change the position further. Our pages on permitted development limits and front elevation rooflights cover where the lines fall.

When moving is worth it, and when it is not

Moving genuinely pays where the existing unit is in the wrong place for the room: over a stairwell instead of the living space, badly off-centre in a converted loft, or throwing light onto a wall rather than into the room.

It rarely pays where the motive is a modest improvement in view or position. In that case the better arithmetic is usually to leave the existing unit alone and add a second one where you want the light, since the access is the same, nothing has to be closed up, and you end up with more daylight rather than the same amount relocated. Where the existing unit is tired, replacing it in place and adding a new one in the better position is often the strongest use of a single visit.

Sequence, and how long the roof is open

Access goes up first and serves both openings. On the day, the new opening is formed, weathered and closed before the old one is touched, so the roof is never left in a state where two areas are open at once.

Each opening is opened and closed within the same day. The roof is not left open overnight and it is not covered with a sheet and left to the weather. Where the closing up is being done by a roofer working alongside us, that sequencing is agreed before anybody starts rather than negotiated on site.

Fifteen years installing and replacing rooflights around Oxford, the Building Control notification handled for the new opening, a range by email and a fixed price after the survey, and ten years of guarantee on our workmanship. Call 01865 704245 or email info@heritageskylightsoxford.co.uk.