A failed rooflight, or skylight in everyday speech, has a clear path from first call to finished roof, and most of the anxiety goes once you can see it laid out. This guide walks through replacing a failed rooflight in the order the work happens, from the survey on your roof to the handover, so you know what each visit is for and what you will be asked to decide.
What counts as a failed rooflight
The word covers several faults, and the fault decides the scope of the job. The commonest is a sealed glass unit that has lost its seal, so moisture sits between the panes and will not wipe off. The page on why rooflights mist between the panes explains how that happens. Others are a cracked pane, a dome that has crazed and yellowed, a frame that has distorted so the sash no longer closes, a rotten timber kerb, and flashings that have lifted so water finds its way in.
Some of these are a glass problem and some are a frame or kerb problem. That difference is the first thing the survey settles, because it determines whether the glass alone can be changed or the whole unit comes out. The guide on replacing the glass or the whole rooflight sets out how that call is made.
Whatever the fault, a failed sealed unit cannot be repaired in any lasting way. The gas fill and the seal are factory-made. Once the seal has gone, the honest route is assessment and then replacement.
Step one: the free survey
Every job begins with a free survey, and it is a booked visit, not a drive-by. Someone comes to the property, looks at the rooflight from inside and from the roof where it is safe to do so, and works out what has actually failed. They check the kerb or upstand for rot or movement, look at the flashings and the roof covering around the opening, and measure the opening itself.
Measuring matters more than people expect. A replacement has to suit the opening already there, or the opening has to be altered on purpose and made good. The surveyor records the clear size of the opening, the height and condition of the kerb, the roof pitch, the type of roof covering and what is below, because a rooflight over a stairwell is a different job from one over a kitchen extension.
Step two: the written quote and the access plan
After the survey you receive a fixed written quote. It names the unit, the work to the kerb or frame if there is any, the making good, and the Building Control route. It does not leave the price open until the roof is stripped. The page on what it costs to replace a misted rooflight explains what moves the figure, and the costs page covers the wider picture.
Inside that quote sits the access plan, a written page that says how we reach your roof. In Brighton & Hove that is often the hardest part of the job. Tall terraces, parapets, flat roofs behind mansards and converted flats with shared stairs all affect how a unit gets up and an old one gets down.
| Question | Typical answer | Who deals with it |
|---|---|---|
| How do we reach the roof | Rear scaffold, street tower or mobile platform | Us |
| Is a highway licence needed | Yes if scaffold stands on the pavement or road | Us, through the highway authority |
| Is a parking bay affected | Sometimes on narrow, permit-only streets | Us |
| Is freeholder consent needed | Often, in a converted building | You, with our paperwork |
| Which Building Control route | Local authority or a registered building control approver | Us, where notifiable |
Step three: choosing the replacement
A failed rooflight is a chance to fix whatever made it a poor fit in the first place. If the old unit was a single-glazed dome that dripped condensation all winter, the replacement can be a double-glazed or triple-glazed unit with a far better thermal performance. If the old one was too small or sat in the wrong place, that is the moment to say so, though changing the size of an opening is a bigger job than a like-for-like swap.
Plastic domes need their own treatment. The page on replacing an old plastic dome rooflight covers why they age and what goes in their place. If your rooflight is a glazed lantern, a flat glass unit, a pitched roof window or a VELUX, the replacement sits within the same family: see roof lanterns, flat roof rooflights, roof windows and VELUX windows.
Two regulation values frame the choice. For a pitched roof, the replacement roof window is held to 1.4 W/m²K, or Window Energy Rating band B, and a flat roof rooflight or lantern is held to 2.2 W/m²K. Both limits bite when the entire unit is renewed, which is why a like-for-like swap cannot simply copy an old, tired specification.
Step four: building control and the paperwork
When the failed unit comes out entirely and an equivalent goes in, that is building work: Building Control has to be notified and the new unit must satisfy Part L of the Building Regulations. Fitting new glass alone into a frame that is still sound is a different matter and not a controlled fitting, which is one reason the survey asks what exactly has failed. You can read more in the Building Regulations guide and in the page on whether replacing a rooflight needs Building Regulations approval.
The Building Control notice goes in from us, to the council or to a private registered building control approver depending on the job. You do not have to track down the right office or complete any forms.
Planning is a separate question. For a straight swap in the same opening, planning is rarely the issue, but listed buildings need listed building consent for alterations that affect character, and a flat has no permitted development rights at all. If you are unsure, the planning guide is the place to check, and many conservation areas in the city are covered by Article 4 directions from Brighton & Hove City Council, so confirm with the council before assuming anything.
Step five: scaffold, licences and neighbours
Most roof work in the city needs a safe working platform, and where that platform stands on the highway it needs a licence. We apply for the scaffold licence and for any parking bay suspension, since the paperwork comes from the highway authority and its timing has to match the job. How the process runs, without fees or lead times that change, is in scaffold licences and parking suspensions.
Some rooflights can be replaced from a platform or from inside the property. The page on replacing a rooflight without scaffolding covers when that is realistic and when it is not.
In a converted house or a block of flats, the freeholder generally owns the roof, and a leaseholder has to get written permission, known as a licence for alterations, so read your lease before accepting a quote. Rooflights in flats and leasehold buildings explains who to ask. The access plan also records the notice given to neighbours where their access or boundary is affected.
Step six: the day the old unit comes out
On the day, the order of work protects your home. The area below the rooflight is cleared and covered first. If there is a stairwell or a landing under it, the floor and the walls are sheeted. Then the roof side is prepared: surrounding covering is lifted back, flashings are released, and the fixings holding the old unit are cut or unscrewed.
The old unit is lifted out as a whole where it can be, which keeps broken glass away from your rooms. A failed sealed unit is heavier than it looks, particularly a large lantern or a flat unit with a deep frame. This is the part where the access plan earns its place, because a unit that cannot be carried down safely is a unit that cannot be removed safely.
Once the unit is out, the opening is inspected again. Kerb, upstand, trimmer and decking are checked now the frame is gone, because rot tends to hide under old frames. Any damaged timber is cut out and replaced before the new unit goes anywhere near the opening. This is also when the surrounding roof covering is judged: if it has been lifted back, it is dressed again so that water runs away from the joint and not into it.
Putting the new unit in follows the same order every time. It is set level, fixed to the prepared kerb or frame, and sealed into the weathering detail. Flashings are dressed last, so that the roof covering and the upstand work together as one watertight layer.
Step seven: fitting the new rooflight
Once the opening is clean and sound, the new unit is set in. On a flat roof that means a kerb with an insulated upstand and a weathering that ties into the roof membrane. On a pitched roof it means a flashing kit matched to the roof covering, whether slate, tile or something else. The detail at the head and the sill of the unit is where leaks start if it is wrong, so those are the junctions worth checking on completion.
Opening and electric units add a further step. Wiring, a rain sensor or a control panel have to be connected and tested. If you want to swap a fixed unit for an opening one, see electric and opening rooflights. If the main reason for replacing is heat loss or overheating, the energy efficient rooflights page is the better starting point.
Step eight: checks, clearing up and handover
Before the job is closed, the new unit is checked from both sides. Inside, the lining and any plaster or paint disturbed by the work is made good. Outside, the flashings, the fixings and the junctions are looked over, and anything that moves or opens is operated to confirm it works.
The site is cleared and the old unit is removed. If a scaffold stood on the highway, it comes down within the arrangement set out in the access plan. The Building Control notification is completed where the work is notifiable, and the finished roof comes with a 10-year workmanship guarantee. The guarantee page says what that covers.
If it is leaking right now
A rooflight that is letting water in is a stronger reason to book the survey sooner rather than later. In the meantime, a bucket and a towel at the drip, and keeping the area below clear, are sensible. Do not climb onto the roof to fix it yourself, and do not seal around the frame with a tube of mastic, because trapped water finds another route and hides the original fault from the survey.
The page on whether a misted rooflight is urgent helps you judge how quickly to act. Misting alone is usually a slow failure, while an active leak or a cracked pane is not.
How long a replacement takes to plan
The work on the roof is usually a short part of the whole process. The longer stretches are the order for the unit, which is often made to size, any freeholder consent, and the highway licence if scaffold is needed. For that reason, the best moment to start is before the winter, not once the stain has reached the ceiling.
We do not promise dates before the survey, because the survey is what tells us which of those stretches apply to you. The quote that follows states the scope, and the access plan states how the roof will be reached.
Next steps
If you have a misted or failed rooflight and want to know where you stand, the next step is a survey. It is free, it is booked, and it ends with a fixed written quote. Read the hub page on misted and failed rooflights in Brighton & Hove for the wider picture, or ask for a visit through the quote form.
