01The short version
How long a skylight fitting takes
It depends on what is going in and what is coming out, so here are honest ranges rather than one tidy number.
People ask how long it takes to fit a skylight because they want to know how long the house will be disrupted. Fair question. The answer is that a like-for-like swap is quick, a brand new opening is slower, and a large lantern is a small building project in its own right.
As a rule of thumb, a straightforward roof window or flat rooflight swap is typically done within a day. A new opening in a tiled or slated roof usually takes longer, because the roof has to be opened up, the structure framed around the gap and the covering made good. A lantern on a flat roof extension takes longer again. Timings always depend on access, the roof type, the size of the unit and the conditions on the day, and we confirm them on the written quote after a free survey.
| Job | Typical on-site time | What stretches it |
|---|---|---|
| Roof window swapped for the same size | Within a day | Awkward access, rotten timber found |
| Flat rooflight swapped on an existing kerb | Within a day | Kerb needs rebuilding |
| New roof window in a pitched roof | One to three days | Rafter changes, plastering |
| New flat rooflight in a new opening | Two to four days | Structure, kerb build, finishes |
| Roof lantern | Several days to a week or more | Size, lifting, lining |
02Swaps
Why a swap is the quick one
When the hole already exists, most of the hard work has been done by whoever built the roof.
Replacing an old roof window or flat rooflight with a new one of the same size means the opening, the surrounding structure and often the lining are already there. The old unit comes out, the frame and surrounding roof layers are checked, the new unit goes in and is tied into the roof covering or kerb. Then we clear up.
Our team lays floor protection first and covers furniture, because the working area is in your living space, not on the roof alone. The lining stays untouched where it can. That is a big reason these jobs are quick: nothing needs plastering afterwards.
The usual snag is what lies under the old unit. Rotten timber round an old frame, or a flat roof upstand that has crumbled, adds time. We tell you about it as soon as it is found and agree the next step before carrying on. If you are weighing up a swap, our guide to replacing an old rooflight follows the day through step by step.
- Floors and furniture covered, access set up
- Old unit and flashings taken out
- Frame, kerb and surrounding timber checked
- New unit fitted and joined to the roof covering
- Inside tidied, rubbish removed, Building Control notified where required
03New openings
What adds days to a new opening
Cutting a hole where none existed means structure, then roof covering, then the inside finish, and each takes its own time.
A new opening starts with the roof structure. In a pitched roof, one or more rafters are cut and a trimmer, a short beam that takes the load, is fixed across the gap. In a flat roof, joists are framed round the opening, and then a kerb or upstand is built on top. That is a raised collar the rooflight sits on, and for warmth it is insulated and joined to the roof insulation. Only then does the glazing go on.
Then there is the lining inside, the plasterboard reveal. Plaster is wet, so it needs drying time before paint goes on, and a day or more is common before a plastered reveal is ready to decorate. That drying is the main reason a new opening can feel slower than the actual fitting.
Rooflights that are wide or heavy can also need lifting kit, which has to be arranged for a particular day. Lanterns are the clearest case. A lantern arrives as a built frame with glass, and getting it onto the roof, levelling it and sealing it to the upstand is slow, careful work.
04Before the day
What happens before anyone is on the roof
The fitting day is short because the paperwork, the measuring and the ordering have been done already.
Everything starts with a free survey and written quote from Radiant Skylights. We look at the roof, measure the opening or the room, and talk through the glazing and the kerb. Then comes the order. A standard roof window can be quick to obtain. A made-to-measure flat rooflight or a lantern is made to your sizes, so lead times can run to several weeks and depend on the maker. That wait can be the longest part of the whole job, and it is worth asking about when you book.
Part L of the Building Regulations makes a full swap of rooflight, frame and glass a controlled fitting. When a job falls under that, the Building Control notification is ours to deal with. Our page on whether rooflights need Building Regulations explains where the line falls. A new opening may also need planning permission checked first, which our planning guide covers.
- Clear the space under the opening and the route to it
- Move small valuables and anything fragile out of the room
- Tell us about pets, working from home and access limits
- Ask for a realistic start window, since the roof needs a dry day
- Agree the decorating plan if plaster is involved
Days, dust and disruption during a skylight fit
Can a skylight be fitted in one day?
A like-for-like roof window or flat rooflight swap often can be, provided access is straightforward and nothing unexpected turns up under the old unit. New openings and lanterns typically take longer.
Will I be without a roof at any point?
The roof is opened only as far as the job needs and closed again with temporary cover if the work spans more than one day. We plan the order of work around the forecast. Our page on fitting skylights in winter goes into that.
How long until I can decorate?
Where plaster has been used, it needs to dry before it is painted, and the time depends on thickness and how warm and ventilated the room is. Where the lining was untouched, you can carry on straight away.
Does a bigger rooflight take much longer than a small one?
Size matters most for weight and lifting. A larger unit needs more hands or kit, a stronger opening and more careful sealing. A big flat rooflight is a longer day than a small one, and a lantern is longer again. See our roof lantern page for what that involves.
