How far in advance should I book?
For a straightforward job with a standard sized unit, four to six weeks between agreeing the quote and the crew arriving is a fair expectation. For anything with a structural opening, a made to measure unit or a consent attached to it, plan on eight to twelve weeks and sometimes longer.
Those numbers are the sum of two separate waits that people tend to merge into one: the wait for the product to be manufactured and delivered, and the wait for a slot in the installation diary. They run partly in parallel, but they are governed by different things and it helps to think about them separately.
The two lead times that make up the wait
Product lead time is set by the manufacturer. A stock size roof window from a national brand is usually available within a week from a merchant. A made to measure flat rooflight is built to order, and four to eight weeks is normal. A large lantern with a special glass specification can be ten or more.
Diary lead time is set by the season and by the length of the job. A single day roof window slots into gaps easily. A three day lantern installation needs a clear run of settled weather and a crew, which is harder to place at short notice. The critical path is whichever of the two is longer, and for anything made to order it is almost always the product.
Grid sizes and bespoke units, and what each does to the lead time
This is the single biggest lever you have on the timeline. Roof window manufacturers work to a fixed size grid, and a unit on that grid is normally on a shelf somewhere in the region.
Flat rooflights are different. Most are made to the millimetre for the kerb they are landing on, which means nothing is ordered until the kerb is either built or precisely dimensioned. That sequencing is unavoidable, because ordering a bespoke unit off a drawing and then finding the kerb was built ten millimetres out is a very expensive way to save a fortnight.
Structural work, and the weeks it adds
Where an opening is wide enough to need a steel, a structural engineer produces a calculation before anything is ordered. That is typically one to two weeks from instruction to drawing, and it has to happen before the Building Control conversation is complete.
Steel fabrication adds another one to three weeks depending on the section and the fabricator. So a lantern needing a beam realistically sits at ten to fourteen weeks from first enquiry to a finished ceiling. The work itself is a handful of days. The paperwork and the fabrication account for nearly all of the elapsed time.
Consent, and the clock it starts
If the building is listed, or sits in a conservation area where permitted development rights have been removed by an Article 4 direction, an application has to be determined before the unit is ordered.
The statutory period is eight weeks, and twelve is realistic once a conservation officer has asked for a revision. That runs first, in series rather than in parallel, so a conservation job started in March is a June or July installation. Anyone planning work on a protected roof should start the consent conversation about four months ahead of when they want the crew on site.
Season, and the parts of the year that fill first
Spring and late summer are the busiest periods, for the obvious reason that people commission work when the weather looks reliable and when extensions are reaching the roof stage. March through June and September into October fill earliest.
January and February have more availability than people expect. Rooflight installation is not weather dependent in the way roof recovering is, because the opening is formed, weathered and closed within a single working day. The specific question of cold weather working is dealt with on the winter fitting page. Booking a February slot in November is often the shortest wait available all year.
Booking around an extension programme
On a new extension the rooflight is one trade among several, and the sequencing has two fixed points that matter far more than the booking date.
The first is design, when the size and position of the opening are agreed, because the builder forms the structure around them and that cannot be revised once the roof is up. The second is first fix, when a cable for an electric opener costs almost nothing to run and a great deal to add later. Get a survey booked as soon as the roof structure is up and the kerb is formed, and the unit can be ordered while the builder is still working.
Replacing a unit that has failed
A misted or tired unit does not always wait politely for a diary slot, and the timeline here depends entirely on the kerb.
A like for like replacement into an existing kerb, using a size that is on the grid, can often be done inside two to three weeks. A replacement where the old unit was an odd imperial size, which covers a great many of the domed units fitted across Essex in the seventies and eighties, needs a made to measure unit and returns to the four to eight week product lead time. Measuring the existing opening early is what tells you which of the two you are in.
A rough calendar, front to back
The table below assumes the survey happens promptly after the initial enquiry, which is normally the case.
| Job type | Enquiry to installation | What sets the pace |
|---|---|---|
| Roof window, standard size, pitched slope | 3 to 5 weeks | Diary availability |
| Flat rooflight, made to measure, existing kerb | 5 to 8 weeks | Manufacture |
| Sun tunnel through a loft | 3 to 4 weeks | Diary availability |
| Lantern on an existing flat roof, no steel | 6 to 10 weeks | Manufacture |
| Large opening needing a steel | 10 to 14 weeks | Engineer and fabrication |
| Conservation unit needing consent | 14 to 20 weeks | Determination period |
What you can do now to shorten it
Three things help more than anything else. Measure the existing opening or the intended one and photograph the roof from outside and the ceiling from inside, which is enough for a range by email straight away. Check the listing and the conservation area status before design work starts, because that is the longest pole in the tent. And decide early whether the unit opens and whether it is electric, since both are order decisions rather than site decisions.
Sunspire surveys, installs and handles the Building Control notification as part of the job across Chelmsford and thirty miles around it. The wider picture of how a rooflight installation is put together sits on rooflight and skylight installation in Chelmsford, and indicative ranges by job type are on the costs page.
Related questions
- Do rooflights need planning permission?
- Do I need building regulations approval for a rooflight?
- Who notifies building control about a rooflight?
- How much does a rooflight cost?
- Do rooflights add value to a house?
- Is a rooflight cheaper than a dormer?
Everything on skylight & rooflight installation & replacement chelmsford →
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