How long does a rooflight installation take?
One day for a roof window in a pitched slope. One to two days for a flat rooflight into an existing flat roof. Two to four days for a roof lantern, depending on whether there is a steel in it. Those are the figures for the fitting itself, and they are reliable. What people underestimate is everything either side of the fitting: the lead time before anyone arrives, the scaffold going up and coming down, and the plastering and decoration afterwards. The whole programme from first email to a finished reveal is usually six to ten weeks.
This page breaks that down. The detail of what happens hour by hour on a pitched slope sits on roof window installation.
The fitting durations, by unit type
The type of unit and the roof it is going into set the duration more than the size does.
| Job | Fitting time | What moves it |
|---|---|---|
| Roof window, existing pitched slope | One day | Slate cutting, awkward access |
| Two roof windows, same slope | One to two days | Combination flashing, covering type |
| Flat rooflight into an existing roof | One to two days | Kerb build, covering to be made good |
| Like for like replacement into an existing opening | One day | Whether the flashing is renewed |
| Roof lantern, timber trimmed opening | Two to three days | Kerb, glazing bars, panel handling |
| Roof lantern with a structural steel | Three to four days | Steel delivery, propping, bearings |
Those are working days on site, not calendar days, and they exclude the plastering that follows.
What fills a one day fit
A single roof window in a tiled slope is a full day for two people, and there is very little slack in it. The morning goes on protection, setting out the opening from inside against the actual timbers, stripping the covering back beyond the opening on all four sides, and trimming.
The afternoon is the frame set level and square with the diagonals checked, the underlay dressed and the head drainage formed, the flashing kit fitted, and the covering re-laid and cut in around the frame. The insulation collar and the vapour apron go on from inside before anyone leaves. The roof is closed and watertight at the end of the day whatever the forecast has decided to do.
Why a flat rooflight often runs to two
A flat unit into an existing flat roof has an extra stage that a roof window does not: a kerb has to be built and the covering has to be made good around it.
Day one is usually stripping back, opening the deck, trimming the joists and constructing the kerb, with the opening made temporarily weatherproof at the end of it. Day two is the covering dressed up the kerb, terminated, and the unit set and sealed. Where the covering is GRP or mastic asphalt, the curing or cooling time is real and it dictates the sequence rather than the other way round. Single ply is quicker because it is welded and immediately finished.
Where the time goes on a lantern
A lantern is the longest of the common jobs and the time is not in the glass. Forming the structural opening, building and insulating the kerb to a true level and a true rectangle, and dressing the covering up it takes the first two days on most installations.
The lantern itself then assembles in half a day to a day, ridge bar and rafters first, then the glazed panels worked in order. Where a steel is involved, add propping, the steel delivery and lifting it into position, and the bearings being formed and packed. That is the version that runs to four days, and it is worth knowing before the project is planned rather than after.
The lead time before anyone arrives
This is the longest single element of the programme and it is almost entirely manufacturing.
A standard roof window in a common size with a standard flashing kit is usually available within one to two weeks. A non-standard size, a specific glazing specification or a conservation frame runs to four to six weeks. A made to order lantern or a large flat rooflight is typically six to eight weeks from order, because the frame is fabricated and the sealed units are made to the drawing. Ordering happens after the survey, since the survey is what confirms the structural opening, so the clock starts there.
Scaffold, and the days either side
Where access needs scaffold, that adds days at both ends that have nothing to do with the rooflight. A domestic scaffold to a rear slope typically goes up in half a day, and it comes down in half a day, but the booking is the issue rather than the erection.
Scaffold is scheduled around the fitting with a margin on each side, so a one day fit can occupy a scaffold for a week. Where the structure stands on a public footway, as it does for a front slope on a Victorian terrace in central Chelmsford or Colchester, a highway licence is needed and the local authority’s notice period governs the date. Whether scaffold is required at all is set out on scaffolding for a rooflight.
Weather, and what actually stops work
Less than people expect. A roof is opened and closed within a working day, so a forecast of showers is worked around rather than worked in. Rain during the fitting itself is managed with temporary covering, and the opening is never left uncovered while it is happening.
What genuinely stops work is wind. Handling a large glazed panel or a full sheet of underlay on a roof in a strong gust is not sensible at any height, and there is a point at which a day is called off rather than pushed through. Persistent heavy rain also delays GRP, which needs a dry substrate to cure onto. Frost affects mortar bedding at ridges and verges. Across an Essex winter that usually means one or two days lost across a longer project.
Plastering and decoration, and the wait between coats
The internal reveal is where the programme quietly extends. Once the frame is in, the opening is lined with plasterboard, the reveal splayed at the head and returned vertically at the sill, and then it is skimmed.
Fresh plaster wants to dry before it is painted, and on a reveal that is typically four to seven days depending on the time of year and the ventilation in the room. Painting too early traps moisture and the finish suffers for it. So a window fitted on a Tuesday is plastered on the Wednesday and painted the following week. That gap is normal and it is worth planning around rather than being surprised by.
The whole programme, first email to finished reveal
Put end to end, a straightforward roof window runs roughly like this. A range comes back by email within a couple of days of the first photographs. The survey is booked within a week or two, and the fixed written figure follows it. The unit is ordered on acceptance and arrives in one to two weeks for a standard size. The fitting takes a day. The plaster goes on the following day and is painted a week later.
That is six to eight weeks in total for a common job, and ten to fourteen for a lantern with a steel and a scaffold. The Building Control notification runs alongside and is handled as part of the job, so the completion certificate follows without anything further being asked of the householder. Sunspire fits new rooflights and replaces units that have reached the end of their working life.
Tell us about your roof
We start with the building, the covering and the slope. Then we tell you what will suit it, and what it will cost, as a fixed written number.
- Surveyed before it is priced
- 10-year workmanship guarantee
- Building Control notification handled
- New installations and replacements