How long does a rooflight installation take?
One day outside and one day inside, for a straightforward roof window going into a single rafter bay on an accessible slope. Day one is the covering back, the opening formed and trimmed, the unit set and flashed, and the covering re-laid. Day two is insulation, the reveal, plasterboard and skim. That is the base case, and it holds for a good proportion of the work on Gloucestershire’s tiled and slated roofs. What lengthens it is structural work, a difficult covering, difficult access, or the number of units, and each of those adds a predictable amount rather than an unknown one. The calendar is a separate question from the days on site, and the two get confused more often than anything else in the process. The job itself is described on the roof window installation page.
Hour by hour through the first day
The crew arrives to scaffold or a tower already standing, because it goes up ahead of the fitting day. Inside, floors and furniture are covered and the loft hatch is sealed before anything is cut. The setting-out is marked from inside the room, then transferred outside by drilling through at the corners.
The covering comes off next, stripped back further than the opening on all four sides and stacked for re-use rather than dropped. Battens are cut back, the underlay is opened, and the opening is formed. Trimmers go in, the frame is set, packed square and fixed, and then the weathering: the underlay dressed up over the head and out to the bays either side, the apron at the cill, the soakers or side flashings interleaved course by course, the head flashing dressed under the course above. The covering is re-laid into the flashings and the cut tiles at the sides are mechanically fixed. On a single unit in an accessible slope, that is a full day and it finishes with the roof whole.
Five o’clock, with the roof closed before anyone leaves
The sequence exists to serve one rule: the roof is never left open overnight. An opening is not started unless it can be closed and made watertight the same day. If the forecast turns during the morning, the outside work stops at a point where the covering is continuous, and the opening waits for the next dry day.
That governs how a bigger job is planned rather than the other way round. Where several units are going in, the sequence runs from the top of the slope downwards so that every evening ends with a closed roof and nothing above the finished work is still open. It is the reason a four-unit job is planned as four sequenced days rather than one long strip-out, and it is worth knowing that the timetable is built around it.
The second day: insulation, reveal and plaster
Inside, the work is joinery and finishing. Insulation is taken tight and continuous around all four sides of the frame with no voids, and the vapour control layer is taped to the frame rather than trimmed short of it. The reveal is then framed: a vertical lining above the head, a horizontal lining below the cill, and the two sides splayed where the room benefits from it.
Plasterboard follows, then beads, then a skim coat. That is a day for a single unit. The finish then has to dry, and that is calendar time rather than site time: a skimmed reveal wants somewhere between three days and a week before it takes mist coat and paint, longer in a cold room in January than in a warm one in June.
Cotswold stone slate, where the covering sets the timetable
On a stone slate roof through Painswick, Bibury, Northleach or Chipping Campden, the covering stops being a day’s work and becomes most of the job. The slates diminish in size up the slope and every course has its own gauge, so the courses above the opening have to be taken back up the slope, the frame set, and the courses re-laid downwards re-establishing the original gauge.
Slates come out broken. Reclaimed stone is sourced to match thickness and weathering colour, and that sourcing happens well before the fitting date rather than on the day. Add the weight, the steep pitch and the fact that everything has to be handed down rather than stacked, and a conservation rooflight into a Cotswold roof is commonly a three to four day job outside where a concrete tile semi would be one. The scope of that work is set out on the conservation rooflight installation page.
Structural work, and the day a designed trimmer adds
An opening in a single bay adds nothing to the timetable. An opening across two or three bays does, because rafters are cut, the slope is propped while they are out, and a heavier trimmer goes in. That is usually half a day to a day of extra work on site, plus a Building Control inspection at the right moment.
Removing a truss on a modern estate at Quedgeley or Bishops Cleeve is a bigger step. It means temporary support, a beam spanning to the trusses either side, hangers, and an inspection before anything is covered up. Two days is a realistic figure for the structural element alone, and the engineer’s calculation and the approval both have to be in hand before the covering comes off. None of that is unusual. It just needs planning as a longer job from the start.
Access, and the Stroud valleys
Getting to the roof can add more time than the roof itself. A two-storey rear slope with a driveway to park on and a garden to build scaffold in is the easy case. A Stroud valley terrace at Chalford or Rodborough, one storey at the front and three at the back, reached by a shared footpath and a flight of steps, is not.
Scaffold that has to be hand-carried in takes a day or more each way rather than a morning. Where a lorry cannot get within fifty metres, the unit and the glass need extra hands or a mechanical lift. That is priced from the survey with the access looked at properly, so the figure and the timetable both hold. The same applies to a third-storey slope on a Cheltenham terrace, where the lift height changes what the scaffold has to be.
Weather, and the mornings the outside work does not start
Rain does not stop a job, it postpones the outside half of one. Stripping covering in steady rain puts water into a roof void that then has to dry, so the sensible call is to move the day. Wind is the harder limit: a large pane on a scaffold in a gusting wind is a genuine hazard, and lifting stops well before the wind speed becomes dramatic.
Cold matters for the finishing rather than the roofing. Lead work and flashings are fine in winter. Plaster in an unheated loft in January dries slowly, and mortar bedding on a ridge does not want a hard frost overnight. Through a Gloucestershire winter the honest planning assumption is that a two-day job may run across three or four calendar days, and that is built into the date rather than discovered.
Several units on one scaffold, and why the total is not a multiple
| Job | Days on site | What dominates |
|---|---|---|
| One roof window, single bay, concrete tile, accessible | 2 | The base case: one day outside, one inside |
| Two units in adjacent bays, same slope | 3 | One set-up, two openings, one longer internal day |
| Four units, loft conversion, cut roof | 5 to 6 | Sequencing from the top of the slope down |
| One unit with a designed trimmer over two bays | 3 | Propping, the trimmer, and an inspection |
| Conservation unit into Cotswold stone slate | 4 to 5 | Taking back and re-laying diminishing courses |
| One unit, Stroud valley terrace, hand-carried scaffold | 2 on the roof, plus access days | Getting material to the elevation |
The pattern is clear enough: the second unit on the same scaffold costs far less time than the first, because the set-up, the strip-out and the internal finishing all overlap. Where a roof has three or four units of the same age, doing them together is materially quicker as well as cheaper than doing them one at a time.
From first email to a finished room
The calendar runs longer than the site days and it is worth seeing it laid out. An indicative range comes back by email within a day or two of photographs arriving. A survey follows at a time that suits, taking about forty minutes for a single roof window. The fixed price comes after that.
Then lead times. Standard manufactured roof windows in common size codes are usually available within a week or two; a specific finish, a triple-glazed unit or an electric one can run to four to six weeks; reclaimed stone slate takes as long as it takes to find. The Building Control notification goes in during that period, scaffold is booked, and the fitting dates are set against the delivery rather than against hope. From first contact to a decorated room, four to eight weeks is a normal span for a straightforward job, most of it waiting rather than working.
Next on this subject.
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