Typical time on site, by type of skylight
How long skylight installation takes depends mostly on what kind of rooflight it is and whether the roof already has an opening. The figures below are general ranges for a single unit in an ordinary house, not a promise for any particular roof.
A pitched roof window, a flat rooflight and a lantern are different jobs. The first sits in the rafters and is weathered with a flashing kit into the tiles or slates. The second sits on an upstand or kerb in a flat roof and is sealed into the membrane. The third is a framed glazed structure, assembled on site, that can span several metres. Our guide to types of rooflight explains what each one is for; the table here is only about time.
| Type | Typical time on site | What sets the pace |
|---|---|---|
| Sun tunnel | Half a day to 1 day | Tube route through the loft |
| Pitched roof window | 1 to 2 days | Rafters and inside lining |
| Flat rooflight | 1 to 2 days | Kerb and roof covering |
| Roof lantern | 2 to 4 days | Size, kerb and assembly |
These are working days with trades on site. A second unit of the same type in the same room typically adds hours rather than a full extra day, because the access, dust protection and tools are already in place. Conservation rooflights and walk-on units sit within the same ranges as their pitched and flat cousins, although their heavier frames and closer detailing can push them towards the top of the range.
Why a pitched roof skylight is usually a one-day job
A roof window going into a tiled or slated slope is quick when the frame fits between two rafters. The roof can be opened, weathered and made watertight in a morning, and the rest of the day goes on the inside.
The sequence is steady: dust sheets down, the ceiling cut, insulation lifted back, then the roof covering opened from above. The frame is fixed, the underlay collar and flashing are built up around it, and the tiles are relaid. Inside, the reveal is insulated, a vapour control collar goes on, and new lining boards are fitted and skimmed. That inside work is what typically fills the afternoon. If the window is wider than the gap between rafters, one rafter is cut and trimmed with new timbers, which is structural work and is more likely to take the job into a second day. Slate and small plain tiles, common on Victorian terraces off Mill Road and in Romsey, take longer to cut in and relay than large concrete interlocking tiles. The roof window installation page covers range and glass in more depth.
Flat rooflights and lanterns take longer on the roof
On a flat roof, the time goes into the kerb and the waterproofing rather than the glass. The unit itself can go on in under an hour; building what it sits on is the real work.
A new flat roof rooflight needs an opening cut through the deck, the joists trimmed around it, an upstand built to the height the manufacturer specifies, and the roof covering dressed up the upstand and sealed. Felt, single-ply membrane, GRP and liquid-applied roofs each have their own method and curing time, which is why a flat rooflight typically runs from one to two days. A roof lantern adds assembly: the ridge, hips and glazing bars go together on the kerb, the glass units are lifted in and bedded, and the capping and trims are fitted. A lantern of a metre or so can be done in two days; a long lantern over a kitchen extension, with heavy glass that needs several people or lifting equipment, is more likely to take three or four. Where the lantern goes onto a brand-new extension, the builder usually prepares the kerb first, which moves some of that time earlier in the build.
The weeks before and after the fitting days
The days on site are the short part of the project. The survey, any approvals and the product's delivery set the calendar, and decorating comes afterwards.
- Survey and light plan. A light survey takes about an hour in your home. The written quote and light plan that follow set out the position, size, glass and shading, and the reason for each.
- Approvals. Many rooflights on houses fall under permitted development, but conservation areas, listed buildings and flats need checking first. Our guides to planning permission for rooflights and Building Regulations for rooflights explain when an application or a notification is needed. Where the work is notifiable, we handle the Building Control notification, and it runs alongside ordering rather than after it.
- Product lead time. This varies by product and by maker. Standard sizes of pitched roof windows are often available at short notice, while made-to-measure flat rooflights, lanterns and conservation units are manufactured to order and can take several weeks. The quote should state the expected lead time for the specific unit, and it is worth confirming it before you book other trades around it.
- Drying and decorating. Fresh plaster around a lining needs to dry before it is painted. How long depends on the thickness of the skim, the ventilation and the season.
What stretches the timetable, and what does not
A few factors reliably add time to skylight installation. Others sound as if they should but make little difference.
Access is the first. A roof window that can be fitted from inside the loft may need nothing more than a ladder, while a high three-storey slope or a lantern over a rear extension on a tight terrace may need scaffold or a tower, which goes up before the fitting day. Electric opening rooflights need a supply run by an electrician, although solar-powered versions need no wiring. Weather matters on every type: heavy rain or strong wind stops the roof being opened, so the day may start early or be moved, and a roof is not left open overnight. Blinds, on the other hand, clip in within minutes and do not change the schedule. If you are replacing an existing unit rather than adding a new one, the times are different again, and how long skylight replacement takes sets them out. For timing a project around the seasons, see the best time of year for rooflight work.
Questions people also ask
Can a skylight be installed in one day?
Often, yes. A pitched roof window that fits between rafters, or a sun tunnel, can typically be fitted, lined and made good within one working day. A trimmed rafter, a flat rooflight on a new kerb or a large lantern is more likely to need two days or more.
Do I need to move out while a rooflight is fitted?
No. The work is confined to one room and the roof above it. That room is out of use while the ceiling is open, and there will be some noise and dust, but the rest of the house carries on as normal.
Does adding a skylight to an extension change the timing?
It can shorten the rooflight work itself, because the opening and kerb are built as part of the extension. The earlier the position is fixed, the better; our answer on when a skylight should be planned in an extension explains why.
How do I get a timescale for my own roof?
Every roof is different, so the real timescale comes from looking at it. A light survey confirms the structure, access and product, and the quote sets out the days on site and the lead time. Read more about skylight and rooflight installation in Cambridge, or book a light survey.
