How long a VELUX installation takes

A single VELUX centre-pivot or top-hung window, dropped into a tiled or slated pitched roof where the rafters are already spaced to suit, is a one-day job for a two-person team. That covers stripping the tiles back around the opening, cutting and trimming the rafters, building the timber surround, fitting the window and its flashing kit, weathering it back in, and forming the internal plasterboard reveal ready for decoration. You lose the daylight hours and you get your room back the same evening.

The reason that figure is reliable is that VELUX built the system around it. The window arrives as a sealed unit with a flashing kit matched to your roof covering, so the fitter is assembling known parts rather than improvising a weathering detail on the roof. The tolerances are designed so that a standard size sits between rafters at their common spacing with minimal cutting. When the roof cooperates, the pace is set by the covering and the weather, not by the window.

Where the day stretches is almost never the window itself. It is everything around it: getting up to the roof, getting the old covering off cleanly, and dealing with whatever the original builder left behind in the loft. Those are the variables the rest of this guide walks through.

It helps to see where the time actually goes, because the visible part, the window going in, is a small slice of it. A typical single-unit day breaks down roughly like this.

• Set up and access, 30 to 60 minutes. Scaffold or a roof ladder, dust sheets inside, and clearing the working area in the room below. If a tower or scaffold went up on a previous visit this shrinks to almost nothing.
• Marking and opening the roof, 1 to 2 hours. Setting out the position from inside, then stripping tiles or slates back to expose the rafters and cutting the felt or membrane.
• Structural trimming, 1 to 2 hours. Cutting the rafters if the opening crosses one, then fitting the trimmers above and below to carry the load around the new hole. This is the part that varies most.
• Fitting the window, 45 minutes to 1 hour. The unit is offered up, fixed to the surround, checked for square and for smooth operation, and levelled.
• Flashing and weathering, 1 to 2 hours. The flashing kit goes on, the covering is dressed back around it, and the roof is made watertight. On slate this takes longer than on plain concrete tile.
• Internal finishing, 1 to 2 hours. Insulating the reveal, boarding it out, and forming the splayed plasterboard lining. Plastering and painting are usually a separate trade on a separate day.

Add those up and a clean job lands inside a working day. The spread in every line is where a difficult roof turns one day into two.

These are industry-typical durations for common jobs, assuming a competent two-person team and reasonable access. They are a guide to the shape of the work, not a fixed schedule, because the roof always has the final say. Where a job needs scaffold, treat scaffold hire and strike as separate calendar days either side of the fit itself.

Read the calendar-span column rather than the on-roof column if you are planning around the disruption. On-roof time tells you how long the fitter is working. Calendar span tells you how many mornings you are living with dust sheets and an open room, which is usually the number you actually care about.

Five things move the clock, and they stack. On an awkward roof you can meet three of them on the same job.

Access and height

A bungalow or a single-storey rear extension is reached from a tower or a roof ladder in minutes. A window going into the main roof of a two or three-storey house usually needs scaffold, and scaffold is its own timeline: it is erected on one day, the fit happens on another, and it is struck on a third. The window still only takes a day to fit, but the job now spans the best part of a week from first van to last. Terraced streets where there is no side access, and the scaffold has to be carried through the house, add a morning at each end.

Roof covering

Plain concrete or clay tiles come off and go back quickly, and the flashing kit is designed to sit into the courses cleanly. Natural slate is slower at both ends: slates are nailed individually, they break if handled carelessly, and dressing them back neatly around a flashing takes a patient hour or two more than tile. Old handmade clay peg tiles, which turn up on the Victorian and Edwardian stock along the Southend cliff, need the same care. If your roof is slate, budget for the longer end of every timing above.

Whether the opening already exists

Swapping a tired VELUX for a new one of the same size is the fastest job on the list, because the structural opening, the trimmers and the internal reveal are all already there. The fitter removes the old unit, checks the surround and the timbers, fits the new window into the existing hole, and re-weathers it. That is a half-day of on-roof work in most cases. Cutting a brand-new opening into a roof that has never had one adds the whole structural stage back in.

Structure under the covering

A standard window sized to fit between rafters at their common spacing needs one rafter cut at most, and often none. A wider unit, or one positioned where it crosses two rafters, needs proper trimming above and below to carry the load around the opening, and a building inspector will want to see it done correctly. Trussed roofs, common on post-war and new-build estates around Shoeburyness and Basildon, are the bigger job: you cannot simply cut a truss, so the design has to spread the load and that is a slower, more considered piece of carpentry than trimming traditional cut rafters.

What sits directly below

If the ceiling under the new window is open loft space the internal side is quick. If it is a finished room, the plasterboard reveal, the insulation detail and the making-good all have to be done to a standard someone will look at every day, and that finishing work is what most often runs into a second visit. Plastering and decorating are separate trades on their own days regardless.

Two windows do not take twice as long as one, and it is worth understanding why, because it changes how you brief the job. The set-up, the access and the making-good scale far less than linearly. Once the scaffold is up and the team is on the roof, adding a second opening a couple of metres along is more structure and more flashing but very little more set-up. Two windows side by side, sharing a run of combi-flashing between them, are a day and a half of work rather than two full days.

A loft conversion is a different question entirely, because the window stops being the job. When VELUX windows go into a conversion they are one line item inside a build that runs for weeks: structural steels, dormer or rooflight framing, insulation to current standards, staircase, electrics, plastering and the rest. The windows are usually installed early, as soon as the roof is opened up and made weathertight, so the interior can be worked on dry. Do not judge that timeline by the window. Judge it by the conversion, and expect the glazing to be in place long before the room around it is finished.

If you are having several units fitted purely as rooflights rather than as part of a conversion, the run of three or more in the table above is the pattern to plan around. This overlaps with our wider VELUX window installation work, where the survey sets out every opening before anyone touches the roof, so the structure and the flashing are worked out on paper rather than discovered halfway through.

People sometimes assume that a higher-specification unit, the kind with solar-control glass for a south-facing slope, is a slower or more involved fit. It is not. A solar-control VELUX goes in on exactly the same timeline as a clear one, because the difference is inside the sealed glazing unit, not in how it fixes to the roof. The flashing, the trimming and the weathering are identical. You pay for the glass in the price of the window, not in days on the roof.

What genuinely earns time, and earns it before anyone opens the roof, is the survey. Southend faces south across the Thames Estuary, which is unusual for an English seaside city and it changes what a good specification looks like here. A window going into a south-facing rear-extension roof or a south-facing loft slope is collecting the summer sun almost square-on, with an open horizon over the water and reflected light off the estuary on top of it. The same window on a north slope has a completely different job to do. Deciding which glass goes into which opening is a survey conversation, and it is time spent on the ground rather than on the clock. It does not lengthen the fit. It is the reason the fit is worth doing once, properly, with solar-control glazing on the planes that face the sun and clear glass where every scrap of daylight is welcome.

The practical point for your timeline: expect a survey visit ahead of the installation day. It is short, but it is the visit that stops the fit itself from throwing up surprises, and it is where orientation and glass specification get settled for each opening separately.

The physical work is a day. The regulatory side runs on its own, slower clock, and it is worth knowing where it sits so nothing surprises you.

A new or enlarged rooflight is notifiable under Building Regulations. Part L governs the thermal performance of the glazing, and Part K covers the safety glass overhead. A like-for-like replacement of an existing window into the same opening is treated more simply than cutting a new hole, but new openings need Building Control to be informed and, in most cases, to inspect. On our installations we make that notification to Southend-on-Sea City Council, or to the relevant local authority for your address, as part of the job, so it is not a task that lands on you.

Most homes across the patch fall under permitted development for rooflights, provided the window projects no more than 150mm beyond the roof plane and sits below the ridge, so no planning application is needed. The exceptions matter for your timeline. Flats and maisonettes, listed buildings, and conservation areas are treated differently. Leigh Cliff and Leigh conservation areas carry an Article 4 Direction that removes permitted-development rights for changes to roofing and windows, so a property there needs a planning application where an identical house a mile away would not. A planning application runs to weeks, not days, and it happens well before any fitter is booked. If your home sits in one of those areas, the paperwork, not the roof work, sets your earliest start date, and it is worth checking with the local authority early. Always treat the permitted-development position as general guidance and confirm it for your own address.

So the timeline you actually plan around has three parts: a short survey visit, then the fit itself, which is the one-day-or-so figure this guide opened with, and the Building Control notification running quietly alongside. Only the middle part involves dust sheets.

You can keep the disruption to what it needs to be with a few sensible moves.

1. Clear the room the night before. Furniture out from under the opening, floors clear, anything precious moved. It saves the first half-hour of the fitting day and protects your things from dust.
2. Ask whether scaffold is needed at the quote stage. This is the single biggest driver of calendar span. If scaffold is required, you are planning around a week of access being up, not a single day, even though the actual fit is still one of those days.
3. Book plastering and decorating as a separate day. The reveal is boarded and made ready on the fitting day, but wet plaster needs to dry before it is painted, so the finished, decorated result is a few days out from the window going in. Plan the reveal to be skimmed once the window is in and settled.
4. Group the work. If you are considering more than one window, or a window now and another later, doing them on one visit shares the access and the set-up and costs you fewer disrupted mornings overall. It is the same logic that makes a run of three cheaper per unit than three separate single jobs.
5. Have the survey first. A proper survey settles the size, the position, the structure and the glass for each opening before the fit, which is exactly what keeps the fitting day to a single day. Surprises found with the roof open are what turn one day into two.

Taken together, the picture is straightforward. A single VELUX in a cooperating pitched roof is a day. Slate, height, scaffold, new structure and a finished room below each add time in known amounts, and a loft conversion is a different project measured in weeks. If you want a firm figure for your own roof rather than the ranges here, the survey is where it gets pinned down, and you can ask us for a quote that puts real dates against your particular house. We have been installing skylights and rooflights across south Essex for over fifteen years, every installation carries a ten-year workmanship guarantee, and the day on the roof is the short part. Getting the specification right before it is the part that lasts.