A like-for-like roof window replacement typically takes half a day to a full day for a single unit. The roof is made watertight the same day and is never left open overnight. The old unit comes out, the new frame goes in with both collars and a matched flashing kit, and the covering is re-hung, all inside one working day when the trimmers are sound.
That is the honest baseline for the job most people are asking about, the straight swap where the opening already exists and the rafters are never touched. What changes the answer is everything that gets added to that straight swap, and it is worth knowing what each addition costs you in time before you book.
Why a straight swap is quick
On a like-for-like replacement the structural opening stays exactly as it is. The reveal is already formed, the trimmers are already in, and the size code has barely moved in twenty five years, so a current unit usually drops into the same hole. There is no cutting, no engineer, and no waiting on structure to be signed off. The clock is really just strip back, set and square the frame, fit the insulation collar and underfelt collar, dress the flashing, and re-cover.
The roof is open for hours, not days, and it is closed again the same afternoon. If weather makes that impossible we sheet, secure and come back rather than pressing on into the dark. We do not leave a roof open overnight, full stop.
What adds time
Every one of these is a reason a job runs longer than a day, and a good surveyor will tell you which apply before you commit.
- Internal plastering. The window itself is quick. Re-forming and skimming the reveal, then letting it dry before decoration, adds a return visit or a second day. On a straight swap where the old lining survives, this often does not arise.
- Scaffold versus a tower. A single-storey rear slope can often be worked from a tower that goes up the same morning. A second-floor terrace slope needs full scaffold, which is usually erected the working day before and struck afterwards, so the access alone stretches the timeline either side of the fitting day.
- Rot found in the trimmers. When the old unit comes out and the timber around the opening has been wet for years, the trimmers have to be cut back to sound wood and rebuilt before the new frame can be set. We photograph it, price it, and only then carry on. This is the most common single reason a one-day job becomes two.
- Multiple units. Two or three windows on the same slope, still like-for-like, is typically one to two days because the access and strip-back are shared but each frame still has to be set, collared and flashed in turn.
- A new opening. Cutting a fresh window into the roof, rather than swapping one that is already there, is a different job. A new opening in a cut roof is around two days per window because a rafter has to be trimmed and doubled trimmers formed. A new opening in a trussed roof depends entirely on the engineer’s designed solution and is quoted individually.
Watertight the same day is the promise. A finished reveal is not always the same day. On any job with plastering in scope, the roof is closed and weatherproof on day one, but the room may need a second visit once the skim has dried. Those are two different milestones and we state both on the quote.
What it means locally
Around Ipswich the timeline is usually set by access and by what the strip-back reveals, not by the window. Terraces off Norwich Road and Spring Road often need full scaffold to reach a second-floor slate slope, so the access adds a day either side even when the fit itself is a clean half-day. The 2000 to 2010 loft-conversion units failing across Chantry and Whitton are mostly straight swaps, quick jobs, unless the timber has gone. Coastal properties at Felixstowe and Harwich are where we most often find rot in the trimmers, because the same salt exposure that killed the old window has usually been working on the wood around it.
Booking and weather
The fitting day is quick, but the lead time in front of it is not instant. Standard sizes and finishes are typically two to three weeks to order, and nothing starts on site until the windows and the flashing kits are physically here, because we will not open a roof waiting on a delivery. Escape-rated units and conservation-style recessed installations run longer. Weather also has a vote: we fit in most conditions, but a hard easterly on an exposed slate slope is a day we would rather move than rush, and we would sooner reschedule than leave a roof half open in driving rain.
Related reading
For the full fit sequence behind the timeline, see our roof window installation process page, or the quick version at how roof windows are installed. If access is your question, scaffolding for a roof window replacement covers scaffold versus tower in detail. And roof window replacement is the wider guide. All of it sits under our main VELUX window installation page.
Get a fixed price and a realistic timeline
The survey is where the timeline stops being an estimate. Once we have seen the covering, the access and the state of the trimmers, you get one written price and a straight answer on how many days it takes, including whether any of it needs a return visit for plastering. That price is fixed, and every job carries a 10-year workmanship guarantee from installers with 25 years fitting roof windows.
Request a fixed quote for roof window replacement in Ipswich, Suffolk or north Essex.
Thinking about this job? We survey across Ipswich, Suffolk and north Essex and give you a fixed price before any work starts, with a 10-year workmanship guarantee.