How Long Does It Take to Replace Windows? (With Realistic Ranges)

Ask how long it takes to replace windows and you’ll get very different answers. One contractor says two days. Another says six weeks. Both are right — for their own project, in their own house, at their own pace.

The honest answer depends on how many windows you’re talking about, how old the house is, and how much time gets eaten by the gaps between the installer arriving and the decorator coming back to paint the reveals. Here’s what those ranges actually look like, what the time is spent on, and what makes any given project run longer.

The two most common ranges

A single window — one day on site. If the opening is in good condition, the existing frame is sound, and the new window is a like-for-like replacement, a competent installer can remove the old unit, fit the new one, seal it up, and do the basic interior finish in a single day. A few hours of actual installation work, spread across the day with prep and cleanup.

A full-house job — one to three weeks on site. Across an average home with ten to fifteen windows, a full replacement takes a few days of removal, a week or two of fitting and sealing, and a couple of days of cleanup. The spread is mostly about how many openings are irregular (older homes), how many different window styles you’re mixing, and how many installers are on site.

Neither of these numbers includes the time between ordering and delivery, which is the biggest source of delay by far. Windows are often fabricated to your exact size, colour, and glass specification — and that takes time. Add two to six weeks for ordering, depending on the supplier.

The installation itself is only part of the timeline. What happens before and after — ordering, make-good, and decoration — often takes longer than the install.

What the weeks are actually spent on

Window replacement isn’t one continuous block of work. It’s a series of phases, some fast, some slow, and the gaps between them are where projects lose months.

Phase 1: Selection and ordering. Before a single window arrives, there’s a phase most people under-count. You need to decide on frame material (uPVC, timber, aluminium), glass type, colour inside and outside, handle style, and trim profiles. Then you measure, get quotes, place the order, wait for fabrication, wait for delivery, and hope nothing got mixed up in the factory. This phase alone often takes three to eight weeks.

Phase 2: Removal and prep. The old windows come out. This is where you find out if the existing openings are in good shape. In a new build, the openings are square and clean. In a thirty-year-old house, the previous owner’s handyman may have patched things with expanding foam and silicon that’s better left untouched — or you might find rot in the sill that wasn’t obvious from the surface. This phase adds days when it shouldn’t, and nobody sees it coming.

Phase 3: Installation. The new frames go in. Each window is checked for plumb and square, shimmed into position, fixed to the structural wall, and sealed. The installer checks the operation of the opening mechanisms — hinges, handles, locks — before moving to the next one. This is the skilled, visible part of the project. A team of two working on a standard house typically finishes in five to ten days, depending on the number and complexity of windows.

Phase 4: The make-good. The installers leave. The windows work. But the job isn’t done — the reveals still need patching, painting, or re-tiling, the interior trim and architraves need installing, and the exterior flashings and pointing need finishing. This is the phase most people forget to budget for, and it can easily add one to two weeks after the installers have gone home.

What makes a window project run long

Every project has its own delay profile, but there are some that show up again and again:

Out-of-square openings. This is the single biggest time-sink in older homes. If the opening isn’t square — and in a house that’s settled over decades, that’s the norm rather than the exception — each window takes longer to fit because the installer has to shim it in multiple places, adjust the packers, and sometimes cut the frame to fit. A square opening takes five minutes to fit. An out-of-square one takes an hour.

The decorator’s schedule. The window installer finishes in two weeks. The decorator who’s going to paint the reveals and install the trim is booked three weeks out. That means the project sits for three weeks with windows installed but rooms not quite finished. The decorator doesn’t show up for weeks. You’re sitting in a partially decorated house wondering when it’s going to actually feel done.

Wrong order from the supplier. It happens more often than you’d expect. The factory sends size A to the room that needs size B, or a window ordered in white comes in a colour that’s close but not the same. The replacement takes another two to four weeks. The project stops dead while that window sits on a pallet somewhere.

Bay windows and specialty shapes. A standard rectangular sash or casement window is straightforward. A bay window with multiple angles, a curved top, or a casement that opens outward into a tight space is a different proposition. The installer needs to handle more pieces, coordinate more angles, and seal more joints. Expect an extra day or two per unit.

Permits and planning permission. If you’re replacing windows on a listed building, in a conservation area, or in a development with strict appearance rules, you’ll need permission before you order. This isn’t a delay for most homeowners, but it’s worth checking early. You don’t want to spend six weeks waiting for the windows to arrive only to find out you weren’t allowed to change the frame colour.

The bathroom renovation timeline and the rewiring guide both cover the same theme: the visible work is only part of the project, and the invisible gaps between trades are where delays accumulate. Window replacement follows the same pattern.

Even the details — handles, locks, hinges — need to be specified and ordered before the install starts. They’re small things that can stop the entire project if you forget them.

Practical tips for keeping things on track

Lock every specification before ordering. Frame colour, glass type, handle style, trim profile — decide on everything and write it down. A single window out of spec can delay the entire project by weeks while the factory makes a replacement.

Order early and have a fallback plan. Don’t order until you’re ready to commit, but don’t wait until the last week before you want the install to start. If you’re doing a full-house job, order enough lead time for the supplier to get things right. Have a date you want the install to start, count back six weeks, and place the order by that date.

Pre-book the decorator. This is the one most people forget. The decorator who does the reveals and trim needs to be booked for the week after the install finishes. If they’re not booked, your finished windows sit exposed and unfinished while you figure out decoration.

Check the openings before the install day. Walk through the house with the installer or their estimator and flag any windows that look like they might have rot, structural issues, or previous bad repairs. This lets you budget extra time for those specific units.

Document your choices. Every window in your house gets a slightly different treatment — bay windows, bathrooms, upstairs bedrooms — and keeping track of which windows have which specs is harder than it sounds. A simple list, a spreadsheet, or a project tracker in an app like Home Stories, where you note the frame colour, glass type, handle style, and supplier for each room, can save you from ordering the wrong thing or arguing with yourself about what you decided three months ago.

When the whole thing feels manageable

If you’re replacing a few windows in an older house and you’re feeling overwhelmed by the timeline, here’s the thing: window replacement is one of the more predictable renovation projects you can take on. The trades involved — an installer and a decorator — are straightforward, there’s no plumbing or electrical to coordinate, and the house stays habitable throughout.

The delays are mostly about ordering and make-good, which means they’re preventable. Order early. Book the decorator. Write down every specification. Check the openings before the install starts. If you do those four things, a full-house window replacement in an average home typically finishes in three to five months from first decision to fully decorated, with the actual on-site work taking a fraction of that time.

A similar planning approach works for any renovation project, of course. If you want to think about how a step-by-step renovation plan fits into this kind of timeline, or how to track what you’re spending across multiple trades, those posts go into the wider process that window replacement is a part of.

The bottom line

A single window takes a day. A full-house job takes one to three weeks of on-site work, plus two to six weeks for ordering and delivery, plus one to two weeks for the decorator to come back and finish the reveals. That’s roughly two to five months from first decision to fully decorated, and maybe as little as six weeks if everything lines up perfectly and you’re replacing a small number of straightforward units in a new build.

The gap between the installer leaving and the house feeling done is almost always longer than the install itself. Plan for that. Book the decorator early. Write down every specification. And keep a record of what you chose — not just for the installers, but for yourself, years from now when you need to replace that one window in the bathroom and can’t remember what colour the frames are.

A renovation contingency budget is the other piece of practical advice that applies here: the budget line that exists for when the installer finds rot behind the old frame or the decorator’s reveal work turns out to be more extensive than expected. It’s not a failure to have one. It’s planning for the reality that older homes always have surprises.

If you’re managing a renovation at all — whether it’s ten windows or ten rooms — a single place to keep track of decisions, budgets, and tasks makes the whole process considerably less stressful. Home Stories is a free iPhone app that does exactly that: budget tracking, task lists, before-and-after photos, and PDF reports, all synced across your devices. No account needed, works fully offline.