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How Long Does It Take to Fit New Windows? A Realistic Guide

Most homeowners are surprised to learn that fitting the windows is the quick part. A typical three-bedroom semi in Glasgow can be done in one to two days, but the wait between paying a deposit and the fitters arriving is usually several weeks. Here is what actually happens at each stage, how long it takes, and what can slow it down.

Published 21 September 2026

The short answer: one to three days on site

For a standard house, allow roughly 30 to 60 minutes per window once the fitters are in a rhythm, plus time for setting up, sealing and clearing away. A one-bedroom flat with three or four windows is normally finished in a morning or a single day. A three-bedroom semi or terraced house with eight to ten windows is usually a full day, sometimes running into a second. A large detached house or a full window and door replacement of fifteen or more openings will typically take two to three days.

Doors add time. A front door with a frame and side panels can take two to three hours on its own because of the extra work getting it plumb, secure and draught-free. Bay windows are the slowest job in the house, often half a day each, as the fitters have to support the roof or upper bay while the old frames come out.

The longer answer: survey to installation takes weeks

The site work is only the last stage. After you accept a quote, a surveyor visits to measure every opening precisely. Windows are made to order, so nothing is manufactured until those survey figures are signed off. Manufacturing lead times in the UK are usually three to six weeks for standard white uPVC, and longer for foiled colours, woodgrain finishes, aluminium or timber. Unusual shapes, arched heads and sash and case replicas can add a fortnight or more.

In practice, most Glasgow homeowners should plan for four to eight weeks between paying a deposit and the fitters arriving. Spring and autumn are the busiest periods, and installers often have their diaries filled several weeks ahead. If you want the work done before winter, it pays to get quotes in late summer rather than October.

What happens on installation day

The fitters normally arrive between 8am and 9am and start with the rooms you most want finished first, or work systematically from one end of the house. Each old window is removed, the opening is cleaned back and checked, and the new frame is fixed, levelled and sealed. Internal trims and external silicone are finished before moving on. A good team leaves no opening exposed overnight, so a two-day job still means the house is secure and weathertight at the end of day one.

You will need to clear a metre or so in front of each window, take down blinds and curtains, and move anything fragile off sills. Expect some dust despite dust sheets, especially in older stone tenements and Victorian villas where the surrounding plaster can be fragile. Handles and locks are checked, and the fitter should show you how each opener works before leaving.

What can make the job take longer

The most common delay is discovering rot or crumbling stone behind the old frames. In older Glasgow properties with original timber sash and case windows, the surrounding sill or lintel can need repair before a new frame goes in, which may add a few hours or a return visit. Rendered or harled walls can also crack around the opening when old frames are removed and need making good.

Weather matters less than people think, since fitters work in rain for most of the year here, but heavy wind can stop the installation of large panes for safety reasons. Access is another factor. A tenement flat on the third floor with no lift, or a rear elevation that needs scaffolding or a tower, will slow the day down. Listed buildings and conservation areas add a planning stage before anything is ordered, which can add several weeks to the overall timeline.

Planning your installation realistically

Ask your installer for three things: the expected manufacturing lead time for your chosen product, a provisional installation week, and an honest estimate of days on site. A fixed date is usually only confirmed once the frames are delivered to the installer. If timing is critical, for example around a house sale or a new kitchen going in, say so at the quote stage so it can be built into the schedule.

Most homeowners find the disruption is far shorter than they feared. One or two days of noise and dust, with a working home at the end of each day, is a small price for windows that should last twenty-five years or more.

Common questions.

Do I need to stay at home while the windows are fitted?
Someone should be there at the start to walk through the job and at the end to check the work, but you do not need to stay all day. Many customers leave a key with a trusted neighbour or come back at lunchtime.
Can new windows be fitted in winter in Scotland?
Yes, installers work all year round and each opening is only exposed for a short time. Heavy wind is the main thing that can stop work, not cold or rain.
How long after the survey will my windows arrive?
Standard white uPVC typically takes three to six weeks to manufacture after the survey is signed off. Coloured, aluminium, timber or unusually shaped windows can take longer, so ask for the lead time when you place the order.

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