Bay & bow windows across the UK

Bay & bow windows - what to expect

Front bay windows are structural, not decorative - which is what separates a proper £2,800 bay replacement from a £1,200 quote that ends in cracked plaster and a sagging bay roof six months later. The bay frame carries load from the wall above (often a two-storey bay carrying a bedroom and a small pitched roof) and any replacement has to preserve or replace that structural role. Three or five panel bays on 1930s semis are by far the most common configuration in UK housing stock, and where most of the price variation lives.

A like-for-like three-panel UPVC bay on a typical semi runs £1,600-£2,400 fitted, including a new structural bay pole (a steel or aluminium column disguised inside the frame corners that carries the load the old timber bay carried), fresh cills, and reinstatement of internal plaster and external render bands. A five-panel splayed bay on a bigger Edwardian semi is £2,800-£3,800. If the existing bay roof is tiled or leaded and needs stripping and re-covering, add £600-£1,400 for that trade separately.

The failure mode on cheap bay replacements is missing bay poles. An installer who removes the original frame without a proper structural jack and column above the new frame will initially get away with it - until the wall above settles onto the new (weaker) frame and starts cracking at the corners. Any bay window quote should explicitly say 'structural bay pole to load-bearing corners' on the specification. If the surveyor doesn't measure the wall above, ask them why.

Typical UK price range for bay & bow windows: £1,600 - £3,800 installed. Actual figures for your city sit on the city page below.