Window frame replacement

Window frame replacement means a new frame, and in practice a new window, so it costs far more than repairing a frame or changing the glass. ExpertSure puts replacing a warped or rotting frame at £350 to £600 per window, and says full replacement is only necessary when the frame itself is damaged, warped or rotting. If the frame is sound and only the glass has failed, you do not need a new frame at all.

None of the price guides we read gives a price for fitting a new frame and keeping the old glass. They treat frame replacement as replacing the window, so we have done the same. ExpertSure does not say whether its price includes VAT, and we treat it as including it, as we do throughout this site.

Window frame replacement: when a frame is beyond repair

ExpertSure sets out when to repair and when to replace. Repair makes sense when the frames are structurally sound and the problem is limited to hardware, seals or individual sealed units. Replacement is the answer when the frame is warped or rotting beyond repair. Its examples show the gap in price:

• repairing a warped uPVC frame costs £150 to £350 per window;
• a partial repair to a rotten timber frame costs £200 to £400 per window;
• replacing a frame that is beyond repair costs £350 to £600 per window.

ExpertSure also offers a rule of thumb. If the total repair bill would exceed 40% to 50% of the cost of replacing the same windows, replacement is usually the better investment. With several tired windows in a house, that point arrives quickly, and replacing every window at once usually costs less per window.

Changing only the glass

If the frame is in good order and the glass has misted, a glazier can swap the sealed unit and leave the frame in place. ExpertSure says this costs a fraction of full replacement. It puts a blown unit at £50 to £140 per window, labour included, depending on size, and labour for repairs at £40 to £60 per hour. The job usually needs two visits, one to measure and one to fit the unit, a week or two later.

So the question to ask is which part has failed. A misted pane is a glass job. A rotten or warped frame is a window job. Ask the fitter to show you where the damage is before you agree to either.

What the rules say about window frame replacement

The building regulations draw the same line. Approved Document L treats the entire unit of a window, including its frame, as a controlled fitting. Replacing glazing, or a window in its existing frame, does not provide one, so that work does not need to meet the energy efficiency requirements. A new frame does, so the new window has to reach the energy limit of 1.4 W/m²K, or a Window Energy Rating of band B or better, and the fitter has to certify it. Our guide to the replacement window regulations sets out how.

What to ask before you order

• Which part has failed, the frame, the glass or the hardware?
• Is a repair or a new glass unit an option, and what would it cost?
• If the frame is being replaced, is it a new window, and what energy rating does it have?
• Who will certify the work, and when will you receive the certificate?

If several windows need work, the price for your type of home shows what the whole job costs. Then get free quotes and compare them with the quote checker.

Source: ExpertSure on double glazing repairs.