Seven signs tell you a sash window needs repair: soft or rotten timber, a snapped cord, rattling, draughts, cracked putty, a sticking sash and persistent condensation. Most are cheap to fix if you catch them early. Left alone, they spread, because water and movement make every fault worse.
1. Soft or rotten timber
Rot is the most serious sign. Press a screwdriver tip into the sill and the bottom rail. If it sinks in or the wood crumbles, water has got in.
Peeling paint and dark patches also point to damp. Since the sill takes the worst of the weather, it fails first. Our guide to rotten sill repair or replacement shows how to test for it and what your options are.
2. A sash that will not stay up
If a window drops shut or will not stay open, a cord has probably snapped. Each sash hangs on two cords, so the window may tilt and jam. It may also feel heavy, because the weight no longer helps. In particular, check whether the sash drops the moment you let go.
This is a routine fix. We cover the details in our post on broken sash cord replacement. Our sash cord replacement service costs £120 per window.
3. Rattling
A rattle means the sash is loose in its frame, although the cause varies. Worn beads, shrunken timber or a failed cord can all cause it. Wind makes it worse, and the noise can keep you awake.
Rattling also wears the window. Each knock loosens joints and cracks paint. As a result, a small fault grows. Our post on why sash windows rattle goes through the usual causes.
4. Draughts
Hold a hand near the meeting rail on a windy day. If you feel cold air, the seals have failed or gaps have opened. You may also see curtains move or dust collect on the sill.
Draughts raise your heating bills because warm air escapes. They also make a room feel colder than the thermostat says. A full overhaul with draught proofing fixes this, and it costs £188 per window.
5. Cracked or missing putty
Putty holds the glass in place and keeps water out. Over time it dries, cracks and falls away. Once that happens, rain can reach the timber behind it.
Look for gaps, flaking paint along the glass edge and loose panes. A pane that moves when you press it needs attention soon, because it can crack. Fresh putty is a small job, but it protects the whole sash.
6. A sticking sash
A sash that jams or needs force to move is a warning. Paint is the usual culprit, because layers build up in the channels. Swollen timber is another, since damp makes wood expand.
Never force a stuck window, though. You can snap a cord or crack the glass. Our guide to painted shut sash windows explains how to free one safely, and our service page on sash window repairs covers the fix.
7. Condensation and damp patches
Misting on the glass is normal on a cold morning. However, water running down the pane or pooling on the sill is not. It can soak the timber and start rot.
Sometimes the cause is a failed seal in a double-glazed unit. Often it is a ventilation issue in the room. Either way, it deserves a look before you spend money.
What to do first
Walk round the house and check every window for these seven signs. Make a list by room. A short list makes a quote easier, and it shows which jobs matter most, since some faults are urgent while others can wait.
Start with anything that lets water in. That means rot, putty and sills. Next, fix anything that makes the window unsafe, such as a broken cord. Finally, deal with comfort issues like draughts and noise.
For upkeep afterwards, our sash window maintenance guide lists the simple yearly jobs. Regular care keeps small faults small.
Should you repair or replace
Repair wins in most cases, because a sash with sound timber and a few worn parts is cheap to restore. We always tell you plainly if a window is past saving. By contrast, a full double-glazed replacement costs £1,480 per window.
Glass is a separate question. If cold glass or noise bothers you, slim double glazing may suit your windows. Our comparison of slim double glazing and vacuum glazing looks at both.
The style of your windows matters too. Georgian sashes have many small panes, while Victorian ones usually have fewer, larger panes. Our guide to Georgian and Victorian sash windows shows how to tell which you have.
Local examples
The same faults turn up across London, although the causes vary. Terraced streets have original sills and rails, so sash window repairs in Lewisham often include both. Period homes in Greenwich and nearby streets often have painted-shut sashes.
Meanwhile, many homes across Brent have Edwardian and interwar windows that need cord and putty work. Wherever you live, the signs are the same.
Getting it checked
We offer a free site visit and a written quote. The quote lists each window and each fault, with the price beside it. You can then choose what to do and when.
Send us your postcode and a short note about the problem through our contact page. Our five-year no-quibble guarantee covers the labour, so you know the repair will last. You can also see every price on our costs page.