You lift the sash and it either won't stay up at all, dropping straight back down, or it judders and binds halfway, and when it's closed a draught whistles through the gap and the whole frame rattles in the wind.
Sash windows are mechanical — they rely on cords, weights and running channels working together — so these symptoms almost always trace back to one specific part of that mechanism rather than the window as a whole needing replacement.
What each symptom is actually telling you
A sash that drops the instant you let go has lost its counterbalance — the cord has failed. A sash that rattles in the wind but holds its position points to worn beads or gaps rather than a cord problem. A sash that binds or juddgers partway through its travel is usually paint build-up or a swollen, distorted timber section rubbing in the run.
Causes, in order of likelihood
These are the classic sash window faults, and in most cases more than one is present together, since they tend to develop over similar timescales.
- Broken sash cords, which have simply worn through after years of use
- Paint build-up inside the running channels, narrowing the gap the sash needs to slide through freely
- Worn or painted-solid parting beads, the thin strips separating the two sashes and guiding their movement
- Rot in the bottom rail or the cill beneath it, from years of water sitting at the lowest point of the frame
How to tell them apart
Check whether the sash holds its position anywhere along its travel. If it drops immediately from any height, that's consistent with a failed cord on one or both sides. If it holds at some heights but not others, or judders, that points more towards paint build-up or a swollen section.
Look at the parting beads for a build-up of old paint layers, or for visible wear where the sash has been rubbing against them for years — either can cause both sticking and rattling depending on where the wear is.
Press firmly on the bottom rail and the cill with a fingertip or a small blade. Timber that feels soft, spongy or crumbles slightly is rot, and this needs identifying before any cord or bead work, since it changes what the repair involves.
Self-diagnosis before calling a joiner
Test each sash individually rather than assuming both windows in a pair share the same fault, since cords, beads and rot can each affect one sash without the other, and a joiner will want to know which specific sash does what.
Lift each sash to a few different heights and note where it holds, drops or judders, and check the bottom rail and cill with a fingertip for softness. This record makes for a far more useful first conversation than simply saying the window rattles.
Why the problem tends to recur
Repairs that only address the symptom currently causing the most annoyance — say, renewing a cord while leaving paint-choked channels untouched — tend to see a related fault appear again soon after, since the parts of the mechanism are interdependent.
Rot left unaddressed at the bottom rail, even where cords and beads have been renewed, will continue to spread with each wet season, eventually undermining whatever other repair work has already been carried out.
Common questions
Can I just add more weight to stop the sash dropping?+
No — the weights are matched to the sash's own weight through the cord and pulley system, and forcing extra weight in is not a safe or lasting substitute for replacing a broken cord.
Is it normal for old sash windows to rattle a bit?+
Some minor movement is normal in older sashes, but persistent rattling in wind usually means the beads or draught seals have worn beyond what's reasonable and are worth addressing, both for comfort and to reduce heat loss.
How urgent is rot in the bottom rail?+
It's worth acting on promptly rather than through another winter, because rot in timber exposed to repeated wetting tends to spread faster once established, and it can eventually compromise the sash's structural integrity.
Book a free inspection of your sash windows
We'll check the cords, beads and timber condition on each sash and tell you plainly what's causing the sticking or rattling.