20-Point Sash Window Health Check (Free List)

A sash window fails slowly. A cord frays for a year before it snaps, a bottom rail goes soft under the paint long before you notice a draught, and a pane sits loose in dry putty until the day it rattles out. By the time something is obviously broken, the cheap fix has usually passed.

So on every job we run the same check before we touch a tool. It takes about ten minutes per window and it tells us what is fine, what can wait, and what needs doing now. Here is the full list so you can run it yourself with a screwdriver and a torch.

The 20-point check

Work through one window at a time. Open it, close it, and run the sash up and down a few times before you start so you can feel how it behaves. The checks are grouped into five areas.

Cords, weights and hardware (1 to 5)

1. Sash cords. Look for fraying, flat worn patches, or a cord that has gone stiff and shiny. A cord about to break usually tells you first.
2. Pulleys. Push the cord and watch the wheel. It should spin freely. A seized or squealing pulley drags on the cord and wears it out early.
3. Balance. Raise the sash halfway and let go. It should stay put. If it creeps down or shoots up, the weights no longer match the sash.
4. Lifters and fasteners. Check the lifting hooks and the meeting rail fastener are screwed tight and not pulling out of soft timber.
5. Locks and catches. The fastener should pull the two sashes together firmly, not just sit loosely over the keep.

Seals and draughts (6 to 9)

6. Stile seals. Run a hand down the sides of the sash on a windy day. Moving air means the brush seals in the staff bead and parting bead are worn or missing.
7. Meeting rail. Where the two sashes overlap in the middle is the biggest single gap on most windows. Check there is a seal there and that it is still soft.
8. Bottom rail. The bottom of the lower sash should meet the sill cleanly with no visible light.
9. Rattle. Push the closed sash. Movement means the window is loose in its frame, which is noise in and heat out.

Timber (10 to 13)

10. Bottom rail and sill. Press firmly with a screwdriver tip. Timber that gives, feels spongy, or sinks in is rot, even if the paint looks sound.
11. Glazing bars. The thin bars between panes crack and soften first because water sits on them.
12. Paint. Cracked or flaking paint lets water into the timber. On a pre-1970s house the old paint may contain lead, so scrape gently, wear gloves, and wash your hands before eating.
13. Corner joints. Open gaps at the corners of the sash mean the frame is working loose and water is getting in.

Glazing (14 to 17)

14. Cracked or chipped glass. Note any cracks now. A chip at the edge will usually run further over a hot or cold spell.
15. Loose panes. A pane that rattles is no longer held by its putty and needs rebedding.
16. Putty line. Look for missing, crumbling, or shrunk-back putty around each pane.
17. Misting. If the window is double glazed and you see fog or droplets between the panes, the sealed unit has failed.

Safety and operation (18 to 20)

18. Restrictors. Upstairs windows, and any window a child can reach, should have a working restrictor that limits how far the sash opens.
19. Smooth operation. The sash should slide without jamming, sticking, or needing a shove. A window you have to fight is a window you stop opening.
20. Clear exit. At least one window in a bedroom should open wide enough and easily enough to climb out of in a fire.

What each fail actually means

Not every tick in the fail column is urgent. The point of the check is to sort them.

Fix now: a frayed cord, soft timber in the sill or bottom rail, a loose or cracked pane, and a missing restrictor on an upstairs window. These either get worse fast or carry a safety cost.

Fix soon: worn seals, a tired meeting rail seal, crumbling putty, and flaking paint. None of these will fail tomorrow, but each one is letting water or weather into the window and shortening its life.

Keep an eye on it: a slightly stiff pulley, a sash that creeps a little, light wear on the paint. Note it, check it again next season, and act before it moves into the first list.

The fix for each fail

Most of what the check turns up is a job you can do over a weekend. Here is where to start for each area.

Cords and weights. A broken or worn cord is a set job with a known method. Our step-by-step on replacing a sash cord walks through it, and the waxed cotton sash cord and sash pulleys are the parts most jobs need. If the sash will not stay put, the weights are wrong for it, and the sash window weight calculator works out what you need.

Seals and draughts. Worn or missing seals are the easiest win in the whole check. The full method is in how to draught proof a double hung window, and the draught sealing kit for double hung windows has the carrier and brush seal for one window.

Timber. Soft timber does not mean a new window. In most cases the rot is cut back and the section rebuilt. See fixing wood rot in a timber window, done with a structural two-part wood repair epoxy rather than a soft filler.

Glazing. A loose pane or failed putty is a rebedding job, and you do not need traditional linseed putty to do it. Our guide to reglazing a window without putty covers the method, and the reglaze window bundle has the gear. Wear gloves whenever you handle old glass and wash your hands after.

Safety and hardware. A missing restrictor is a quick fit and a real upgrade. See window restrictors, and for lifters and fasteners the hardware bundle covers a whole window.

FAQ

How often should I run this check?

Once a year is plenty for most homes. Autumn is a good time, before the windows get a hard winter of opening and closing and before you need them sealed.

Can I really do this myself?

The check itself needs nothing but a screwdriver, a torch and ten minutes a window. Most of the fixes it turns up are weekend jobs. A window that has dropped its weights into the box, or one with heavy rot through a joint, is where it is worth getting help.

What is the single most common fail?

Worn or missing seals, by a long way. Almost every older sash window leaks air at the meeting rail and down the sides, and it is also the cheapest and fastest thing on the list to put right.

My sash will not stay open. Is that a cord problem?

Usually it is a broken cord or a sash whose weights no longer match it. Raise it halfway and let go: if it drops, check the cords first, then the balance.