Timber sash windows were built to be repaired. The cords, pulleys and beads are designed to be replaced every few decades, and the frame itself can last a century if it is kept painted.
How a sash window works
A box sash has two sliding sashes. Each hangs on cords that run over pulleys to cast iron weights hidden in the box on either side of the frame. The weights balance the sash, so it stays where you leave it. Beads hold the sashes in their channels and a parting bead keeps them apart.
Almost everything that goes wrong is one of those parts wearing out, not the window itself.
Signs a repair is enough
The sash sticks or drops, the window rattles in the wind or you can feel a draught around the edges. All of these are fixed with new cords, beads and brush seals.
Paint is the other common problem. Decades of coats build up in the channels until the sashes stick or will not open at all. Freeing them, cleaning the edges and repainting with the sashes in place solves it.
Cracked putty and loose glass look worse than they are. We cut out the old putty, reseat the glass and repaint, and the pane is sealed again.
Signs it is time to replace
Soft wood at the bottom rail or sill that a screwdriver sinks into, or a frame that has moved so far the sashes no longer fit. Even then, we often replace only the rotten section.
Splicing new timber into a rotten bottom rail or sill costs a fraction of a new window and keeps the original glass, which many owners value for its slight ripple.
What a repair involves
A full overhaul of one window usually takes half a day to a day. We take the sashes out, replace the cords, check the weights and pulleys, ease and wax the channels and fit new beads with brush seals. Rotten sections are cut out and spliced. Then everything is primed and painted.
Original glass and old ironmongery are kept and refitted. If a pulley is seized, we free and oil it rather than replace it, so the window keeps its original parts.
We work on two windows at a time and fit temporary boards if a sash has to stay in the workshop overnight.
What it costs
As a rough guide, a full overhaul with draught proofing costs between £350 and £550 per window, depending on its size and the state of the timber. A new timber sash window of the same size costs between £1,400 and £2,200 fitted. Windows that only need cords and seals cost less.
The final figure depends on what we find, and we photograph any rot we cut out so you can see why it was needed.
Warmth and noise
Draught proofing makes the biggest difference to comfort. For more, slim double glazed units can often be fitted into the existing sashes, or you can add secondary glazing on the inside. If your house is in a conservation area, check with the council before changing the glass. We can tell you what is usually accepted.
Looking after them
Repaint the outside every five to seven years, keep the sill clear so water runs off, and open each window fully a few times a year so the cords and pulleys keep moving. That is most of what it takes to keep a sash window working for another century.
Can I do it myself?
Replacing a broken cord is manageable if you are handy: the staff bead comes off, the lower sash lifts out and the new cord is tied to the weight through the pocket in the box. Work on one side at a time and mark every bead so it goes back in the same place. Anything involving rot, glass or the upper sash is easier with two people and the right tools.
Before you decide
Ask for a survey window by window rather than a single price for the house. Often only one or two windows need serious work and the rest need an afternoon each. That is a very different budget from replacing them all.
