A sash window is painted shut when layers of paint glue the sash to its beads or frame. You can often free it by scoring the paint lines with a thin blade and tapping the sash loose. If the paint is thick, or the cords are broken, the sashes need to come out for a proper overhaul.
Why paint seals a sash
Paint is a film, not just a colour. Because of that, when a decorator paints over the joint between a sash and its bead, the paint bridges the gap. Once it dries, it acts like a weak glue.
Over the years this happens again and again. Each coat adds thickness, and the gap shrinks. Eventually the sash cannot move at all. That is common in London homes, because many period windows have been repainted every few years for a century or more.
There are other causes too. Swollen timber, a failed sill and broken cords can also stop a sash from moving. So before you reach for a blade, it helps to work out which problem you have.
First, check whether it is paint at all
Try the sash gently. A painted-shut window feels stuck evenly and does not rattle. However, a window with broken cords may slide freely and then drop. If the sash drops, see our guide to broken sash cord replacement.
Look at the joints too. Paint ridges along the line where the sash meets the bead are the clearest sign. Also check the meeting rail, where the two sashes touch, because paint often seals the gap there.
Swelling is different because timber that has taken up moisture sticks without any paint bridge, and usually frees up in dry weather. If damp is the cause, your sill may be at fault, so look at the timber closely.
A safe way to free a stuck sash
Work slowly, because force breaks things. Old timber and glass are fragile, and one hard yank can crack a pane or split a bead.
First, protect yourself, because paint on older windows may contain lead. The Health and Safety Executive says that lead pigments were widely used in paints for homes until the 1960s and were not removed from all commonly used paint until the early 1980s.
Because of that, we suggest you score the paint rather than sand it, and wipe up any flakes with a damp cloth.
Then run a thin, sharp utility knife or a putty knife along the paint lines. Cut where the sash meets the bead on both sides, inside and out. Repeat along the meeting rail. The aim is to break the paint film cleanly, not to cut into the timber.
Next, tap a wide, flat tool under the sash. Use a block of wood to spread the force, and tap gently along the bottom rail. Move along the sash, not just at one point, because force at one spot can split the timber. Often the sash will release with a small crack.
Finally, work the sash up and down in small steps. Once it moves, rub a little candle wax along the runners. That keeps it moving while the paint is dealt with properly.
What not to do
Some quick fixes cause more harm than good, so avoid them. For example, never force the sash.
Do not prise the sash with a screwdriver in the gap. That marks the timber and can split the bead. Do not use a heat gun or blow lamp either, because it can scorch the timber, crack the glass and, on old paint, release lead fumes.
Similarly, avoid hammering the frame. Shock can loosen the putty or crack a pane. If the window will not shift after a careful try, stop and get advice.
When the sashes need to come out
Scoring works on light paint build-up. Heavily painted windows need more, because the paint has often filled the whole channel. In that case, the joiner removes the bead, lifts out the sashes and strips the paint from the edges and runners.
That job is part of our sash window overhaul. We take the sashes out, strip the edges, ease the fit, check the cords and pulleys, and rehang them so they run freely. Because the work covers the beads and runners, the window should not stick again.
Our sash window repairs page explains the other faults we deal with at the same visit, from broken cords to rotten bottom rails. Our price list gives an overhaul with draught proofing as £188 per window, and sash re-cording and counterbalance as £120 per window. For the bigger picture, see our guide to what sash window repairs cost in London.
Repair or replace?
A painted-shut window is rarely a reason to replace anything, and new glazing will not cure it either. For example, our comparison of slim double glazing and vacuum glazing explains why the sash must run freely first.
The timber underneath is usually fine because the fault is only paint. Even so, if the frame is rotten as well, you may want to compare options. Our guide to repairing or replacing sash windows sets out how to decide.
Councils back repair, too. Wandsworth Council, for example, encourages residents to retain and repair existing original timber windows wherever possible. That advice applies well beyond one borough.
A safety note on stuck windows
A stuck window can be a safety problem as well as a nuisance. If a bedroom window will not open, it cannot serve as an escape route. However, a window that opens too far can be risky around young children. We will look at that balance in our upcoming guide to sash window restrictors and child safety.
How to stop it happening again
Prevention is simple because it takes only minutes. When you repaint, mask the beads and run a blade along the paint lines before the paint fully dries. Then open and close the sashes a few times as the paint dries, so they never bond.
Also avoid thick coats, because thin coats dry harder and leave the gap open. If the timber is bare, prime it first. Then leave the sashes slightly open at the top and bottom while the paint dries, so you can reach the edges.
If you live in a conservation area, check with your council before changing how the windows look. For example, our guide to sash windows in London conservation areas explains why the rules differ between areas.
Painted-shut windows around London
Painted-shut windows are most common in older streets with a long decorating history. For example, Georgian and Victorian terraces among sash window repairs in Islington often have sashes that have been painted dozens of times. Houses converted to flats are also affected, since different owners paint different windows.
In homes across Southwark, former council flats and period terraces sit side by side, and both can suffer. Similarly, Edwardian houses in sash windows across Haringey frequently show the same sticking at the meeting rail.
Next steps
If you cannot free a window safely, do not force it. Photograph the problem and note which windows are affected. Then ask for a free site visit and written quote through our contact page. We handle painted-shut sashes across all Greater London postcodes, and our labour is guaranteed for five years.