How do I adjust a UPVC window that will not close?

UPVC windows are adjustable by design and almost nobody knows it. A window that has become stiff, will not latch, or lets a draught through one corner is usually correctable in half an hour with a hex key.

Safety

Step by step

1. Clean and lubricate before adjusting anything.Grit in the hinge track and dried-out mechanism account for a surprising share of stiff windows. Clean the frame and hinge channels, then apply a light machine oil or a silicone spray to the hinges and locking points.
2. Work out which way it is out.Close it slowly and watch where it catches. Catching at the bottom of the handle side means the sash has dropped. Catching at the top means it has lifted or racked. Even all round means compression rather than alignment.
3. Find the adjustment on the hinges.Open the window and look along the hinge arms. There are usually two or three screws — one for height, one for lateral position, sometimes one for compression at the hinge end. Many are hex, some Torx.
4. Adjust in small increments.A quarter turn at a time, then close the window and check. Large adjustments overshoot and it becomes hard to know where you started. Count your turns so you can go back.
5. Lift a dropped sash at the hinge.The most common fault. The height adjustment on the hinges raises the free corner. Support the weight of the sash while adjusting so the screw is not fighting the load.
6. Adjust the keeps for compression.The metal keeps on the frame that the locking cams engage. Most have an eccentric or a slotted fixing that moves them a millimetre or two in or out — that is what sets how hard the window pulls against the seal.
7. Balance compression against operation.Too loose and it draughts; too tight and the handle is hard to turn and the seal compresses permanently. Aim for firm but operable with one hand.
8. Check the seal itself.A perished, flattened or displaced gasket cannot be fixed by adjustment. Replacement gasket is sold by profile and pushes into the channel.
9. Check the handle and gearbox.If the handle turns but the cams do not move, the espagnolette gearbox has failed. It is a replaceable part, and worth measuring carefully — they come in many backset and spindle sizes.
10. Look at the frame if adjustment does not reach.A frame that has bowed, or a lintel that has settled, moves the whole opening. Adjustment has a limited range, and beyond it the problem is structural rather than mechanical.
11. Lubricate again when finished, and annually.Hinges, cams and keeps once a year. It is a five-minute job that prevents most of what this guide is about.

Tips

• Photograph each hinge before touching it and note the starting position of every screw. Getting back to where you started is the safety net.
• Do not use oil on the rubber gaskets — it degrades them. Silicone spray is safe on both metal and rubber.
• If the window is still under a fitting guarantee, adjusting it yourself may affect that. Check before starting.

Common mistakes

• Adjusting without supporting the sash — The screw is taking the full weight of the glass, so the adjustment fights the load and can strip. Take the weight first.
• Overtightening compression to stop a draught — It permanently flattens the gasket, so the seal is worse afterwards and the handle becomes hard to operate.

If it doesn't work

Questions people ask