Why will my window only open a few inches?

A window that stops at 100mm is usually doing exactly what it was designed to do. The important thing is to work out whether it is a safety device before applying any force to it.

What you'll need

• A torch
• PTFE lubricant
• The restrictor key, if there is one

Step by step

1. Look for a restrictor.A short steel cable, a folding arm or a plastic block near the top of the sash, either between sash and frame or fitted into the stay. It is the most common answer.
2. Find the release.Cable restrictors have a small button or slider. Key-operated ones need the key, which is usually the same as the window handle key. Press or unlock and the window opens fully.
3. Ask whether it should be released permanently.Restrictors are fitted for child safety, particularly above ground floor, and are required in some rented and public buildings. Removing one is a decision, not a repair.
4. Check whether it is an egress stay instead.Escape windows have a stay that needs a deliberate action — often a button on the stay arm — to swing past its normal limit. It is not broken; it is waiting for that push.
5. Rule out a jammed stay.If there is no restrictor and no release, the stay itself may have grit in the track, a shoe out of position or a bent arm. It will feel gritty rather than stopping cleanly.
6. Clean and lubricate before forcing.Vacuum the track, wipe it and spray PTFE. Grit is the usual reason a stay binds at the same point every time.
7. Look for a stay shoe that has jumped.The sliding shoe can come out of the track and jam. It sometimes goes back with the sash closed and light pressure — do not force it.
8. Consider the child safety question.If a window is above ground floor and a child can reach it, a restrictor is worth having even if you have to unlock it to clean. Locking restrictors give you both.
9. Do not remove a restrictor from a rented property.It is likely to be there to satisfy a legal duty on the landlord. Ask before altering it.

Tips

• Restrictor keys are usually generic and cost very little to replace. Keep one near the window rather than in a drawer.
• If a restrictor has to be defeated every time you clean the glass, a lockable one designed to be released is the right upgrade rather than removing it.
• A window that used to open fully and now stops has usually developed a fault. A window that has always stopped is doing its job.

Common mistakes

• Forcing a window past a restrictor — The restrictor is designed to resist a real push, so forcing it usually tears the fixings out of the uPVC and damages the sash. The repair is far more expensive than a key.
• Permanently removing a restrictor from an upstairs window — Falls from windows are a leading cause of serious injury to young children, and the device costs almost nothing. Where access is the issue, a key-releasable restrictor solves both problems.

If it doesn't work

Questions people ask