How to Fit Window Restrictors and Window Locks
Fit window restrictors and locks on UK casement windows for child safety and security, including types, fixings, uPVC versus timber and fire escape considerations.
Open windows are a hazard for young children, and unlocked windows are an easy way in for opportunists. Restrictors limit how far a window can open, and locks keep it shut. Both are inexpensive and quick to fit. The details differ depending on whether your windows are uPVC, aluminium or timber, and whether the window is a fire escape.
Restrictors versus locks
- Restrictors limit the opening to a safe gap, often around 100 mm, so a child cannot fall out and a person cannot climb in. Some can be released with a key or a button for cleaning and ventilation.
- Locks stop the window from being opened at all unless a key is used. Many modern uPVC windows have built-in locks.
Some people use both: restrictors for ventilation, locks for night or when away.
Check fire escape requirements
In bedrooms and upper floors, a window may be an escape route in a fire. Make sure that any restrictor or lock can be released quickly by an adult without a hidden key. Keep keys nearby in an agreed place, not in a drawer across the room. Rented properties and HMOs have specific rules, so check them before fitting anything. See landlord repair responsibilities and handyman work in rented homes.
Choose the right product
- Cable or wire restrictors. Fixed to the frame and sash with a stainless cable. Easy to fit, low cost.
- Friction stay or hinge restrictors. Built into the hinge or stay of the window, suitable for uPVC casement windows.
- Lockable handles. A window handle with a key, replacing the existing one.
- Surface-mounted locks. For timber sashes and casements, fixed to the frame and window.
- Sash window locks and stops. Specialist hardware for sliding sashes.
For uPVC, check whether the window has a hinge restrictor already, and what the manufacturer allows. Some products are designed for a specific profile.
What you will need
- The restrictor or lock, with screws
- Drill and bits, appropriate for timber or uPVC
- Screwdriver
- Pencil and tape measure
- Safety glasses and gloves
Fitting a cable restrictor, step by step
- Close the window and decide where to put the restrictor, usually the top corner on the hinge side or on the opening side at the bottom.
- Mark the positions for the two parts, one on the sash and one on the frame, so that they will align when the window opens to the desired gap.
- Drill pilot holes. In uPVC, use a small drill bit and take care not to go through the profile into a cavity or the glazing.
- Fix both parts. Use the screws provided, and keep them firm but not overtight.
- Test. Open the window fully against the restrictor and check the gap. Operate the release mechanism, and make sure an adult can use it.
- Check closing. Close the window and confirm that it seals properly.
Fitting a window lock
- Position the lock so that the key mechanism is accessible but not in line with the glass, where a burglar could break and reach it.
- Mark and drill pilot holes, and fix to the sash and frame.
- Test the lock several times with the window open before locking it.
- Store the key somewhere safe but accessible.
For timber windows, make sure the screws go into sound wood. On rotten frames, repair first; see how to fix loose tiles for sealing and general repair principles, and consider draught-proofing at the same time; see how to draught-proof doors and windows.
Common mistakes
- Drilling into glazing beads or sealed units
- Fixing in the wrong place so the window does not open as expected
- Forgetting fire escape needs
- Using unsuitable screws in uPVC
- Leaving keys out of reach
Getting help
A handyman can fit restrictors and locks across a whole house in one visit, particularly alongside other small safety jobs such as fitting smoke alarms. On Compito, you can send a request with your postcode and window types, compare offers from ID-verified local providers, ask questions by message and pay online when you accept.
A worked example: a child's bedroom
A first-floor bedroom has a uPVC casement window. The sensible approach is to fit a restrictor that holds the window at about 100 mm while a key or button override lets an adult open it fully in an emergency. Also move furniture such as beds, chests and desks away from the window so children cannot climb. A handyman can do this in minutes, and the part is typically inexpensive, so the minimum call-out may be the main cost.
Choosing by window material
| Material | Usual option | Watch out for |
|---|---|---|
| uPVC | Hinge restrictor or lockable handle | Drilling into cavities and glazing |
| Timber casement | Surface cable restrictor and lock | Rotten timber that will not hold screws |
| Timber sash | Sash stops and sash lock | Fitting that stops the sash running smoothly |
| Aluminium | Surface-fixed restrictor | Thin frames; use suitable screws or rivets |
Fitting tips
- Pilot-drill every hole, and use stainless fixings outdoors-facing frames.
- Fit at the same height on every window in the property so adults remember where to look.
- Avoid placing locks where a gloved hand cannot reach through a broken pane.
- Keep one spare key in a safe, known place.
Stairs, balconies and landlords
Windows on stairs and landings can be as hazardous as bedroom windows. Tenants should ask the landlord for permission and ask for the work in writing, particularly where windows are a fire escape. Keep this guidance general: your local fire and rescue service can advise on escape routes and alarms.
Frequently asked questions
Do I need restrictors in a rented home?
Landlords may have duties around safety, and some tenancies require restrictors in certain rooms. Check guidance and your agreement.
Can a restrictor be overridden by a child?
Quality restrictors are designed to be difficult for small children but easy for adults. No device replaces supervision.
Will fitting locks affect my window warranty?
It might. Check with the manufacturer or installer, especially if the windows are new.