Fit sash window stops and locks

Fit sash stops and a sash lock to control how far your window opens and secure it shut.

SW-01Clear the area and check the sash runs freelyOpen and close the sash a few times before you fit anything, to check it runs smoothly on its cords or spiral balances. Lay a dust sheet over the sill and floor below to catch dust and dropped screws. Wipe down the frame and sash where the hardware will sit, so the screws grip clean timber.

1 each · Dust sheet

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1 each · Cloth

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SW-02Choose the right hardware for the jobA sash lock (or sash fastener) fits on the meeting rail — the horizontal bar where the top and bottom sashes overlap — and pulls them together so the window can't be forced from outside. Sash stops are separate screw-in fittings on the sash stile that limit how far the bottom sash can open, good for ventilation without leaving a gap big enough to climb through. Fit a lock if you mainly want it secure when shut, and stops as well if you want to leave it safely ajar. These fittings are for timber sashes; if yours are uPVC, use the matching fittings sold for that system instead, as ordinary wood screws won't hold in plastic profile.

1 each · Sash lock (fastener)

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1 pair · Sash stops

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SW-03Mark the lock position on the meeting railClose the window fully. Hold the sash lock centred on the meeting rail, check it's level, and mark the screw holes through the fixing plate with a pencil. Use a bradawl to make a small starter dent at each mark so the drill bit doesn't wander on the timber.

1 each · Pencil

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1 each · Bradawl

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SW-04Drill pilot holes and fit the lockYou're drilling into solid window timber here, not a wall, so there's no need to check for cables or pipes. Drill a pilot hole about 2mm smaller than the screw at each mark, stopping short of the far side of the rail so you don't punch through. Screw the lock on by hand or with the drill on a low torque setting, then test that it pulls the sashes together and locks smoothly.

4 each · Wood screws (supplied with lock)

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1 each · Pilot drill bit 2mm

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SW-05Mark and fit the sash stopsOpen the bottom sash to the maximum gap you want it to stop at — 100mm is a common setting for secure ventilation. Hold each stop against the sash stile at that height, mark the screw holes, then bradawl and drill pilot holes as before. Fit both stops at the same height on each stile so the sash stops evenly on both sides.

4 each · Wood screws (supplied with stops)

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1 each · Pilot drill bit 2mm

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SW-06Check whether this window is a fire escape routeIf this window is the main escape route from a bedroom or other habitable room, Building Regulations guidance (Approved Document B) says it needs a clear opening of at least 450mm wide and 450mm high, with the bottom no higher than 1100mm from the floor, and it must open without a key or tool. If you fit stops here, use a type with a quick-release catch anyone can operate by hand, so nobody is trapped in a fire. On windows that aren't an escape route, a fixed screw-in stop is fine.

RULES

KNOW THE RULES

Windows used as an emergency escape route must meet Approved Document B guidance on minimum opening size and be openable without a key. Don't fit a stop or lock that blocks this on an escape window.

SW-07Test and tidy upOpen and close the window fully several times to check the lock engages easily and the stops hold firmly at the height you set. Vacuum up dust and any dropped screws from the sill and floor, then wipe down the frame.

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