Window Lock Repair & Replacement: Espag Mechanisms, Troubleshooting & Insurance

Max the Locksmith · July 2026

The short answer: window locks fail in two places — the visible handle, and the espagnolette mechanism hidden inside the sash edge — and both are repairable parts, never a reason for new glazing. This guide walks the diagnosis, the older lock types you might have instead, and the insurance small print that makes window locks worth taking seriously. Max stocks the common espag patterns, handles and keeps in the van; labour is a flat £85 + parts (+ VAT), parts averaging £10–£80 — price guide.

Know what’s actually locking your window

Open the window and turn the handle while watching the sash edge: little mushroom-headed cams slide along a metal faceplate and, when closed, tuck behind keeps screwed to the frame. That strip is the espagnolette (espag) — the window-scale version of a door’s multipoint mechanism. The handle is only the driver. Longer or older windows may add shootbolts firing into the frame at top and bottom, exactly as on French doors.

So “my window lock is broken” is really one of four faults, and you can name yours in a minute:

Handle turns, cams don’t move → stripped handle spindle or gears — the cheapest outcome.

Handle stiff or solid, window open or closed → the espag itself has seized or stripped internally.

Handle fine, window open; won’t lock when closed → the cams are missing their keeps because the sash has dropped on worn hinges — an alignment fault wearing a lock costume. Shiny scrape marks on otherwise-dull cams confirm it.

Locks, but you can pull the sash open a few millimetres → keep drift or gasket collapse; the lock is throwing but not gripping. Adjustment, not parts.

Jammed locked shut? Read this before you pull harder

A seized espag usually jams with the window locked — and the failure mode that turns a repair into a headache is forcing the handle until the drive snaps, leaving the window locked with nothing connected to unlock it. Stop at “stiff”. Max frees jammed espags without damage (there are service positions and tricks for exactly this), then replaces the failed gearbox or rods. If the window is your bedroom fire escape, treat a stiff lock as urgent rather than annoying — that’s the one window that must open first time, every time.

Not everything is an espag: the older lock types

Cockspur handles (1980s–90s uPVC) — the handle hooks a wedge on the frame; both wear, both replaceable. Timber casements — clasp fasteners and pin locks; on Nottingham’s Victorian terraces in Sherwood, Carrington and Mapperley these are worth keeping and quietly upgrading with keyed versions rather than replacing sashes. Sliding sashes — fitch fasteners at the meeting rail plus sash stops that limit opening; the classic HMO upgrade. Aluminium frames — clamp and blade latches, still serviceable. All the above are stocked or sourced, same visit, same rates — and all count toward the insurance wording below.

The insurance small print (and HMO angle)

Most UK home policies require key-operated locks on accessible windows — typically defined as ground floor, above flat roofs or extensions, or reachable from a drainpipe. Two things quietly void that condition: locks that no longer throw, and locking handles whose keys are lost. Both are small-parts fixes; a rejected claim isn’t. If you’re reviewing the doors at the same time, the equivalent rule there is BS3621 on final exits — one visit covers both checks, and landlords can fold it into a between-tenants lock change. For the wider what-actually-deters-burglars picture, see how secure are uPVC windows.

Parts stock, and the overnight promise

The van carries espag rods and gearboxes in the common patterns (Maco, ERA, Avocet and equivalents), shootbolt kits, keeps, cockspur wedges and the full handle range — which is why most window lock calls across Nottingham, West Bridgford, Beeston and Arnold finish in one visit. Where a mechanism is genuinely obsolete (some 1990s systems), the window is freed, closed and secured the same day — locked-off sash or temporary keeps, your choice explained honestly — and the correct part fitted when it arrives, usually next morning. Nobody sleeps behind an unlockable window.

What it costs (on average)

Handles average £10–£40, espag mechanisms £20–£80, timber and sash window locks £10–£50, all under the flat £85 labour + VAT, with whole-house rounds sharing one labour charge plus a small top-up per window. The honest caveat: obsolete or specialist mechanisms can occasionally run £250+ in parts — rare, flagged before any work starts, and often avoidable with a compatible modern equivalent. Final figure on the phone first: price guide.

Quick answers

My window won’t lock but the handle feels fine — what’s wrong?

Probably alignment: the sash has dropped and the cams miss their keeps. The hinge guide’s daylight test confirms it in ten seconds. Fixing the hinges usually revives the “broken” lock.

The window is locked shut and the handle won’t move — can it be opened without breaking it?

Almost always, yes — jammed espags have known non-destructive openings. The thing that does break windows is forcing the handle until the drive snaps. Stop, and call: same-day response across Nottingham.

I’ve lost my window keys — do I need whole new locks?

Usually just new locking handles, keyed-alike so one key runs the house. New handles come with their own keys (key cutting isn’t something Max offers).

Are window locks a legal requirement?

Not by statute for homeowners — but insurers require key-operated locks on accessible windows, and HMO licensing expects secure, openable windows. Treat your policy schedule as the rulebook.

What’s a shootbolt and do I have them?

Rods that fire from the sash into the frame top and bottom, driven by the same handle — common on taller windows and French-style openers. Open the window and look for holes or keeps at the head and sill.

Can you upgrade my window locks while repairing them?

Yes — keyed handles on accessible windows, sash jammers and restrictors where they earn their keep, all in the same visit. The sensible-upgrades list is in the window security guide.

Sorted? What most readers check next

• Window repairs — locks, hinges & handles
• How Secure Are uPVC Windows?
• uPVC Window Won’t Open, Close or Lock?
• Insurance-approved door locks (BS3621)

Window lock jammed, or renewal paperwork asking awkward questions? Call 07552 421433 — £85 + parts (+ VAT), no call-out fee, across Nottingham & 20 miles.