Window Gearbox vs Full Espagnolette: What's the Difference?

Window Gearbox vs Full Espagnolette: What's the Difference?

Understanding the differences between a window gearbox and a full espagnolette is essential for homeowners and trade professionals specifying, repairing or upgrading casement windows. Both systems convert handle movement into locking action, but they do so in different ways; each has distinct advantages and practical implications for security, maintenance and installation.

What is a window gearbox?

A window gearbox is a compact mechanical unit housed in the window sash that translates the rotational movement of the handle into linear or cam action to operate one or more locking points. Gearboxes are commonly used in uPVC and some aluminium windows; they are often described as espag (espagnolette) gearboxes when they operate cams or rollers against keepers in the frame.

Key characteristics of a window gearbox:

• Small square or rectangular body fitted into the sash edge; standard spindles are usually 7mm or 8mm square.
• Operates cams, rollers or shootbolts that engage into frame keepers close to the handle centre.
• Easy to replace as a single unit; part numbers and screw centres are often stamped on the front plate for identification.
• Suits sash heights where only two or three locking points are required; common on shorter casements and lower-cost windows.

What is a full espagnolette?

A full espagnolette refers to a multi-point locking system that uses rods or bars running the full height of the sash to operate locking points at the top and bottom as well as at the handle centre. The handle movement drives a mechanism that moves these rods; the top and bottom shootbolts or hooks then engage into keepers in the frame.

Key characteristics of a full espagnolette:

• Continuous operation along the sash height: top and bottom locks are engaged simultaneously for stronger security and better compression on gaskets.
• Available in various actions: hook, roller and bolt options are common; hooks are preferred for lateral compression in PVCu and timber frames.
• More suitable for taller sashes, outward-opening French windows and doors where a central gearbox alone cannot provide adequate sealing and security.
• Often specified for PAS 24 or Secured by Design compliance; multi-point engagement increases attack resistance.

Practical differences that affect installers and homeowners

Security: Full espagnolette systems generally provide superior security because they engage multiple points; hooks and shootbolts at the top and bottom make knife-edge or lever attacks harder. A window gearbox with a few cams can be secure for many applications but may not meet the same resistance levels on tall or French-style sashes.

Weatherproofing and compression: A full espagnolette will pull the sash evenly into the frame at several points; this improves weather tightness and reduces draughts. A gearbox with localised cams gives adequate compression near the handle but can allow less uniform sealing across a large sash.

Servicing and replacement: Gearboxes are straightforward to swap out; they are small, inexpensive and widely available. Full espagnolette systems are modular but more complex; replacing a top or bottom rod, or synchronising the mechanism, can be labour intensive and may require specialist parts.

Cost and manufacture: Full espagnolette systems cost more and take longer to install; they are common on premium and security-focussed installations. Gearboxes are cost-effective for smaller windows and projects with budget constraints.

DIY guidance: when you can do it yourself

Replacing a window gearbox is a common DIY job for competent homeowners and basic trade work alike. Typical steps:

• Identify the part: remove the handle and check the gearbox faceplate for stampings such as the backset, spindle size and screw centres.
• Measure the spindle length and centre distances accurately; mismatched spindles are a common cause of faulty operation.
• Order the correct gearbox; keep the old unit for reference. Many suppliers list compatible parts by manufacturer or profile.
• Remove the faceplate screws, withdraw the gearbox, fit the new unit and test operation before replacing the handle. Lubricate moving parts with a light specialist grease; avoid household oils that attract dust.
• Adjust keepers or striker plates if the cams do not engage smoothly; slight frame adjustment may be needed to eliminate binding.

Full espagnolette work is more advanced: you can perform basic maintenance such as tightening rods, lubricating pivots and replacing worn rollers or keepers. However, aligning and replacing top and bottom rods, or correcting synchronisation issues, is best left to experienced glaziers or a window engineer; improper adjustment can impair security and weather performance.

Trade advice for specification and installation

When specifying hardware think about sash size, orientation and expected use: tall sashes and outward-opening French windows should use a full espagnolette for correct sealing and security. For smaller, inward-opening casements; a quality window gearbox with multiple cams may be sufficient.

Always check compatibility with the handle style and spindle length: lever/lever and espag handles have different spindle requirements. Confirm the backset and screw centres against manufacturer drawings before ordering. For replacement jobs, take the old gearbox or espagnolette mechanism to the supplier when possible; matching profiles avoids costly returns.

For compliance work: consult PAS 24 requirements and Secured by Design guidance for projects where certification is required. Multi-point full espagnolette systems are often necessary to meet the test loads and attack resistance criteria.

Common failure modes and troubleshooting

• Stiff or jammed handle: often caused by worn gearbox internals or dirty cam surfaces; first clean and lubricate, then consider replacement.
• Handle returns to neutral position: broken or stripped gearbox gears; replace the gearbox.
• Top or bottom locks not engaging: misaligned rods or failed keepers in a full espagnolette; check for loose fixings and adjust rod length where possible.
• Excessive play in the handle: worn spindle or loose grub screw in the handle; replace handle or spindle as required.

Further reading and parts

For more detailed information about espagnolette types and keepers see our pillar resource on espagnolette window locks: /guides/espagnolette-window-locks. When ordering parts bring profile measurements or the faulty component to ensure you get the correct replacement.

Recommended Products

Based on this article, you may find these products helpful:

• ERAB Espagnolette Window Lock Universal Lock Replacement
• Avocet Slimline Offset Window Espag
• In-Line Window Mechanism
• Offset Window Mechanism
• E-Type Gasket - Black 5m Roll

Conclusion and next steps

Choosing between a window gearbox and a full espagnolette depends on sash size, security requirements and budget: gearboxes are economical and easy to replace; full espagnolette systems offer superior multi-point security and better compression on larger sashes. For DIY replacements stick to gearboxes and routine maintenance; call a specialist for full espagnolette repairs or where PAS 24 compliance is required.

Next steps: inspect the problematic window, note the spindle size and faceplate markings, and consult a trusted supplier or our trade counter for the correct replacement gearbox or full espagnolette components. If in doubt, book a technician for a survey to avoid incorrect parts and potential rework.