Egress Hinge Sizes: Stack Heights for Fire Escape Windows

Egress Hinge Sizes: Stack Heights for Fire Escape Windows is a practical look at how hinge stack height affects escape routes, compliance and day to day operation. Whether you are a homeowner fitting a new escape window or a trade installer specifying hardware for a block of flats, understanding egress hinge sizes and how to measure stack heights will help you get the right product for a safe, compliant installation.

What is a hinge stack height and why it matters for egress windows

Stack height describes the offset a hinge creates between the face of the frame and the axis of the hinge; in other words, how far the sash sits out from the frame when closed. That offset determines the sash projection, clearance to plaster and beads, and the effective clear opening when the window is used as an escape. With egress windows the stack height is especially important because any added offset reduces the unobstructed opening available for escape.

Common egress hinge sizes and typical stack heights

Manufacturers typically offer a range of hinge stack heights to suit different profiles and reveal depths. Common stack heights you will see in the UK market include:

• 11 mm and 13 mm: low profile; used where flush sightlines and maximum clear opening are required.
• 15 mm and 18 mm: standard for many timber and aluminium casement windows; a good compromise between clearance and strength.
• 20 mm and 22 mm: taller stacks used where thicker beads, deeper frames or additional clearance are needed.
• Specialist heights: some systems or security hinges use bespoke stack heights to match particular profiles.

For egress hinges the most commonly specified sizes are in the 15 mm to 22 mm range, but always measure the actual opening requirements before specifying.

Types of egress hinge mechanisms

There are a few hinge types commonly used for emergency escape windows:

• Quick-release/fast-release hinges: allow the sash to be removed from the frame without tools, giving a larger clear opening quickly; available with various stack heights.
• Removable-pin hinges: the pin can be lifted out to release the sash; simple and robust for occasional use.
• Friction or stay-assisted egress hinges: provide controlled opening and can hold the sash in the escape position; be careful as friction must not impede quick evacuation.

All these variants are produced with different stack heights; selection depends on frame geometry and the required clear opening.

How to measure stack height: step-by-step

Accurate measurement saves time and avoids returns. Use these simple steps:

• Open the sash slightly and remove any beading if safe and practical. If you cannot remove the beading, measure externally and note the possible tolerance.
• Measure from the face of the frame (the surface that the sash closes against) to the centre line of the hinge pin; that is the conventional way manufacturers quote stack height.
• If you cannot access the pin centre, measure the projection of the sash from the frame face when closed; compare with manufacturer datasheets for the nearest stack height.
• Record reveal depth and any plaster or linings that will affect the clearance when the sash is fully open.

Specification and trade advice

For trade professionals specifying egress hardware keep these points in mind:

• Match hinge stack height to the window profile; incorrect stack leads to poor closing, rubbing beads and reduced security.
• Check structural fixings: egress hinges carry dynamic loads during escape use; use the recommended screws and backplates for hardwood, softwood, aluminium or steel frames.
• Corrosion resistance: stainless steel or suitably plated finishes are essential on external windows or in coastal locations.
• Security and compliance: where security is required at the same time as egress function, specify anti-tamper or secure-release variants and note any implications for firefighters or building control.
• Keep clear opening requirements in mind: a larger stack height reduces the usable opening; if the opening must meet a minimum unobstructed size, choose a lower stack height or a quick-release system that removes the sash completely.

DIY guidance for homeowners

If you are replacing or fitting an egress hinge yourself, follow these practical tips:

• Do not alter fire-rated glazing or frames yourself; consult building control or a competent installer for any work affecting means of escape or fire resistance.
• Measure twice: take the existing hinge out and measure the stack height directly if possible; photograph the hinge and frame to help suppliers identify a match.
• Choose the correct fixings: long countersunk woodscrews for timber, self-tapping screws or rivets for aluminium; the hinge must be secured into solid material not just into thin face layers.
• Test operation: after fitting, operate the sash through its full travel to ensure there is no binding, that the sash closes firmly and that handle operation is smooth. Check that the release mechanism operates easily without excessive force.
• Maintenance: lubricate pivot points annually and inspect fixings after heavy use; replace worn hinges promptly to avoid failure during an emergency.

Safety, compliance and practical considerations

Always consider regulatory and safety implications. Egress hinges themselves are only part of the escape system: the opening size, sill height, glazing, and route beyond the window are all relevant. For flats and shared escape routes coordinate with the responsible person or building control. Make sure escape fittings do not compromise the window's weather performance or thermal efficiency; use compatible seals and ensure drainage paths are clear.

Recommended Products

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

• In-Line Window Mechanism
• Offset Window Mechanism
• Structural Glazing Tape - 20mm
• Security Glazing Tape
• Top-Hung Window Hinge - Standard

Conclusion and next steps

Choosing the right egress hinge stack height is a balance between maximising clear opening and ensuring the sash sits and operates correctly within the frame. For trade professionals check stack heights against manufacturer data and frame geometry. For homeowners measure carefully, avoid altering fire-rated elements, and use appropriate fixings and corrosion-resistant finishes.

Next steps: measure your existing hinge and frame, compare with supplier datasheets, and if the window is part of an escape route contact building control or a qualified installer to confirm compliance. For further technical information and hinge options see our pillar page: /guides/window-hinges.