Friction Hinge Sizes Explained: Stack Heights and Lengths

Friction Hinge Sizes Explained: Stack Heights and Lengths

Choosing the correct friction hinge for a window or door is more than matching a product code; it affects operation, security, weather-seal performance and longevity. This post covers what traders and DIYers need to know about friction hinge sizes: what stack height and hinge length mean, how to measure them, practical selection advice and installation tips for reliable results.

What is a friction hinge and why size matters

A friction hinge is a mechanical hinge that allows a window sash to open and stay in position without an additional stay or chain; friction in the hinge mechanism controls the sash movement. Size is crucial because the hinge must sit correctly in the frame and support the sash weight and wind loads. Incorrect sizing can cause poor sealing, rattling, restricted operation or premature wear.

Understanding stack height

Stack height is the combined thickness the hinge creates when the window is closed: effectively the distance between the outer face of the frame and the outer face of the sash where the hinge packs off the window. It determines how the sash sits in the frame and how well the window closes against its gasket. Stack heights vary between manufacturers; common practical ranges in UK practice are about 12mm to 25mm, with typical nominal values such as 13.5mm, 16mm, 18mm and 20mm.

Why it matters:

• If the stack height is too large the sash may sit proud of the frame and fail to compress the weather seal, causing draughts and reduced security.
• If the stack height is too small the sash can bind on closing or the hinge may foul the frame rebate.
• Different profiles and glazing bead depths change the required stack height; uPVC, timber and aluminium frames often need different hinge packings.

Understanding hinge length

Hinge length is the length of the arm that attaches to the sash and the frame. It influences leverage, load distribution and the maximum sash height that can be supported without excessive stress. Common lengths used in the UK market include approximately 200mm, 250mm, 300mm and 350mm; taller or heavier sashes may use 400mm or longer hinges or multiple hinges.

General selection guidance:

• Small sashes (roughly up to 800mm high): 200mm–250mm hinges are often sufficient.
• Standard sashes (800mm–1200mm): 250mm–300mm is common.
• Tall or heavy sashes (over 1200mm): 300mm–400mm or specialist heavy-duty friction hinges, or two hinges per side, are recommended.

Longer hinges spread the load over a greater area and reduce stress on screws and frames; shorter hinges are neater for compact sashes but increase load per fixing point.

How to measure for the right hinge

Accurate measurement prevents costly returns and on-site delays. Follow these steps:

• With the window closed, measure the visible gap: distance from outer face of frame to outer face of the sash where the hinge sits. This gives a quick reference for required stack height.
• Measure sash height and weight if possible; the sash height helps determine hinge length, while weight influences choice of standard or heavy-duty friction setting.
• Check the frame profile: reinforcement channels, glazing bead position and any rebates may affect which hinge model will sit flush.
• Note handedness: left- or right-handed hinges are not interchangeable on some systems; check hinge orientation before ordering.
• Always cross-check with the manufacturer datasheet for the specific hinge series; manufacturers publish exact stack heights, load ratings and recommended sash sizes.

Practical trade advice and DIY guidance

Trade professionals will recognise many practical considerations; for homeowners tackling a replacement, these pointers help keep the job smooth.

• Order hinges in pairs: replace both hinges on a sash at the same time to keep operation balanced and avoid uneven wear.
• Use the correct fixings: stainless steel screws for exposed conditions, and the screw length and type specified by the hinge manufacturer; countersink when required to avoid distortion.
• When fitting to uPVC frames use self-tapping screws suited to the material and be careful not to overtighten; for timber, choose appropriate length and ensure you fix into solid timber, not just thin glazing bead.
• Adjust the friction setting after installation: most friction hinges have a concealed screw or Allen key adjuster; increase friction for heavier sashes, reduce for smooth operation where needed.
• Seal around the hinge pocket where necessary to maintain weather performance; a small bead of compatible sealant will prevent moisture ingress without restricting movement.
• Keep a small selection of stack heights in stock for quick swaps: 13.5mm, 16mm and 18mm cover a lot of typical profiles.

Common problems and how to avoid them

• Incorrect stack height: leads to rattles or failure to close. Avoid by measuring carefully and cross-referencing manufacturer data.
• Insufficient hinge length: causes sagging or excessive load on fixings. Use a longer hinge or add a second hinge for tall sashes.
• Wrong handed hinge: test the orientation before drilling; if in doubt, bring the sash into the workshop to compare.
• Poor lubrication or contamination: periodic light oiling of pivot points prevents stiff operation and reduces wear; do not use heavy greases that attract dust.
• Mixing different hinge series: keep specifications consistent across a project to ensure matching stack heights and bearing characteristics.

When to call a specialist

If a sash is unusually heavy, warped or fixed into a non-standard frame profile, consult a specialist or the hinge manufacturer. Complex refurbishments, especially on listed buildings or with leaded lights, may need bespoke packings or reinforced hinge solutions to preserve both function and appearance.

Recommended Products

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

• In-Line Window Mechanism
• Offset Window Mechanism
• E-Type Gasket - Black 5m Roll
• E-Type Gasket - Black (Per Metre)
• Structural Glazing Tape - 20mm

Conclusion and next steps

Choosing the correct friction hinge involves matching stack height and hinge length to the frame profile and sash size. Measure carefully, consult manufacturer datasheets and use the right fixings and adjustments on site. For traders, keeping common stack heights and lengths in stock speeds up callouts; for DIYers, replacing hinges in matched pairs and following the measurement steps above will avoid the most common faults.

For more detailed technical information on fitting types and hinge families see our pillar resource: /guides/window-hinges. If you need help selecting parts for a specific profile or project, contact Window Hardware Store for trade advice, sample packs or site measuring services.