Butt hinges — the standard
Butt hinges are the rectangular pair-of-leaves with a central pin design used on most timber and steel commercial doors. They are sized by knuckle length (the height of the central barrel) and by leaf thickness. A standard commercial-grade butt hinge is 102 mm (4 inches) tall and ~3 mm thick.
Most commercial doors use three butt hinges — one top, one bottom, one middle — with the bottom hinge typically carrying around 40% of the load. Heavier or higher-traffic doors use four. Fire doors should always have at least three rated hinges.
Brands you will see on UK commercial doors: Dorma, Frelan, Eurospec, Hafele, Briton, Carlisle Brass. Higher-grade work uses stainless steel ball-bearing butts (smoother action, longer life) over plain steel washered butts.
Pivot hinges — aluminium and glass doors
Aluminium-framed shopfront doors and APG glass doors don't use butt hinges — they use pivots. A pivot is a single point of rotation at the top (top centre) and another at the bottom (bottom pivot or floor spring spindle). The door rotates around these two points like a vertical axis.
Pivot hinges take far higher loads than butt hinges — a 1,200 mm wide glass door weighs 80–100 kg and that mass is concentrated on two points. Worn pivots are the most common "hinge" issue on shopfronts: the door starts to drag, then drop, then drift out of square.
Continuous hinges — high-traffic and high-security
Also called geared or piano hinges, a continuous hinge runs the full height of the door. Load is distributed along the entire edge rather than concentrated at three or four points. They are used on very high-cycle doors (retail back-of-house service doors), heavy security doors, and steel doors where the leaf is heavy enough to torque a butt-hinge fixing loose over time.
Continuous hinges cost more upfront but are effectively service-free for the life of the door. They are the right specification when a butt-hinged door keeps losing alignment despite repeated re-fixing.
BS EN 1935 ratings explained
Hinges sold for UK commercial use are graded by BS EN 1935 with a 7-digit code. Each digit covers one performance characteristic:
Category of use (1–4: light to heavy use), cycles (3, 4, 5, 6, 7, 8: from 10,000 to 1,000,000 cycles), door mass (0–7: up to 160 kg), fire resistance (0 = none, 1 = fire-rated), safety (1 only), corrosion (0–5), security (0–4).
For a typical commercial entrance with 200,000+ cycles a year, you want at minimum 4-7-4-1-1-4-0 hinges (heavy use, 200,000 cycles, 80 kg door, fire-rated, basic security). Fire doors need digit 4 set to "1" — non-fire-rated hinges on a fire door invalidate the door's certification regardless of the rest of the spec.
What actually fails on commercial hinges
In rough order of frequency: fixings loosen (the most common, especially on doors that slam regularly), knuckle wear (causes squeak and drag, more common on plain-bearing butts than ball-bearing), leaf bend (impact damage from carts or vehicles), pin migration (the central pin works its way out — rare but possible on old plain butts).
Catastrophic hinge failure on a butt-hinged door is rare. When it happens it is almost always the bottom hinge giving way under shock loading on a slamming door. The whole door drops 10–20 mm onto the floor and the frame typically has to be repaired too.