Fire Door Hinges: Why Three, and What the Rules Require

Why three hinges, and what specification

In fire, the hinge line carries a charring, distorting leaf that must stay in its frame for the rated period — two domestic hinges allow flex and gap growth at the top corner exactly where hot gases push. Three (or four on tall/heavy/FD60 leaves) hold the geometry. Specification matters as much as count: hinges to BS EN 1935 with CE/UKCA marking and fire test evidence, typically grade 13 (100kg-class, severe duty) for fire doors, in steel or stainless — aluminium and low-melt alloys fail early. Many certifications also require intumescent pads behind hinge blades, replacing the heat path the recess creates.

The defects inspections actually find

• Missing screws — one empty hole per hinge across a block is practically a tradition; every screw bears load in fire
• Wrong screws: short, fat or mismatched replacements that strip or stand proud and bind
• Odd hinges: one failed hinge swapped for whatever was on the van — unmarked, wrong grade, no pads
• Oil leakage and black streaking: worn knuckles announcing end of life
• Paint-locked knuckles on redecorated doors stiffening the swing until closers can't latch
• Packed or shimmed hinges from old gap 'fixes' — sometimes legitimate, often cardboard

Repair rules of thumb

Hinge work on fire doors is like-for-like or better: matching footprint and grade, full screw sets driven into sound timber (repair plugs where holes are stripped — not longer screws into voids), pads replaced where specified, and the swing/closing re-tested afterwards because hinge changes move gaps. Replacing one hinge of a set with a different pattern creates a mixed line with unknown behaviour; on doors that matter, replace as a matched set. It's modest-cost work that keeps a certified leaf certified — versus the slow slide into 'door, fire, nominal, replace' on the next survey.