Fire doors for commercial buildings

A fire door’s rating describes how long it can hold back fire under test conditions, expressed in minutes: FD30 for 30 minutes, FD60 for 60 minutes, with FD90 and FD120 used less commonly in specialist applications. The rating applies to the complete door assembly, tested to BS 476-22 or the more recent BS EN 1634-1, not to the leaf on its own, which is why a certificated FD30 door fitted with the wrong seals or an incompatible frame can fail well short of its rated time.

Which rating a location needs comes from the building’s compartmentation strategy, usually set out in the fire risk assessment or the original building design. Escape corridors and stairwell doors in a typical office or retail unit are often FD30, while higher-risk areas such as plant rooms, comms rooms, kitchens and riser cupboards, or doors protecting a route used by a larger number of people, are more likely to need FD60. We work from that strategy rather than defaulting to one rating across a building, because over-specifying doors adds cost without adding protection, and under-specifying leaves a genuine gap.

A fire door depends on several smaller components working together, and each one has a specific job.

Intumescent and smoke seals. Intumescent strips are set into the door or frame and expand rapidly when exposed to heat, sealing the gap between the door and the frame as the fire develops. Smoke seals, sometimes combined with the intumescent strip in a single product, block the passage of cold smoke before the fire has generated enough heat to trigger the intumescent element. Both need to be continuous and undamaged, because a gap in the seal is a gap in the door’s protection.

Self-closing devices. A fire door only works if it is shut, so escape route fire doors are fitted with a self-closing device, usually an overhead door closer, that returns the door to a fully closed and latched position after every use. The closer needs enough force to overcome the door’s own resistance and any air pressure difference across it, without slamming or making the door too heavy for someone to open it in an evacuation.

Hinges and hardware. Fire doors are hung on fire-rated hinges, generally three per leaf, that keep the door aligned in its frame and stop it dropping or binding as the frame heats and moves during a fire. Locks, latches, vision panels and any other ironmongery fitted to the door also need to be rated for use on a fire door, since standard hardware can compromise the assembly even when the leaf and frame themselves are correct.

A fire door needs checking regularly, not just at installation, because the things that stop it working, wedges, worn seals, dropped hinges, are usually caused by everyday use rather than a fault in the door itself. A widely used five-step check covers most of what an inspection needs to confirm: the certification label is present, the gaps around the door are consistently no more than about 4mm when closed, the seals are intact with no damage, the hinges are firmly fixed with no missing or broken screws, and the door closes fully onto its latch without sticking or being held open. We carry out fire door inspections against this standard and a more detailed check of the wider assembly, recording what we find and what condition each door is in.

The most common defects we come across are straightforward but serious: doors propped open with a wedge or fire extinguisher, damaged or missing intumescent and smoke seals, self-closers that have been disconnected or adjusted so the door no longer latches, hinges with missing screws, and doors that have been cut, drilled or altered on site to fit new hardware or accommodate cabling, which can void the certification even where the change looks minor. Where an inspection identifies a defect, we carry out the remedial work needed, whether that is replacing a seal, adjusting or fitting a new closer, or replacing a door that has been compromised beyond repair, and record what was found and what was done about it.

What a fire door needs to achieve stays consistent, but where doors are required and how heavily they are used varies by premises. Offices generally need fire doors on escape corridors, stairwells and plant rooms, often with hold-open devices linked to the alarm system on busy circulation routes. Retail units need doors that hold up to constant public traffic without seals or closers wearing out early. Warehouses and industrial premises often need FD60 doors around higher-risk processes and storage areas, alongside larger doorsets sized for the building. We take these differences into account across the industries and premises we work with, rather than applying one specification everywhere.

If you need fire doors surveyed, installed, brought up to standard or inspected on an ongoing basis, get in touch through our contact form with a few details about your building. We will come back to you to arrange a site visit.