Fire Doors
Introduction to Fire Doors
Fire doors are a legal requirement in almost all commercial buildings, most accommodation premises – including blocks of flats, sheltered accommodation, houses of multiple occupancy, etc. – and even some larger owner-occupied houses. But what are they? Why are they important?
Compartmentation & Passive Fire Protection
Firstly, a basic understanding of “compartmentation” is required to understand the purpose of fire doors. Compartmentation is the idea behind passive fire protection, the process of stopping an active fire from spreading further. It is a structural design principle requiring that areas of a building be sealed off from each other by fire-resistant materials so that if a fire occurs in one area it cannot, or will take a long time to, spread to other areas. This is for the purpose of protecting escape routes for the occupants of other areas and to hopefully prevent the entire premises burning down.
What is a Fire Door?
As you can imagine, a normal door being used in a fire-resistant wall at the boundary of a “fire compartment” would easily allow fire to spread into other areas of the building. Fire doors, on the other hand, when closed, will stop the spread of fire. They are constructed from materials designed to resist fire for a certain amount of time, so it is usually not possible to “convert” a normal door into a fire door. The most common types are wooden fire doors with either 30 or 60 minute fire resistance, though specialist doors capable of resisting fire for over 4 hours may be necessary in certain situations.
When walking around buildings you will most likely see fire doors with signs in the form of a blue circle containing white text, most commonly stating “fire door keep shut.” These signs are mandatory and identify fire doors within a building. Another common indicator is the existence of an fire door closer which is mandatory on most fire doors.
Trimming Fire Doors
One of the most common queries about fire doors is how much material can be trimmed off the sides of a fire door. This may be for the purposes of fitting a new fire door into an existing fire-resistant.
The short answer is: there is no general, recommended, or mandatory amount on a fire door that can be trimmed.
Traditional, solid wood fire doors used to be tolerant of significant material removal, however, modern fire door design uses lightweight materials with higher fire resistance at the edges of the door and lesser resistance within the core, so removing the high resistance edges (eg lippings) seriously impacts on the fire resistance of fire doors.
Accurate trimming information can only be provided by the manufacturer on a case-by-case basis. Guidelines for each door’s allowances can be found in the data provided by the manufacturer.
Trimming too much material from a fire door will result in a loss of integrity as the core materials may have been compromised. This means that the fire door’s test certificate may be void because the door has been altered outside the scope of its certification and its performance may be affected, rendering the door illegal.
Fire Door Construction
Wooden fire doors are typically around 44mm (FD30) or 54mm (FD60) thick. Internally they are constructed either from a solid core – usually particleboard, chipboard, or timber – or with a hollow core design. Some fire doors use timber framing around the core, others have a hardwood lipping on two or three sides to create sufficient fire resistance and to allow for minor trimming, and some may have a plywood or MDF sheet glued directly to the core without any frame or lipping.
Regardless of the construction of a fire door, most manufacturers provide a wide range of finishes such as primed, painted or wood-effect veneers. These do not provide any fire resistance to the finished door set, though may be considered as part of the construction for the purposes of tests and certification, so you should confirm with the manufacturer before altering the surface of your fire doors.
Some manufacturers offer options of fireproof glazing (windows) or raised and fielded panels. Existing fire doors must not be altered by adding glazing or panels without consulting the manufacturer and, if permitted, it is highly recommended that the work is only carried out by a competent person.
Essential Items & Fire Door Furniture
Any component of a fire door other than the actual door leaf and its frame will fall under the term “fire door hardware” or “fire door furniture,” including hinges and edge guards, and some pieces of furniture are considered “essential items” as all mandatory fire doors must have them. The essential items are hinges, appropriate signage, and either a lock or an automatic fire door closer. Note that a closer can only be omitted if the door has a lock and is intended to be locked at all times – such as a cleaner’s cupboard, server room, etc.
All fire door components, furniture, and aesthetic components which penetrate the surface of the door – or wrap around the door from one side to the other – must be fire rated. This includes the hinges attaching it to the frame, the intumescent seals around the edges, the door closer fitted at the top, and almost everything else attached to the door.
It is, for example, no use having an FD60 fire door fitted with a standard lock – while normal stainless steel can survive a typical office fire, the internal components of a standard lock may be made of other materials with lower melting points.
Intumescent Seals & Smoke Protection
Intumescent materials are designed to swell and enlarge when exposed to heat, thereby sealing any gaps in and around a fire door, blocking the path of the fire. Intumescent fire seals are required around the edges of the door – though can be applied to the frame instead.
Strips of intumescent material may also be required between the frame and hinge as well as between the hinge and the door – likewise behind other hardware such as locks and closers. Intumescent sealant, often an expanding foam, is also used between the frame and wall or to fill out other gaps, such as cut-outs for security viewers. The intumescent seals around the edges of the door or frame will often also have an integrated smoke brush to stop the spread of smoke (cold smoke seals).
Smoke spreads much quicker than fire and will often not provide sufficient heat to activate intumescent seals, allowing it to flow around the door within its frame. This cannot always be avoided – some doors have ventilation grilles in them which will be protected by intumescent but are specifically designed to facilitate the flow of air until exposed to enough heat to trigger the intumescent. However, fire doors leading to escape routes or fire doors in buildings with stay-put policy might require cold smoke seals, in which case intumescent air transfer grilles are not suitable. The fire risk assessment carried out should identify the type of fire door and seal required.
Certification of Tradesmen
Another question frequently received is whether or not certified tradesmen must be employed to work on a fire door, whether for installation, modification, or maintenance.
The short answer is: no, certification is not required for a person to work on a fire door. However, we recommend that only competent craftsmen are used for these works.
Legislation, building regulations, and the relevant Standards all require – if anything – that the worker be competent for the job they are doing. The HSE defines competence as “the combination of training, skills, experience and knowledge that a person has and their ability to apply them to perform a task safely.” While this definition does point to training, it does not specify the training be formal or result in any certification or qualification.
In the eyes of the law, the premises’ Responsible Person must ensure the competence of any workers to the best of their ability. This can involve demanding that only qualified and certified workers are employed, but it can also simply be picking a local carpentry company because they are the only one with customer testimonials on their website which relate to work on fire doors. As long as the Responsible Person can prove – in court, to their insurers, etc. – that they have ascertained competence then the worker becomes liable for any issues with the work.