Fire Resistant Doors
Most people are happy to have their fire doors installed, without needing to understand how the doors and their frames are constructed, however the combination of materials that contribute to the door set’s ability to withstand the extreme pressures of smoke and flames are an impressive mix of resources.
Fire doors are likely to be made up of a mixture of glazed sections, steel, timber, vermiculite, aluminium and gypsum, all of which are designed to hold back flames or resist heat. In combination, they make up an effective form of protection, ensuring that business- and home-owners can feel confident of their fire doors’ ability to keep them, and their property, safe. Every aspect of the door set must be suitable for the job, because a dedicated fire door with the wrong frame, letter box or glass will fail to offer adequate security.
The outer layer of a fire door is the veneer surface, which is what gives a fire door its outward appearance. Below that is the substrate, under which is the essential fire resistant core. Within the core are the internal stiles and rails.
It is possible to still obtain solid timber fire doors, however more modern door options are available which make a door considerably lighter and reduce the cost while still offering the same protection. A further benefit with newer doors is that manufacturers are able to source the raw materials in a more sustainable manner, and these doors can be made to fit in with a building’s surroundings, using different available finishes. Doors with a wood composite core can be covered with a laminate or moulded skin which will be designed to suit the rest of the interior of the building. These can be built to suit anything from a historic building to a brand new apartment complex.
Because every aspect of a fire door set must be able to resist fire and smoke, the glazing components must also meet these standards. Normal glass cracks quickly when exposed to heat, which makes it ineffective at containing a fire to a single, isolated compartment within a building. Fire resistant glass, on the other hand, is built to withstand heat for a minimum of one hour. The materials which attach the glass to the frame must also be able to tolerate this degree of heat. Smaller panes of glass tend to take longer to soften and collapse than larger ones, and the glazing can be fitted to allow intumescent seals to expand in the event of extreme heat.
The construction of the fire door frames must also be carefully planned to ensure that they can play their vitally important role in the prevention of fires spreading. For an FD30 fire door, which will withhold heat, smoke and flames for a minimum of half an hour, the wood normally has to be Redwood which is a minimum of 30mm thick. MDF is occasionally allowed as an alternative. The type and density of the wood must match what is specified in the installation instructions, and the dimensions have to be carefully measured.
