Are timber fire doors the right choice for every environment?
By Paul Shadbolt, MAFDI
London Fire Door Consultants
A colleague recently sought my view on the suitability of timber fire door assemblies for use within a car park environment, and my response was broadly along the following Lines.
Timber fire doors are perfectly capable of achieving the required fire rating when correctly manufactured, installed and maintained. The challenge arises when they are placed in environments very different from those assumed in their design.
An unheated, uncontrolled car park is rarely a stable environment. Temperature fluctuates, ambient relative humidity rises and falls, and condensation is common. In some cases, the faces and edges of the door assembly are at risk from contamination from road salts, vehicle exhaust, moisture, and occasional water ingress.
Timber is hygroscopic and, even when kiln-dried to the equilibrium moisture content expected for internal conditions, it will continue to absorb and release moisture in response to temperature and humidity changes. Over time, repeated cycles can result in structural movement with swelling, shrinkage, bowing or frame distortion becoming manifest.
In many applications, this is a simple maintenance issue but, for a fire-resistant door assembly, where dimensional tolerances and reliable self-closing performance are fundamental to maintaining integrity and smoke control, changes in gaps, seal contact, and Hardware performance can have compliance implications.
Moisture exposure can also affect key components of the door assembly: intumescent seals, smoke seals and ironmongery are all influenced to varying degrees by damp or aggressive conditions. Again, this does not mean inevitable failure — but it does increase long-term risk and maintenance dependency.
By contrast, external grade steel fire door assemblies are inherently more stable in environments where temperature and humidity are not controlled. Steel does not respond to moisture in the same way as timber, and appropriately specified systems, complete with use of the correct finish, offer predictable dimensional stability and durability in harsher Settings.
The real issue is not whether a timber fire door can pass a fire test, it is whether the material selection reflects the environmental demands of the location over the life of the Building.
It is clear, therefore, that when selecting fire door assemblies, it is important to consider their context as well as their compliance.
