Timber Engineering Europe
FIRE RESISTANCE IN TIMBER TRAME BUILDINGS
(Also see article in NEWSBOX - FIRE RESISTANCE IN TIMBER FRAME CONSTRUCTION)
It should be remembered that ALL buildings burn and all buildings of any description MUST
comply with certain fire
prevention codes. Timber Frame complies with most codes and regulations worldwide, and our kits are based on Approved Doc B
(UK Building Regulations) which incidentally are the most stringent in the world. All kits and components also comply
with the Eurocode 5 under EN1995-1-2 which is a fairly new code and deals with the subject in a systematic way.
Timber deterioration in fire is measured by "char rate" and believe it or not, timber is the safest material commonly used
material in construction.
Reinforced Concrete, Masonry and Steel are the main methods of traditional construction and Concrete/Masonry suffers
from "Explosive Spalling" in fire, due to the moisture always trapped, turning to steam and causing the spall.
It is also claimed that differential expansion between the rebar and concrete weakens any load-bearing element quite quickly.
Steel will buckle and twist causing collapse. Timber on the other hand, has a known char rate and the type of timber we use
is noted at 0.65 mm/min on the exposed face, plus a small factor to account for heat damage. Methods of calculation are
There are several ways of dealing with fire prevention and protection and one such method we use in
Timber Engineering is:
Protection by Over-sizing
Timber burns from the external surfaces only. After ignition of the timber, there will be a charred region which acts as an
insulator and tends to protect the wood fibres in the centre of the beam. With time, some of the timber cross-section is lost.
However, the remaining timber can and does have structural strength and stiffness. So, by calculating the dead and imposed
loadings of a subject building we can accurately specify the minimum timber dimensions required to give 30 minutes of char
before any collapse is likely. If we then increase the timber sizes we automatically extend the period of fire protection
considerably, and this is the norm in the industry.
Another way we achieve fire protection is:
Protection by cladding
The interior fire integrity of a building is dictated by using Internal Surface Linings (ISL'S) that must meet minimum
Class 0 UK (Euroclass B) and Class 1 UK (Euroclass C). The simple expedients of cladding the timber frame internally with
Plasterboard 12.5mm thick affords 30 minutes fire protection, before the timber studs are reached - then the over-sizing
margins kick in. Again, simply adding a second layer of plasterboard over the first doubles the protection to 1 hour.
Specialist board is readily available that will increase the resistance to even longer periods of protection time although
budget is the governing factor in most cases.
A third way - and for external cladding
Protection by Intumescent Applications
Externally clad buildings are usually protected by the application of "Thermocoating". A thermocoat product will always have
been tested to meet the standards laid down exactly as the Cladding above. A minimum standard is 30 minutes fire protection
although with some two-pack lacquers up to 120mins is achievable. There are also several water-borne applications that can
be applied by those who wish to embrace more ecological materials.
It should be remembered that the vast majority of house-fires start internally as a result of occupant carelessness and it
is the CONTENTS of the house that burn easily. Smoke is the killer and if a person has not exited the building before the
applied fire protection barriers are breached, it is unlikely that he or she will do, alive. With this in mind, the
length of fire protection applied internally is of little consequence.
TRADA and BRE fire safety research concluded that: "Timber frame performs as well as other construction in fire and life
safety is at no greater risk"