TEE-Logo

TimberEngineeringEurope

You are here: Articles & Advice - Timber Frame Info - Fire

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 universally accepted.

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".


Go Top


Logo

Many new ecological materials are available to extend the fire rating internally and externally of ANY type of building.



©Timber Engineering Europe  -  Design by Ytrion