Fire performance ratings for external timber: What you need to know

Is timber highly flammable? That depends on the species you are using. Most timbers used in construction, for example Oak, actually are not more flammable than other materials, thanks to their high density and slow burn rate. Getting the timber actually to catch fire often takes another source of fuel (which you can see in action when trying to light a fire in your wood burner; kindling and firelighters are still needed!). 

That being said, following fire performance regulations when installing external timber is still essential. To ensure legal compliance and maintain the safety of your building, we have put together a no-nonsense guide to timber fire performance ratings. Let’s dive straight into it.

Upgrading Timber to Euroclass Ratings

When specifying and treating timber, the UK uses Euroclass ratings. Untreated timber typically has a Euroclass rating of around D or E, meaning that it is naturally combustible and will contribute a medium amount of fuel to a fire. It is not the most flammable material by a long shot, but it also will not stop the flames from spreading.

To improve the fire resistance of your external timber (such as cladding or fencing), the wood can be treated with a fire-retardant. This will help your timber reach a Euroclass B or C.

It is important to note that you cannot make timber reach Euroclass A, which is the rating for non-combustible materials. Even with treatments, timber is still an organic material and has combustible traits, which makes this category impossible to achieve.

Most of the common cladding species we offer can be treated to Euro Class B. Though a few tropical hardwoods – e.g. Ipe and Jatoba – are too dense for treatment, staples such as Cedar, Larch, Douglas Fir and ThermoWood can all be supplied with a Euro Class B rating.

Fire Performance Rating Requirements

In the UK, the fire performance required for external timber depends heavily on building height, use and location of the timber. Approved Document B, which is the cornerstone of UK fire safety guidance, outlines where enhanced fire performance is mandatory and where it is simply recommended. Key points to note include:

• Exterior timber within 1 metre of the building should be rated to Euroclass B.
• Higher-risk buildings which are over 18 metres (such as multi-storey residential blocks) demand more stringent fire safety, meaning that timber cladding usually is not allowed.
• Where external walls form part of the escape routes, fire resistance will be a significant consideration.
• Even when regulations do not explicitly require a Euroclass B product, insurers, warranty providers and local building control officers increasingly expect it as a minimum for timber cladding.
  

Put simply: the higher the building and the higher the risk, the higher the Euroclass rating you will need to achieve for your external timber.

Testing and Proving Compliance

Before use, your timber must be tested in alignment with the Construction Products Regulation (CPR). This means that:

• Fire testing must be undertaken by a recognised body
• The classified rating must be backed by a valid fire classification report
• The timber must be produced under a certified Factory Production Control (FPC) system
• A Declaration of Performance (DoP) can be issued for any construction timber

The good news is that EcoChoice can help you achieve the correct fire performance ratings for your timber, making compliance a whole lot easier. Our team stays up to date with industry requirements and will be happy to source Euroclass B or C timber for your construction project and advise you on how best to meet regulatory requirements.

Speak to Our Timber Experts

Meeting the UK’s fire performance rating requirements is a must. If you are looking for a fire-retardant-treated timber for your next project, you are in the right place. Let us know what you need, and we will find the right timber products to tick all your boxes.

Chat with our team today.