Regulations
Timber cladding and fire safety regulations in the UK
Fire safety rules for external walls are different in England, Scotland, Wales and Northern Ireland, and have changed in recent years. This page gives an overview of the factors that matter, so you know what to ask. It is not legal or professional advice.
The details below are a general outline. Always check the current version of Approved Document B and speak to your local Building Control, or a fire engineer, before you specify.
What affects the requirement
- Building type and use: dwellings, flats, offices, schools, healthcare and other uses have different rules.
- Building height: taller buildings face stricter limits on combustible materials.
- Distance to the boundary: walls close to a boundary face limits on surface flame spread.
- Which nation the building is in.
- The wall build-up, including cavities, insulation and barriers.
Distance to the boundary
Walls close to a relevant boundary are generally required to limit the spread of fire to neighbouring property. Approved Document B has long used a distance of 1 m from the boundary as a key point, with tighter limits on the surface of the wall closer than that. The exact classes and exceptions depend on the building type and size, so check the current tables.
Untreated timber cladding may be acceptable in limited areas or at greater distances, while fire retardant treated cladding can allow timber on elevations that would otherwise be restricted. Older guidance expressed this as Class 0 or Class 1 under BS 476, and current guidance generally uses Euroclasses.
Taller buildings and the 18 m rule
In England, the 2018 amendment to the Building Regulations banned combustible materials in the external walls of relevant buildings 18 m and above in height. Relevant buildings include blocks of flats and certain other residential uses, such as hospitals and student accommodation. For these, materials generally have to reach Class A2-s1,d0 or better, which timber cladding, treated or not, does not.
Thresholds, definitions and exemptions have changed and may change again, so confirm the current rules. Timber cladding can still be used on many low-rise buildings and on parts of taller ones where permitted.
Scotland, Wales and Northern Ireland
The rules are not identical across the UK. Scotland uses its own Technical Handbooks, Wales has its own guidance and Northern Ireland has Technical Booklets. Height thresholds and building categories can differ from England, so do not assume that an English answer applies elsewhere. Check the guidance for the nation where the building stands.
Cavity barriers and fire stopping
Ventilated cladding creates a cavity behind the boards. Cavity barriers and fire stopping limit fire and smoke spread through it and are required at specified locations. Intumescent-backed barriers are often used where an open-joint profile is specified, to prevent a gap from compromising the barrier.
The class of the cladding is only part of the picture. The membrane, insulation and the wider wall build-up are also considered.
Your next steps
- Identify the nation and the building category.
- Ask Building Control or your fire engineer for the required class and any restrictions.
- Choose timber, profile and treatment that meet it, with the certificate to prove it.
- Design the cavity barriers and fire stopping.
- Keep the documents for handover.
Shop and specify
Frequently asked questions
Talk to our timber team
Tell us about your project and we will recommend the right species, profile, finish and fire performance. Free samples are available, and we can quote for bespoke milling.