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Fire rated timber cladding is a legal requirement on certain UK buildings and a sensible specification choice on many others. Understanding when it is required, what the classifications mean, and how to specify it correctly is essential for architects, developers, and contractors working on projects where facade fire performance is part of the brief.
At Timber Cladding Specialists, we supply factory fire-treated timber cladding certified to Euroclass B-s1,d0 and UK Class 0 standards, across all main species and profiles. Full certification documentation is provided as standard with every order. We are FSC and PEFC certified and hold awards from the Build Architecture Awards 2021 and the London & South East Prestige Awards 2022.
The requirement for fire rated cladding is governed by Approved Document B (Fire Safety), most recently updated in 2022. The rules vary depending on building height, use, and proximity to a boundary. The key thresholds to understand are:
For a full guide to when fire rated cladding is legally required on your project, see our detailed article: Do I Need Fire Rated Cladding on My House Extension?
Fire performance applies to the full wall assembly — not just the cladding boards. Cavity barriers, insulation, and detailing all form part of the compliance picture.
B = limited combustibility (reaction to fire class). s1 = minimal smoke production. d0 = no flaming droplets or particles. All three components are independently tested and certified under EN 13501-1. A certificate must state all three — a product showing only "Class B" without the smoke and droplet suffixes is incomplete and should not be accepted as evidence of compliance.
The UK currently operates two fire classification systems in parallel — the European Euroclass system (EN 13501-1) and the older UK BS 476 system. For external timber cladding, Euroclass B-s1,d0 is the primary standard referenced in Approved Document B and required by most Building Control officers and fire engineers. UK Class 0 (BS 476) remains in use and is accepted in many applications, but the two are not directly interchangeable.
For a complete explanation of both systems and how they compare, see our guide: Euroclass B vs Class 0 vs Class 1 — What Do They Actually Mean?
Factory fire treated timber cladding installed as a ventilated rainscreen system — the treatment process does not alter profiles, installation methods, or visual appearance.
All fire retardant treatment we supply is applied in a factory environment using pressure-impregnation. This process forces the retardant solution deep into the cell structure of each board, producing consistent, measurable, and certifiable penetration across every linear metre of cladding supplied.
This is the only treatment method that reliably achieves certified Euroclass B or Class 0 performance. On-site brush or spray application cannot replicate the penetration depth, consistency, or traceability of factory pressure-impregnation and is not accepted by Building Control as evidence of compliance with Approved Document B.
Only factory pressure-impregnated treatment produces a certifiable Euroclass B or Class 0 result. On-site application of fire retardant is not accepted by Building Control as evidence of compliance. Always specify factory-treated boards where fire classification is required — and always request full certification documentation from your supplier at the point of order.
Fire rated timber cladding on a UK residential project — visually identical to standard cladding, installed in exactly the same way.
Factory fire retardant treatment is available across all our main cladding species. The treatment does not change the visual appearance, installation method, or profile dimensions — fire rated boards look and install identically to untreated boards of the same species.
| Factor | Untreated timber | Factory fire-treated timber |
|---|---|---|
| Reaction to fire class | Typically Euroclass D–E | Euroclass B-s1,d0 |
| Smoke production | Higher / unclassified | s1 — minimal smoke |
| Flaming droplets | Not controlled | d0 — none produced |
| UK Class equivalent | Class 3 or lower | Class 0 |
| Certification documentation | None available | ✓ Full certification supplied |
| Visual appearance | Natural timber appearance | Identical — no visible difference |
| Installation method | Standard | Identical — no change required |
| Suitable for buildings over 11m | ✗ Not acceptable | ✓ Acceptable 11–18m |
| Cost premium | — | Typically 10–20% on material cost |
The cost difference between standard and factory fire treated cladding is typically 10–20% on material cost. On most projects where fire performance is relevant, specifying fire treated boards from the outset is the straightforward choice — it removes compliance uncertainty, satisfies Building Control, and adds no complexity to installation. The cost of remedial work if non-compliant cladding reaches site far exceeds the premium.
When writing a cladding specification or tender document that requires fire rated performance, always state the required classification in full. A correctly written specification clause for fire rated timber cladding looks like this:
External timber cladding: factory pressure-impregnated fire retardant treatment to achieve Euroclass B-s1,d0 classification to EN 13501-1 and/or UK Class 0 to BS 476 Parts 6 and 7. Full certification documentation to be provided by the supplier at the point of order, covering species, profile, treatment system, test standard, and classification. On-site applied treatments are not acceptable.
This wording removes ambiguity and ensures that any supplier responding to the specification is quoting on a genuinely compliant product. If you need assistance with specification wording or have a specific Building Control requirement to meet, contact our team and we will advise on the correct approach for your project.
For architects working on projects that require detailed facade specifications, see our cladding detail design service and our guide to timber cladding specification for UK architects.
It depends on your building height and proximity to a boundary. Under Approved Document B (2022), buildings over 11 metres in height must use cladding materials of limited combustibility — Euroclass B-s1,d0 is the standard required for most buildings between 11 and 18 metres. For buildings under 11 metres, fire rated cladding is generally not a legal requirement unless the wall is within 1 metre of a boundary. Always confirm with your Building Control officer for your specific project.
Euroclass B (B-s1,d0) is a European fire classification tested to EN 13501-1, covering flame spread, smoke production, and flaming droplets. Class 0 is a UK classification under BS 476 covering surface spread of flame. The two are broadly comparable but not directly interchangeable. We supply certification for both systems — confirm with your Building Control officer which is required for your project.
We supply fire-retardant treated cladding in all main species including Siberian larch, ThermoWood, Douglas fir, and Nordic spruce. All profiles available in each species can be treated — shadow gap, double shadow gap, rainscreen, tongue and groove, shiplap, and feather edge. Contact our team with your species, profile, and m² requirement and we will confirm availability and lead time.
No. Factory fire retardant treatment does not change the visual appearance of the timber. The treatment penetrates the cell structure of the boards rather than sitting on the surface, so there is no colour change, surface coating, or texture difference. Fire rated boards look and install identically to untreated boards of the same species and profile.
Site-applied fire retardant cannot reliably achieve or certify Euroclass B or Class 0 performance. Factory pressure-impregnation produces consistent, measurable penetration across every board and can be backed by certification documentation. On-site brush or spray application is not accepted by Building Control as evidence of compliance with Approved Document B. Always specify factory-treated boards where fire classification is required.
Send us your required m², timber species, profile, delivery postcode, and classification target. We will advise the right specification and supply full certification documentation with your order. Nationwide delivery in 7–14 days from stock.