Choosing your cladding
Fire retardant cladding: species, colours and finishes
A fire rating should not mean a compromise on design. You can choose from a range of species, profiles and finishes, as long as the combination is covered by the certificate.
This page covers the common choices and the points to check. What a treated board achieves depends on its species, thickness, treatment and tested end use, so use this as a starting point and ask for the certificate for your combination.
Choosing a species
- Western red cedar: lightweight and stable, with a classic look.
- Larch: a durable, cost-effective choice with a golden tone.
- Spruce and pine: economical options for larger areas, often painted.
- Thermally modified timber: dark, stable and chemical-free before treatment.
Species absorb treatment differently. Dense timbers can be harder to impregnate, and some systems are not suitable for modified timbers, so the choice of species and the choice of treatment should be made together. Our treatment systems page notes where a system has known limits.
Impregnated or surface-applied
Impregnated systems carry the retardant into the timber, while surface-applied systems rely on a coating. This matters for finishing and for cut ends. Where boards are cut on site, the guidance for the specific system will say how to treat exposed ends.
Surface-applied coatings also need maintenance, because wear and weathering can affect the layer that provides the protection. Ask the supplier for the maintenance and re-treatment advice that goes with the certificate.
Finish options
| Finish | Look | Notes |
|---|---|---|
| Natural / clear | Shows grain and colour | Check compatibility with the treatment |
| Pigmented stain | Adds colour, shows grain | Needs periodic maintenance |
| Painted | Solid colour, many options | Factory finishing can give consistent quality |
| Weathered | Silver-grey over time | Lowest maintenance; colour may vary |
Use only finishes approved for the treatment system, so the fire classification stays valid. Always ask which coatings the report covers, because a certificate usually names the finish it was tested with. If a certificate was issued for treated but unfinished boards, a different finish may need separate confirmation.
Profiles
Common profiles include shadow gap, tongue and groove, rhombus, board-on-board and open-joint rainscreen. Certification may differ between profiles, so confirm the profile on the certificate. See our timber profiles page for dimensions.
Open-joint and slatted designs also affect the cavity behind the boards, so discuss cavity barriers with your designer. Thickness matters too: a thicker board of the same species and treatment may not carry the same classification as a thinner one, so match the thickness to the report.
Ordering and samples
Colour and grain can look different on a screen, so we offer free samples. Shop prices include VAT and UK delivery. Many items ship next day, while bespoke and painted orders usually take 5 to 7 working days, and treated orders need extra time for treatment, drying and finishing.
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.