There are three common ways to give timber a reaction-to-fire classification. They differ mainly in whether they leave the wood visible, how they are applied, which substrates they suit, and how they are maintained. This is a neutral guide to help choose the right approach - the best option depends on the project, not on marketing.
| Criterion | Transparent impregnation (e.g. SPFR100) |
Intumescent paint | Pressure treatment |
|---|---|---|---|
| Appearance | Wood stays visible; no surface film | Opaque coating; covers the grain | Wood stays visible; minimal film |
| How it works | Penetrates into absorbent wood | Swells into a char layer in fire | Impregnated under industrial pressure |
| Application | Brush, roller or spray; on site or in factory | Multi-coat system; often primer + topcoat | Factory only; buy pre-treated timber |
| Best for | Natural, visible timber where appearance matters | Projects where a painted finish is acceptable | New timber specified pre-treated from the mill |
| Substrate needs | Absorbent, unsealed wood | Most surfaces (forms a coating) | Species-specific; done before installation |
| Maintenance | Exterior: inspect/renew every 5-10 years | Recoat per system; film can wear | Generally long-term; product-specific |
Choose transparent impregnation when...
the natural look of the wood must be preserved (visible facades, interior cladding, exposed timber), you want on-site or factory application, and you are working with absorbent, unsealed timber. SPFR100 is this type of product.
Choose intumescent paint when...
a painted, opaque finish is acceptable or desired, or the substrate is not suitable for penetrating impregnation. The wood grain is covered.
Choose pressure treatment when...
timber can be specified pre-treated from the mill, a minimal surface film is wanted, and the species has documented pressure-treatment durability. Treatment happens before installation.
A EuroClass such as B-s1,d0 is only valid within the exact tested configuration - wood species, thickness, application amount, coating and end-use. Do not select a product on the label class alone; request the classification report matching your project. B-s1,d0 is a reaction-to-fire class (limited fire contribution, low smoke, no flaming droplets); it does not by itself provide 30- or 60-minute structural fire resistance.
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