Fire retardant impregnation vs paint for wood: Which system to choose?

Fire protection of wooden structures is not only about achieving a required fire class. The right solution also depends on the desired appearance, substrate condition, application process, maintenance logic, and exposure environment.

Transparent fire-retardant impregnation and transparent intumescent coatings are options for preserving the natural appearance of wood; opaque fire-retardant paint systems provide a covering finish. The choice depends on the required fire class, substrate, desired appearance, and a documented, tested system. Impregnation requires an absorbent surface, and any existing coating must be assessed before specifying a fire-retardant coating system.

Both systems can have a valid role in fire-safe timber construction. The correct choice depends on the project objective.

01What is the difference between an impregnating agent and fire-retardant paint?

A fire-retardant impregnating agent is designed to be absorbed into the wood's structure. Its purpose is to improve the fire behavior of the wood while preserving as much of its natural appearance as possible.

The fire-retardant paint system works as a surface layer. It usually consists of several layers, such as a fire-retardant primer and topcoat. Opaque paint systems cover the wood grain, resulting in a painted surface. Transparent intumescent coatings also exist. Suitability depends on the system and substrate.

In simple terms, an impregnating agent is suitable for visible absorbent natural wood, and opaque fire-retardant paint is for situations where the wood is supposed to have a covering painted finish. Transparent intumescent coatings are another option, depending on the system and substrate.

02SPFR100 vs. fire-retardant paint: key differences

03When to choose SPFR100?

SPFR100 is particularly suitable for projects that aim to combine fire safety with the natural appearance of wood. It is a transparent, water-based impregnating agent designed for a broad range of absorbent wood and wood-based materials, including façades, cladding boards, structural timber, plywood, CLT panels, and other visible timber applications. The choice between SPFR100, transparent intumescent coatings, and opaque fire-retardant paint systems depends on the required fire class, substrate, desired appearance, and a documented, tested system matched to the intended use.

A surface treated with SPFR100 retains the wood's natural appearance and does not require an additional finishing layer. This is a significant advantage in architectural solutions where the texture and material sensation of the wood are part of the end result.

SPFR100 is a suitable choice if:

• The goal is to achieve reaction-to-fire class B-s1,d0.
• The wood must remain visually natural.
• The surface is absorbent and is not covered with a pore-sealing lacquer, paint, or oil.
• The solution must be suitable for indoor or outdoor conditions.
• It is important to have a VOC-free, formaldehyde-free, halogen-free, and pH-neutral composition.
• You want to avoid a multi-layered paint system.

The certified total application is 240 g/m² (approx. 210 ml/m²); practical total consumption is 210–250 ml/m² depending on conditions and current instructions. Under normal conditions, the drying time is 24–48 hours. Full fire-retardant performance develops within 5–7 days after treatment.

04When to choose a fire-retardant paint system?

An opaque fire-retardant paint system may be a sensible choice if the project calls for a covering painted surface. Transparent intumescent coatings are also an option when the wood grain should remain visible. The choice depends on the required fire class, substrate, desired appearance, and a documented, tested system.

An existing coating may prevent impregnation, but does not automatically make a fire-retardant paint or transparent intumescent coating suitable. The existing coating must be assessed for compatibility with the documented, tested system. SPFR100 is generally not suitable for surfaces that are covered with pore-sealing coatings, such as lacquers, paints, or oils.

A fire-retardant paint system may be a suitable choice if:

• The end result must be a painted surface.
• The wood's natural appearance is not important.
• Any existing coating has been assessed as compatible with the documented, tested system.
• The project requires a specific color tone or covering finish.
• The client has taken into account a multi-layered system and its maintenance.

05Work process and maintenance

SPFR100 is applied in at least two coats, with a minimum of 60 minutes between coats. The drying time under normal conditions is 24–48 hours.

Fire-retardant paint systems usually require several interrelated layers. Therefore, in addition to the cost of the material, you need to consider the stages of work, drying times, control of layer thickness, and subsequent maintenance.

SPFR100 maintenance usually requires just one maintenance layer with a quantity of 120–140 ml/m2 on a clean, dry surface when the yearly inspection shows it is needed; see the maintenance guide. If the treated surface gets mechanically damaged, the damaged or cut areas need to be re-treated.

For paint systems, maintenance depends on the condition of the entire system. If the top layer is damaged or peels off, it needs to be assessed whether only the visible paint layer is affected or whether the fire-protective base layer is as well.

06Summary

SPFR100 and fire-retardant paints fulfill the same general purpose but are suitable for different situations.

If the goal is to preserve the natural appearance of the wood and achieve reaction-to-fire class B-s1,d0, SPFR100 or a transparent intumescent coating may be suitable, depending on the substrate and a documented, tested system. It is well-suited for visible wooden surfaces such as façades, cladding boards, and other absorbent wood-based applications. For CLT panels and other wood-based materials, SPFR100 may be a suitable solution, but the required reaction-to-fire classification, substrate, and project-specific documentation should be confirmed before specification.

If the goal is a covering painted surface, an opaque fire-retardant paint system may be more suitable. If the base surface does not allow impregnation, an opaque or transparent intumescent coating may be an option, but any existing coating must be assessed for compatibility with the documented, tested system.

The right choice always depends on the project: the base surface, fire safety requirements, desired appearance, usage environment, and maintenance logic.

07FAQs

Is fire-retardant impregnation better than fire-retardant paint?
Neither is automatically better. Impregnation and transparent intumescent coatings can preserve the wood's natural appearance, while opaque fire-retardant paint provides a covering finish. The choice depends on the required fire class, substrate, desired appearance, and a documented, tested system.

Can fire-retardant impregnation replace fire-retardant paint?
Not always. Impregnation requires an absorbent surface, while transparent intumescent coatings and opaque fire-retardant paint systems form surface layers. Substitution depends on the required fire class, substrate, desired appearance, and a documented, tested system. Any existing coating must be assessed; it does not automatically make a fire-retardant coating suitable.

Can SPFR100 be used on painted wood?
SPFR100 is designed for absorbent wood surfaces. Existing film-forming coatings, such as paints, lacquers, or oils, can block absorption, so previously coated surfaces should be assessed before treatment. In many cases, the coating must be removed. An opaque fire-retardant paint or transparent intumescent coating may be an alternative only after assessment of the existing coating and confirmation of a documented, tested system for the required fire class, substrate, and desired appearance.

Does SPFR100 preserve the natural look of wood?
Yes. SPFR100 is transparent and is designed to preserve the natural appearance of wood.

Is SPFR100 certified to B-s1,d0?
Yes, under the certified scope defined in the classification report K16/2024 and certificate ET-0388-24. The current certificate ET-0388-24 was first issued on 14 February 2024 and remains valid until 13 February 2029, provided that the technical description, manufacturing conditions and factory production control are not significantly modified.

Want to know whether SPFR100 or a paint system is better suited to your project? Contact us, and we will help you choose a technically suitable solution.

See a full side-by-side comparison: impregnation vs intumescent paint vs pressure treatment →