Intumescent wood varnish 1L, 5L and 20L – Vi Bois

To achieve classification B-s1,d0, the substrate must be coated at a rate of 200 g/m². Here is the coverage according to the packaging: B-s1,d0 classification?

Here are some simple guidelines for estimating the required volume:

• • 12 m² : allow 2 liters
  • 30 m² : allow 5 liters
  • 60 m² : allow 10 liters

Intumescent varnish may leave a slight whitish film, especially if too thick a layer is applied.

Yes, the B-s1,d0 classification corresponds to a reaction to fire performance according to the Euroclass and is recognized as equivalent to the French M1 standard for this type of application.

• B: Limited contribution to the development of the fire
• s1: low smoke emission
• d0: absence of flaming droplets

To delve deeper into this point, see the fire safety standard and associated classifications.

Intumescent wood varnish is designed to protect interior wood surfaces against fire while preserving the visible appearance of the material. It is particularly suitable for projects where fire safety must be integrated without obscuring the wood, especially on solid wood, wood panels, wall coverings, ceilings, and decorative elements.

When exposed to significant heat, the varnish swells and forms an insulating carbon foam. This reaction slows the temperature rise of the substrate and limits the spread of flames.

• Fire protection of interior wooden supports
• The appearance of the substrate is preserved, although a slight whitish haze may remain.
• Application suitable for visible installations
• Suitable for use in public buildings, shops, hotels, restaurants, offices and exhibition spaces

To compare this approach with other wood solutions, you can consult
our guide on wood fire protection.

Intumescent varnish is particularly suitable when the substrate requires fire protection while maintaining a visible and protected wood appearance. It is appropriate for interior surfaces where a surface treatment is more suitable than impregnation into the material.

It provides fire protection with a simple application logic, in a single layer, while meeting the needs of projects where the visual finish of the wood remains important.

• The wood remains visible after treatment
• The product is applied in a single layer
• The mechanism relies on an intumescent reaction in the presence of heat
• The system is suitable for solid wood and wood panels indoors.

For raw resinous wood, a different treatment approach is recommended. Discover our wood fire retardant.

The application must be regular and controlled to guarantee fire performance. The product can be applied by spray gun or roller, provided that the specified weight is strictly adhered to and the uniformity of the application is checked.

Spray gun application is recommended for an even coating. Roller application is still possible if the basis weight is precisely controlled

• Prepare the surface properly before application
• Apply evenly over the entire surface
• Respect the weight of 200 g/m²
• Use a spray gun for better film consistency.
• Controlling multiple areas in the event of a major construction project

Reference point for calculating wet thickness

For projects requiring more precise application control, wet film monitoring can be useful.

To ensure the treatment’s effectiveness, the substrate must meet several conditions before application. A poorly prepared substrate can reduce adhesion, film uniformity, and the desired performance.

• Raw, clean and dry wood
• Humidity below 18%
• Minimum thickness: 8 mm
• Application temperature above 5°C
• Absence of previous varnish, paint or coating

The solution is different for surfaces that have already been coated. If you are working with other types of wood or in other contexts, you can consult our range of wood fire retardants.

Under the effect of heat, the varnish swells and forms an insulating foam, also called carbon meringue. This thermal barrier protects the wood surface by slowing its temperature rise and limiting the spread of flames.

This mechanism allows the support to be protected without covering the wood with an opaque coating, making it a suitable solution for interior projects where the appearance of the material matters as much as fire performance.

The finish is not mandatory to obtain the fire classification, provided that the intumescent varnish is applied at the correct weight.

However, it can be useful for protecting the active layer on surfaces exposed to wear, friction, or ambient humidity. The choice of finish therefore depends on the actual use of the surface.

• Finish not required for fire classification
• Useful finish for areas exposed to wear and tear
• Choices should be adapted according to the context of use.

To see related references, you can consult
the intumescent wood varnish finish.

The following technical data makes it easier to anticipate the implementation of the product on site.

For projects requiring supervised application or on-site support, you can consult our wood treatment service

In case of overapplication, particularly if too much product is applied to the same area, the material may appear whitish or develop a more visible haze after drying. To preserve the aesthetic appearance of the surface, it is important to adhere to the recommended dosage of 200 g/m² and to distribute the product evenly.

This intumescent varnish can be used on interior design projects on wood substrates, particularly in spaces subject to fire safety requirements.

Several key points can help improve the consistency of results and ensure the desired performance:

• Check the condition of the surface before application
• Respect the weight of 200 g/m²
• For a more even finish, use a spray gun.
• Choose a compatible finish if the surface is exposed to wear and tear.
• Keep the technical documents and the fire classification report.

To further your research, you can also read our content on the durability of a fire-retardant treatment and discover all of Alfaflor’s fire-resistant treatments.