The BurnBlock® fire-retardant treatment enables Lunawood ThermoWood® to be used in buildings that require a fire class B rating. On this page, we’ve gathered the most frequently asked questions and answers about our fire-retardant Lunawood ThermoWood®.


Does Burnblock leach from Thermowood?

No, BurnBlock® is classified as leach-resistant and is certified for use in INT1 (internal dry), INT2 (internal humid), or EXT (exterior) conditions. Timber treated with BurnBlock® has undergone accelerated aging/leaching testing according to EN927-6, which is one of the three test options in the new EN16755 standard. This test, involving both UV exposure and an amount of water equivalent to more than 120 years of rainfall in a Scandinavian capital, demonstrates that the timber maintains its Euro class B rating both before and after the aging test, as documented through ISO5660 tests. The results indicate that the efficacy of BurnBlock® diminishes at a rate comparable to the natural aging and leaching of the wood itself. Documentation is available upon request.

How should BurnBlock fire retardant be maintained?

The BurnBlock FR treatment for timber is, in principle, maintenance-free and protects the wood against the spread of fire. The wood undergoes a high-pressure treatment process, infusing the natural, non-toxic fire retardant deep into the wood’s cellular structure. For most wood species, this treatment is thorough and permeates the entire piece of wood, eliminating the need for additional treatment after the wood has been cut or drilled.

There is salt on the surface of fire protected Lunawood. How to proceed?

Some salt may appear on the surface of fire retardant Lunawood. This does not affect to the performance of the fire resistance. Salt will disappear from the surface due to rainwater but in locations where rainwater does not meet cladding, washing is recommended.

Why the fire retardant treatment is provided only for planed Lunawood products?

To achieve specific fire classifications and obtain the corresponding certificates, Lunawood’s planed profiles (Lunawood Collection) are rigorously tested to meet the requirements outlined in the Declaration of Performance documents. Opting for already tested profiles ensures better availability and quicker lead times.

It’s important to note that planing fire-retardant thermo timber tends to wear out blades quickly. Therefore, we recommend selecting fire-retardant planed products.

Can you provide fire retardant treatment for thermo timber?

Yes. However, planing fire retardant thermo timber is more challenging due to the impregnated BurnBlock. Fire retardant thermo timber does not carry any certification, and therefore, planed profiles should be tested separately.

How long fire retardant Lunawood remain fire safe after installation?

The BurnBlock® fire retardant treatment does not leach from the wood. As a result, its lifespan matches that of the wood into which it is impregnated.

Why do you use BurnBlock® for fire protection?

BurnBlock® impregnation is an ecological, non-toxic solution. It’s a water-based product composed entirely of natural, fully biodegradable substances. Additionally, it’s pH-neutral, non-corrosive, and free from VOC emissions. BurnBlock® is proven to be 100% non-toxic, natural, and devoid of heavy metals. This fire protection method aligns with our commitment to thoroughly sustainable product solutions.

What are the construction principles for fire retardant Lunawood?

The substrate must meet the fire classification of A1 or A2-s1,d0, according to the Declaration of Performance (DoP) documents. Support battens should be either wood in fire class D or aluminium. The cladding should meet a fire classification of B.

For closed structures, a ventilation gap is required, i.e., for tongue & groove products, as per the Lunawood installation guide for facades. Open constructions must be tested and approved separately. Installation and fastening with nails and screws should be done in accordance with Lunawood’s instructions.

Always consult your local fire safety authorities.


How to paint fire retardant Lunawood?

Painting must be done by a CE-certified painter e.g., not at the building site. CE-certified painting process enables maintaining fire class after industrial painting. It is important to note that anything you add to the wood surface could change the fire rating and thus solution needs to be tested separately.

How to maintain Lunawood that has been impregnated with BurnBlock and treated with SiOO:X?

Maintenance treatment can be performed 5-8 years after installation, depending on the visual appearance of the cladding. If the cladding has weathered nicely and evenly, maintenance is not needed or can be done until after 15 years.

SiOO:X light-grey and mid-grey are pre-greyed solutions; thus, the pigment will eventually fade away due to the sun’s UV radiation, leaving the wood naturally greyed beneath the pigment.

SiOO:X does not affect the fire resistance.

How to maintain Lunawood that has been impregnated with BurnBlock and treated with Sherwin-Williams?

Burnblock treated Lunawood which is surface treated with Sherwin Williams black paint require the first maintenance during 12 months after installation. Reapplication after 6-8 years depending location and climatic conditions.

Suitable for outdoor and indoor applications

Fire retardant Lunawood product range

Lunawood offers several cladding products impregnated with BurnBlock® fire protection. Lunawood ThermoWood® treated with BurnBlock® is suitable for outdoor and indoor applications, including wall and ceiling panels, offering reliable fire protection. We now also provide factory-painted options in light grey, mid-grey, and black.
Discover the entire product range on our website.

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