Long-term durability of wood fire protection requires knowledge and regular maintenance treatment

The fire protection of wooden facades must remain at the required level throughout the life of the building – around 30–40 years. However, the actual performance of fire protection is not always properly verified and monitored. Nordtreat ensures the performance of its flame retardants by meeting the requirements of standard EN 16755 and a clear maintenance programme.

In Europe, the long-term durability of fire protection in wood structures is verified by proven compliance with the requirements of standard EN 16755. However, the test results are not always sufficient to ensure real fire protection throughout the building's life. Responsible builders and building control authorities need to know the type of fire protection treatment that has passed the test. In addition, the effect of weather exposure on the duration of the fire protection must be taken into account.

There is simply no such thing as maintenance-free fire protection for wooden facades

Nordtreat's Vice President, Technology Mikko Tuominen says there are many misconceptions and therefore risks associated with the long-term durability of wood fire protection. The biggest misconception is whether the fire protection of wood facades, once applied, will last at the required level throughout the life of the building.

"Regardless of the fire protection technology used, years of weathering will always affect both the performance of the fire protection and the appearance of the building. Therefore, promising complete freedom from maintenance is irresponsible."

Mikko Tuominen, Vice President, Technology of Nordtreat

"The requirements of the EN 16755 standard must of course be met, but when it comes to testing based on accelerated weather exposure testing, it cannot fully reflect the actual performance of the fire protection in varying weather conditions over the years. Unfortunately, the actual performance of fire protection is far from always guaranteed," Mikko Tuominen continues.

Weather exposure will inevitably affect the appearance of a wooden facade over time. There is a risk that a wood cladding that has been fire-protected in the past will be painted with a product for appearance reasons, which will weaken the fire protection and at the same time increase the fire load of the wood structure.

Nordtreat's fire protection technology and maintenance program ensure long-term durability

Nordtreat's bio-based NORFLAM fire protection technology allows the translucent flame retardant to be absorbed deeper into the wood material. No other treatments are required as Nordtreat flame retardants can be tinted to any shade.

Nordtreat's NT DECO and NORFLAM FACADE flame retardants for wood cladding passed the EN 16755 standard tests in spring 2024. The prestigious French FCBA Institute of Technology carried out the tests.

Nordtreat performs continuous research and testing on the durability of flame retardant treatments and coatings.

Spruce panels treated with NT DECO meet the requirements of fire class B-s1, d0 (EN13501-1) and pine panels treated with NORFLAM FACADE meet the requirements of fire class C-s1, d0 (EN13501-1).

Nordtreat's flame retardants also have clearly defined maintenance programmes, whereby maintenance treatments with the same product are carried out every 5–10 years depending on the weather exposure of the site. This ensures that the fire protection of the wood facade is maintained at the required level throughout the life of the building.

Many fire protection technologies have long-term durability challenges 

Fire protection technologies used for wood include heat-swelling flame retardants and fire protection technologies based on impregnation chemistry. 

The challenge of heat-swelling flame retardants from a long-term durability perspective is that the product may need to be repainted immediately upon installation, or at the latest at the first maintenance treatment. Painting over the fire protection almost always increases the fire load, so the results of a passed EN 16755 test are no longer valid. In addition, the effectiveness of the flame retardant treatment is reduced over the years by the effects of sun and rain.

"The standard test should be subjected to the surface treatment that the building will actually receive. When the surface of the flame retardant paint starts to look worn over time, subsequent maintenance coatings often only further degrade the performance of the flame retardant."

Mikko Tuominen, Vice President, Technology of Nordtreat

Fire protection of wood based on impregnation chemistry may be a more durable solution than swelling flame retardant paints, but its performance will not last the lifetime of the building. 

"Over time, the surface concentration of the fire-protecting chemical in the wood decreases and the façade starts to look worn. The surface fire class of the impregnated façade no longer meets the fire safety requirements", Mikko Tuominen says.

Natural and accelerated weathering methods assess service intervals for flame-retardant materials.

Note on testing and compliance with the maintenance programme

The most important thing is to know what has been tested and how. Tests according to EN 16755 should be carried out both before and after the weather load. In addition, the product being tested should not be repainted during or shortly after installation. As Nordtreat flame retardants do not require a separate surface treatment, this problem does not exist.

"Our maintenance program guides you in choosing the right maintenance interval depending on the product to be used and the conditions under which the building product will be installed. As a rule, the maintenance treatment is always carried out with the same flame retardant as the original treatment."

Mikko Tuominen, Vice President, Technology of Nordtreat

The EN 16755 standard is being developed to improve the safety of fire protection

As long-term durability of fire protection is an essential issue for the safety of wood construction, Nordtreat is involved in the development of standards in this field and actively participates in the work of CEN (European Committee for Standardization) working groups.

"The requirements of the EU standard on fire protection of facades need to be reassessed. We are involved in the evaluation working group and will propose improvements during 2025", says Mikko Tuominen.