FIRE PROTECTION OF CLT – CROSS-LAMINATED TIMBER

1. WHY FIRE-PROTECT CLT

CLT elements have very good and predictable fire resistance properties. To fulfil building code requirements the fire resistance of a load-bearing CLT element is usually calculated with the combustion rate given in the relevant standards (such as Eurocode 5). In case of a fire, the CLT elements will maintain their structural integrity within for a calculated duration.

A flame retardant treatment is often required additionally, as it helps to prevent ignition and slow the spread of fire from one element to another or over larger surfaces. Nordtreat’s NT DECO flame retardant improves the reaction to fire performance of the CLT elements and contributes to the fire protection and the safety of the building. As a result, CLT elements treated with NT DECO achieve a reaction to fire class B-s1, d0.

As CLT is widely used in large-size and multi-storey buildings like apartment buildings, commercial premises and public buildings, there is a need for reliable fire protection of the CLT elements. 

4. REACTION TO FIRE PERFORMANCE OF CLT

The reaction to fire performance of NT DECO treated CLT has been classified as B-s1, d0 according to EN 13501-1. The tested CLT structures were 90 mm thick and made of spruce. The visible surfaces were treated with 350 g/m² of NT DECO flame retardant.

Concerning solid wood elements, the product can be classified according to the product standards prEN 16351:2018 (CLT).

CLT is regularly manufactured according to the European standard EN 16351. Many of the manufacturers still hold European Technical Assessments (ETA) as approval for the use of CLT in building and construction from the time before the harmonization of the standard. Either the EN or the ETA is the basis for the CE marking of the CLT.

The Euroclass B-s1, d0 certification is valid only when the CLT has been treated according to the instructions of Nordtreat and when the treatment is duly documented.

6. NT DECO COLOUR OPTIONS

NT DECO is available in clear or semi-translucent colours. This enables the toning of the CLT surfaces to match the surrounding materials. For large CLT surfaces, like walls and ceilings, usually, the best choices are found in our Natural Shades collection.

7. CLT FIRE PROTECTION TREATMENT METHODS

There are two ways to reach the Euroclass B-S1, d0 reaction to fire performance with NT DECO flame retardant:

8. DURABILITY AND MAINTENANCE OF CLT FIRE PROTECTION

Fire protection with NT DECO flame retardant is a reliable, sustainable and cost-efficient solution. The required amount of the semi-translucent flame retardant is protecting the wooden surface not only against the spread of fire but also gives protection against wear and use traces that usually occur in the use cycle of a building.

In indoor conditions, no maintenance service is needed if the treated wood surface is not mechanically damaged. When needed, the maintenance treatment should be done with the same flame retardant product that was originally used.