Woodia CLT balconies

11 5 2020 | Environmental safety | Fire regulations | wood construction

Certified CLT fire protection promotes carbon neutral construction

With massive CLT elements, it is possible to minimise environmental impacts and carbon footprint of construction without compromising safety. Woodia is the first Finnish manufacturer who has certified the CLT fire protection treatment in accordance with European class B-s1, d0 (EN 13501-1) requirements. The company also provides CLT fire protection as a service to other CLT element manufacturers and construction companies.


Photographs: Woodia

CLT made of cross-glued wood is an excellent construction material, because it is light, bearing, robust, easily modified, environmentally friendly and, as an organic material, it also makes buildings more attractive. It’s no wonder that CLT is becoming ever more popular in both public and residential buildings.

The CLT elements minimise the carbon footprint and environmental impacts of buildings, and they are suitable for both wood construction and hybrid construction combining the use of wood and other construction materials. In construction sites with over two storeys, all visible surface materials, such as CLT, often need to meet the requirements of Euroclass B-s1, d0.


Elements built from CLT are safe, and their behaviour in fires is well known. In fires, massive CLT elements last long without collapsing, because the carbon layer forming on the surface protects the inner layers of the element from burning.

Since untreated wood in itself is rated as a D class surface material, it is often necessary to protect its surface to gain a higher fire class (classes C and B). Previously, this was a problem, because the compliance of CLT with the fire protection requirements has been quite difficult and complex to proof in on-site environments.

As for on-site CLT fire protection treatments, the situation has not changed. Building control authorities approve the surface treatment site-specifically without full certainty whether the fire protection actually meets the requirements of the fire class required for the surface treatment. Woodia decided that eliminating this issue would benefit everyone involved in construction, so they invested in controlled fire protection.


Woodia puuparvekkeet Kalliorinne-730

Wooden balconies by Woodia in Kalliorinne



Nowadays, it is easy to verify whether the fire protection of CLT elements is compliant or not. Nordtreat has certified the fire protection treatment of CLT with NT DECO in accordance with European class B-s1, d0 (EN 13501-1). This expertise was utilised when Woodia was the first Finnish manufacturer who certified the industrial fire protection treatment of CLT with all fire retardants accepted for the process.


“CLT fire protection that is certified in accordance with fire class B-s1, d0 ensures fire safety and improves the efficiency of construction. We certified the industrial fire protection of CLT elements in September 2020 in close collaboration with Nordtreat and other manufacturers of certified fire retardants.”

Jouko Rintala, Managing Director, Puuidea Oy (Woodia)


Certified fire protection is performed in monitored conditions. The treatment itself and its conditions are strictly controlled and documented. Compliant fire protection treatment is performed in accordance with the instructions given by the manufacturer of the fire retardant in certain humidity and temperature conditions. In addition, to achieve even absorption of the fire retardant and the desired shade, a controlled amount of the fire retardant has to be applied in several runs at certain intervals.

Controlling the treatment conditions on-site is very demanding in practice, and this is why both Woodia and Nordtreat recommend that architects and construction companies would choose CLT with industrial fire protection in their construction sites. In doing this, both the developer and building control authorities can be certain of the quality and compliance of the treatment.

The certification for fire protection treatment is specific to the production site, which means that Woodia performs the fire protection treatment for its own and other manufacturers’ CLT elements at its production site in Teuva.


Woodia is the leading manufacturer of wooden balconies in Finland. In addition, the company produces stair elements and lift shaft modules made of CLT and glulam with certified fire protection. These products are a perfect fit for carbon neutral construction, because their environmental impacts have been assessed and their carbon footprint calculated.

Woodia’s CLT balconies with certified fire protection are ready balcony elements which can be installed as suspended balconies to the exterior wall or as balcony towers founded on the ground. All wood surfaces and support structure spaces of the balcony elements have been treated with certified fire protection, because the timber cladding used are supplied by partners who have certified their industrial fire protection process.


“We have been the pioneers in the product development of installation-ready CLT balconies. Our certified fire protection treatment that meets the requirements of the required fire class offers significant added value to our customers and brand new growth opportunities for us.”

Jouko Rintala, Managing Director, Puuidea Oy (Woodia)


The CLT balcony is notably light – it weighs only a fifth of the weight of a similar concrete balcony. This allows designers greater leeway in their designs, as balconies improve the attractiveness of buildings. Wooden balconies might be larger in size, and they can be placed also asymmetrically onto building walls.

Woodia CLT-parveke-730

Suspended retrofit balconies by Woodia

Using versatile CLT in construction is an easy and efficient way to increase the share of wood that functions as a carbon sink within various construction sites. The building frame can typically be either wood or concrete.


The increasing demand for environmentally friendly CLT increases also the demand for certified fire protection that meets the requirements of the fire class B-s1, d0. Thanks to Woodia, this is now possible also for other manufacturers of solid wood elements. Everyone can now take care of the appropriate fire protection for their products without investing in an own treatment facility suitable for massive elements and in certified expertise.

For construction companies, the certified and documented fire protection of CLT minimises manual labour on-site and offers a reliable proof of the fire protection quality.


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