"It is an answer to a very clear demand from the market," says Lars Bastiaansen. And that is of course good news for the Sales Manager at Boogaerdt Hout in Krimpen aan de Lek. 'Architects and developers increasingly want wooden cladding. Or, for example, wooden finishes on the underside of balconies and overhangs. These often have to meet fire class B, the Building Decree is very clear about this. Until now you have not been able to avoid a closed system using wood that has been impregnated or treated with a fire-retardant coating.'

While open facade cladding: the slats, preferably in different widths, attached to the facade at some distance from each other, is often considered aesthetically more attractive. Bastiaansen: 'In addition, when treating facade wood with products that achieve fire retardancy, it usually does not provide a conclusive answer. You may also be faced with a maintenance program, products that can have a negative environmental impact, etc.

Boogaerdt Hout, specialized in the import and sale of tropical hardwood species for various applications, also sells these other facade products. But it is being handled more and more precisely. Bastiaansen: 'In the past you simply sold the wood on cutlery. Due to the arrival of the WKB, you will increasingly inform the architect or contractor how the facade cladding should be applied. Our products are part of the total quality performance of a facade.

Forestlines® Façade cladding

And that's where the solution comes in: Forestlines®, invented and developed by Steven Paulussen, owner of Houthandel Paulussen in Retie, Belgium. He won all kinds of design and product awards with it last year. It has recently become available for sale at Boogaerdt Hout (and two other specialized Dutch timber traders).

The idea and application is based on a material property of aluminum: that it conducts heat. The wooden planed facade parts of 20 mm thick are slid and connected into aluminum strips with a special profile. The planks lie in a blind connection over the screws that attach the strips to the rails.

Bastiaansen: 'So far the system has passed the test especially well in the vertical direction.

The aluminum creates a flammable strip between the wooden parts. And so there is a reduction in the flammable surface area. An additional effect is that the aluminum extracts the heat from the wood and distributes it over this larger surface. The facade can absorb more heat before it catches fire.

What is special is that the complete system: substrate fire class A, rules and then the Forestlines® cladding, has been tested for fire behavior (in the Peutz fire lab) and certified. In connection with the WKB, it is no longer sufficient to supply a wood product with a certain fire behavior (product performance), the entire system as it is applied, 'end-use', must comply.

Bastiaansen: 'Many types of wood have already been tested. Untreated, that is, because that is precisely the unique thing about this system. What I find remarkable is that we noticed that wood with a high density does not appear to burn any less well than lighter wood. That goes against existing trading knowledge. This says that the heavier a type of wood is, the less it burns. So there is every reason to always test it thoroughly.'

Wooden cladding fire class b

Those that have passed the test so far include the (also not light) Basralocus, Jatoba, Tali, Tigerwood and Okan. And then only planed and in widths between 65 and 135 millimeters. The aluminum profile has a black finish as standard, but is in principle available in every conceivable color, so architects can go wild. Aluminum is of course not a biobased product, but the metal is easily recyclable. Forestlines® profiles are guaranteed to contain at least 70 percent recycled aluminum.

Bastiaansen: 'We already have this product on the drawing board for various projects. If a designer chooses an open wooden facade that must achieve fire class B, especially if it must also be made of untreated wood, then this is now one of the few good, end-use tested options.'

Article: Houtwereld No. 7 Facade cladding June 2023

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