Terraces and outdoor spaces: designing structures adapted to climatic constraints

Once considered mere extensions of the building, outdoor spaces now occupy an important place in architectural and landscape projects. Terraces, pontoons, walkways and public squares must, however, withstand constant exposure to ultraviolet radiation, humidity, freeze-thaw cycles, wind, and heavy foot traffic.

In this context, the material's behavior over time becomes a specification criterion. Resistance to biological degradation, dimensional stability, maintenance requirements, and changes in appearance must be assessed according to the structure's use and exposure.

In Oslo, a deck exposed to the marine environment

In Oslo, the Sørenga Harbour Pool, also known as Sørenga Sjøbad, exemplifies the use of wood in a public space located on the edge of the fjord. The project includes platforms, walkways, and swimming areas subject to water, climatic variations, and sustained use.

Kebony wood was chosen to clad the platforms and create continuity between the different uses. The material gradually takes on a silvery-grey hue under the effects of sunlight and weathering. According to the manufacturer, this surface evolution does not alter its durability.

Cladding exposed to the winds of the Fleinvær archipelago

In the Norwegian archipelago of Fleinvær, the Arctic Hideaway comprises several structures designed to house artists in an isolated environment. The buildings are exposed to strong winds and rapidly changing weather conditions.

The project uses Kebony Character cladding. According to the manufacturer, the choice of material was in response to the search for an envelope adapted to the northern climate, requiring little maintenance and capable of evolving visually with the landscape.

The Green Arch in Meise combines conservation and architecture

In Belgium, the Green Ark at the Meise Botanic Garden is a 7.600 m² complex dedicated to plant conservation, research, and public awareness. Inaugurated in May 2024, the complex comprises 22 climate-controlled greenhouses and houses over 10.000 plant taxa, including many endangered species.

The visitor pavilion, designed by NU architectuuratelier and Archipelago Architects, is covered by a hyperbolic paraboloid vault. Its envelope uses Kebony Clear shingles, which complement the complex geometry of the roof and its integration into the botanical garden.

A process for permanently modifying wood

Developed in Norway, Kebony technology is based on a patented wood modification process. This involves impregnating softwood with a bio-based liquid containing furfuryl alcohol, then inducing its polymerization through heat treatment.

The process permanently alters the cell walls of the wood. According to the manufacturer's technical data , a Kebony Clear product intended for decking has a durability class of 1 according to EN 350 and falls under use class 3.2 according to EN 335, when installed in accordance with the installation instructions.

The technical data sheet also indicates that the maximum tangential swelling between the dry and wet states is reduced to 4%, compared to 8% for untreated radiata pine used as a reference. Kebony Clear wood is made from FSC-certified radiata pine.

Durability also depends on the design of the structure.

However, the material's performance alone cannot guarantee the longevity of a terrace or cladding. The design of the structure, water drainage, ventilation, the choice of fasteners, and adherence to installation guidelines remain essential.

The manufacturer's warranty is therefore conditional upon compliance with its installation and maintenance guides. It specifically excludes damage resulting from poor design, incorrect installation, exceeding the specified wind loads, or certain extreme weather events.

For specifiers and companies, climate adaptation of outdoor spaces therefore requires comparing the declared performance of the material with the actual constraints of the site, the intensity of use and future maintenance conditions.