The O’Portune slab is a horizontal timber panel, assembled without glue using nails or screws, and designed for large-span floor applications.
History.
With the rise of timber construction, wooden floors and ceilings emerged, helping to promote more environmentally friendly buildings. The O’Portune slab was designed in 1999 by Jean-Luc Sandoz, head of research and development in wood materials at the EPFL, for the Swiss National Exhibition 2002. In 2000, more than 50,000 m² of offshore wooden flooring was installed on metal pipes (a dismantled gas pipeline) laid on Lake Biel and Lake Neuchâtel.
The O’Portune slab was patented in 1999. The patent expired in 2019, after which the system became a commonly used structural element in mass timber construction, particularly for its environmental and recyclable benefits, as well as for its acoustic performance that contributes to interior comfort.
Development.
Tropical wood.
Originally developed for fir and spruce, the process has been adapted for use with other wood types, such as poplar and tropical wood. The latter is used by the French space agency CNES for its new buildings at the Guiana Space Centre.
Local wood.
Research is ongoing into using different wood types, particularly poplar.
Hybrid timber–concrete construction.
When topped with a concrete layer, the O’Portune slab becomes a timber–concrete composite system called the D-Dalle, which increases both structural and acoustic performance to meet the requirements of a building. It was developed by the Swiss company CBS-CBT. This system offers spans of 8 to 18 meters without intermediate supports and maintains a low weight (250–400 kg/m²).
Technical description.
O’Portune slabs are manufactured on-site or in workshops and form a horizontal plate-based structure with high mechanical performance and/or long spans – up to 12 m without supports.
The slab is made of staggered wooden boards, screwed or nailed together to improve both structural and acoustic performance without increasing weight.
The floor modules are prefabricated in workshops using staggered boards with a cross-section of 180 × 50 mm, which increases the structural height. With boards 180 mm high and an 80 mm overlap between the lower and upper boards, the effective structural height used in calculations becomes 280 mm.
Boards are assembled with 6 mm diameter, 180 mm long screws. To distribute stress evenly, the slabs are covered either with OSB boards (11 mm thick) in standard areas, or with Kerto laminated veneer panels (27 mm thick) in terraces and storage zones. The plywood is screwed onto the top of the boards with a screw every 300 mm. As a whole, the structure behaves as a membrane under horizontal stress.
The architectural firm Wilmotte & Associés listed the O’Portune slab as number 13 in its reference collection of construction elements.