Building D(emountable) in Delft is a four-storey office building that has a hybrid structure combining a steel frame with wooden elements. The building project was fast: it took just a few months from the drawing board to a finalized building, and the load-bearing structure was put together in only three weeks. Fast, light and green Kerto® LVL (laminated veneer lumber) elements were easy to install in the middle of a busy city.

Building D(emountable) in Delft’s city centre is a four-storey high office building designed by the architectural agency cepezed. They planned the building to be rented out to different-sized creative companies.

“I was impressed by the speed in assembly,” says cepezed founder and architect Jan Pesman.

“The whole stability structure was put together in only three weeks. We are planning to do this type of building more often, and we are very pleased with the results, too. Kerto LVL elements were practical and really suitable for prefabricated, industrial construction methods.”

Combining steel and wooden elements uses the best of both worlds

The Building D(emountable) is an elegant combination of steel, wood and glass. It has a steel framework with L-shaped load-bearing beams. The glass of the curtain wall façade is mounted directly to the steel columns, without intermediate window frames. Kerto LVL elements are used for the floors.

“In the Netherlands, these elements are not commonly used,” explains structural engineer Elise van Westenbrugge-Bilardie from IMd consultative engineers. “And certainly not combined with steel in a hybrid construction. But cepezed was convinced of the potential,” she continues.

“The Kerto elements combine very well with the steel of the structure,” explains the project manager Jan Houtekamer from cepezed’s own construction coordination company cepezedbouwteam. “And they are way lighter than concrete floor slabs, so they make for really efficient use of materials.”

Light-weight wooden elements are easy to handle

“One of the goals was to make the building as light as possible,” says van Westenbrugge-Bilardie. “cepezed gave us the idea to use wooden elements with the design. We also wanted to use the smallest elements possible, so the parts are easy to transport to site and combine them there.”

This was a great prototype for sustainable building.

Jan Houtekamer, project manager, cepezedbouwteam

The roof and floors consist of wooden rib elements based on Metsä Wood’s Kerto-Ripa® design system. The elements are constructed of Kerto LVL S-beams measuring 45 mm in width and 360 mm in height, as well as 25 mm Kerto LVL Q-panels. Each element is 1,800 mm in width, with an exception for the first and last one on each floor, which are both 2,400 mm wide. Most elements span the entire depth of the building, some 10.6 metres.

Wood supplier De Groot Vroomshoop brought the elements to the site in batches. In about three days, the elements were all at the site and positioned to be ready for the erection of the building. Houtekamer is sincerely happy with the finished project:

“This was a great prototype for sustainable building. What I liked about the Kerto LVL elements is that they have all the qualities of industrial components,” he says. “The dimensions are slender and stable compared to most other products made of wood.”

Easily mountable – and demountable

The Kerto LVL elements were prefabricated in de Groot Vroomshoop’s factory by connecting Kerto LVL Q-panels and Kerto LVL S-beams together by gluing, pressing and nailing. On site, the elements were placed on the L-shaped beams with a small gap in between them.

“The gaps allow for the throughput of a row of internal columns and are also used for the integration of the lighting elements into the floor system,” explains Houtekamer.

All the different construction components were put together with the minimum of connections. The connections were designed to remain reversible, meaning that the building can be easily dismantled. Using small wooden elements that are quick to assemble also means that the whole process can be reversed, if needed:

“You can also dismantle the building and rebuild it somewhere else. If needed or wanted, you can just move this building wherever you want,” says van Westenbrugge-Bilardie.

More hybrid buildings to come

Using prefabricated elements was a good prototype project for cepezed for future hybrid building projects.

“With this process of on-site assembling and prefabricated elements, we can use wood more frequently in the future. It's a smart and sustainable material,” says Houtekamer. “I think it's very easy to combine wood in this manner with a steel structure.”

We are definitely looking forward using Kerto LVL elements again.

Jan Pesman, cepezed founder and architect.