Renovation Krúsrak bridge: Controlled drying process in purpose-built shed

The renovation of the Krúsrak bridge, over the N7 near Sneek, is far from an everyday project. Not only has the entire wooden bridge been moved to a separate work site, a complete shed has also been built around it. This must ensure that the wooden bridge can dry properly. Exactly a project that suits Construction Combination HWO, consisting of Hupkes Wijma and Koninklijke Oosterhof Holman. 

For those driving along the N7 near Sneek, you cannot miss the impressive shed near Krúsrak and Akkerwinde. In this temporary shed a special renovation project is taking place, namely that of the wooden Krúsrak bridge. The client is the Department of Public Works. Construction combination HWO is responsible for the entire renovation. "As a construction combination, we often work together on projects. Our companies complement each other well in terms of knowledge and specialties," says Martien Tolboom, project manager at Koninklijke Oosterhof Holman of Harlingen. Together with Marcus Schiere, product and sales manager at Hupkes Wijma, Martien is closely involved in the renovation. The Krúsrak bridge, built in 2008, shows cracking in the Accoya wood. For sustainable repair, the wood must first be completely dry. The solution chosen: an insulated, demountable shed 21 meters high, 40 meters long and 20 meters wide. "With this we create an energy-efficient and conditioned environment for the controlled drying of the bridge," Tolboom explains. "In the shed, we don't suffer from weather conditions and it minimizes dust and noise emissions to the surrounding area. Inside the shed, the bridge is equipped with scaffolding all around, allowing easy access to all sides of the structure."

Renovation Plan

Construction consortium HWO drew up a renovation plan. Schiere says of the plan, "With fans, heaters and industrial dehumidifiers, the temperature is raised to 35 to 40 degrees Celsius and the relative humidity is controlled. Sensors in the wood monitor moisture levels in real time. A total of about 20,000 liters of water is expected to be extracted from the bridge. Particularly in the south side of the bridge are several 'hot spots' where the moisture content was initially far too high."

Technical repair process

Once the wood meets the Department of Public Works requirements, the repair operation begins. Larger cracks will be repaired with glued-in strips of wood, which absorbs stresses better than filler. In addition, steel studs are replaced with stainless steel ones. All work is carried out according to detailed work and inspection plans, coordinated with knowledge partners Stichting Houtresearch and Lüning.

Sustainable conservation

The final phase consists of preserving the bridge: a multilayer paint system based on epoxy primer and UV-resistant finishing coats will provide long-term protection. All joint seams are also renewed with durable, vapor-permeable sealant. Thus, the structure is optimally protected against moisture, temperature fluctuations and loads.

Proud

By early 2026, Tolboom and Schiere expect to have the job done. A moment they are certainly looking forward to. "Every project has challenges and you learn from every project. We are doing the renovation of the Krúsrak bridge together with a lot of companies, you need each other. We are proud when the bridge is finished and delivered again."