February 2021 - Without a tower, the historical town hall in Bolsward looks quite bare. The deathwatch beetle had damaged the octagonal wooden tower so badly that it was unsafe to leave it in place.
To prevent accidents, the tower was therefore dismantled in three parts, stored and carefully inspected in September last year.
The deathwatch beetle has a preference for oak and it is mainly found in historical buildings, where the wood is full of fungi and moisture. The inspection showed that the beetle had attacked not only the tower but also wooden beams in the rest of the town hall. A thorough renovation will be needed to save this listed building.
Steel instead of wood
The municipality chose to install a steel girdle in the tower because steel is more enduring and stronger than wood. The steel structure will provide the support that used to be given by the damaged wooden beams.
Because it emerged later that there wasn't enough space in the upper part of the tower for a steel girdle, the existing wooden structure is being repaired and reinforced here. The steel replacement continues to be needed because most of the damage was located in the lower part of the structure. The steel provides stability and it will be attached to the wooden structure.
The steel structure consists of a central element measuring 2.85 x 2 metres and weighing
3 tonnes that was brought in through the top of the tower. Because the tower consists of wooden jambs with connecting beams, there was not a lot of room and the installation of the new foundation really was a precision job.
Once it was positioned at the bottom of the tower, the structure was tilted and the steel “legs” were mounted on it. This structure now serves as the foundation for the tower and it will ensure that it is structurally secure and can stay in place for the next hundred years without the city authority having to worry about the tower.
The steel spider structure and the heavy profiles of the legs of the spider were produced by Visser Konstruktie. Rotocoat hot-dip galvanised the spider and the legs so that the structure now has enduring protection from rust. The steel structure was then painted in RAL 9005.
The tower is scheduled to be put back into place early next year. The listed building has been restored and preserved for the future because a town hall without a tower just isn't the real thing!
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