Restoring the base of the Knight’s Tower at Kasteel de Haar

In around 1890, architect Pierre Cuypers commissioned the current Kasteel de Haar. This included the Knight’s Tower, which was built on the brickwork of the old ruin to a height of approximately 34 metres. As time went by, the tower subsided and a wall of jet-grout piles built in 2002 was not enough to fortify the foundation and stabilise the subsidence.

Client:
Stichting Kasteel de Haar
Location:
Haarzuilens
De Haar 1
De Haar - detail vijzelen

Project

It was decided to build a new foundation for the tower, consisting of a 600 mm thick concrete floor resting on screw-injection piles.

In order to build this new foundation, the tower was structurally supported on two levels with a temporary screw-jack bearing construction inserted through the existing brickwork. The first structural support was inserted into the Cuypers brickwork at a height of approximately 6 metres above ground level and given a foundation of newly sunk piles. This provided the existing foundation with sufficient ‘relief’ so that structural support could be applied to in the bottom part of the tower.

The work location was made accessible by applying sand terps around the tower and building a temporary bridge over the moat. Part of the facade had to be broken open in order to get inside.
 
The then State Secretary Van der Laan launched the project by hacking away the first stone.