The egg shaped observatory gets its namesake from a Dutch wordplay joke. Tij is the Dutch word for tide, referencing the changing tides in its location - Haringvliet, but pronounced quickly, it sounds like the dutch word for egg. The designers ran with the joke and produced a beautiful ‘egg’, or sphere shaped wooden structure for viewing the surrounding coastline.
Tij is part of a series of landscape and architectural projects that were erected to celebrate the opening of the Haringvliet dam ducts, which were built in the 1950’s. The opening of the dam sluices was an important step forward in increasing the salt resistance, water levels, and biodiversity of the region. Tij is the largest of the bird and animal observatories that now dot the area.
Tij takes on an appropriately egg shaped form, specifically modelling itself on the egg of the sandwich tern - the iconic bird of the area.
A path leading up to the observatory comes mostly in the form of a tunnel covered with sand, to minimise disturbance to the wildlife. Salvaged mooring posts and planks were used to construct the underground wooden path.
As the bottom of the structure floods a few times a year due to king tides, different timber species were used for different parts of the sphere. The lower half is made from Accoya timber, which is highly rot and water resistant. The upper half, which stays out of water all year, was constructed from more generic pine. The roof was thatched using local reeds - a sustainable, low cost and minimal impact material. The floor is a composite of concrete foundations and a CLT timber floor slab, providing a structural stabiliser and viewing platform. Steel was used for railings and stair stringers.
The observatory not only takes aesthetic cues from the egg, but also its structural makeup. A ‘nest’ that houses the egg has ‘feathers’, made up of structural chestnut posts, surrounded by reeds and dunes, which partially bury the egg.
The spherical ‘egg’ body was generated parametrically via CAD software, allowing the extremely accurate makeup of the individual timber members to be fabricated with a CNC router off-site. 3D modelling of the project allowed experimentation and precision in achieving the best strength-to-weight ratio, form building, and choosing where openings would cut.
Designing the structure parametrically in 3D space also allowed engineers to specify timber sizes required to hold the sphere up, and resulted in a large span timber structure with relatively small timber components.
The whole structure is made from 402 parts, all cut in a factory, and all assembled on site. The parts can be easily disassembled and reassembled at a new site, and in combination with the natural material use, the life cycle of the project is almost completely circular and sustainable.