netherlands-based studio RAU architects, in collaboration with RO&AD architecten, design the egg-shaped structure entitled ‘T IJ as part of a series of objects designed to celebrate the opening of the ‘haringvliet sluices.’ a group of dam-like hydro constructions, the ‘sluices’ were opened in order to improve water quality and biodiversity while stimulating fish migration. the structures work to create a new, salt-resistant and salt-loving natural environment. the biodiversity in the surrounding nature reserves will increase while a more robust, healthier ecosystem will develop in the upcoming years. to let people experience and explore these changes, a series of bird observatories, including ‘T IJ, have been designed on the haringvliet site.

road architecten tij
all images by katja effting



‘TIJ’ meaning ‘tide’ is a dutch word-play which refers to the returning tides in the haringvliet, and when pronounced quickly means ‘the egg.’ the egg-shaped bird hide designed by RAU and RO&AD is situated in a nature reserve near the netherlands’ haringvliet sluice. as these islands are breeding grounds and home to several species of birds, the observatory is part of a large scale landscaping plan which offers a place to view several different species.

road architecten tij



to prevent the birds from being disturbed, the last section of the path takes the form of a tunnel built of up-cycled mooring posts and second-hand azobe planks which were once used in the brick industry. the tunnel is covered in sand to provide a habitat for native birds such as terns or waders. the outside of the tunnel provides artificial nesting holes for sand martins. the end of the walking route is the egg-shaped bird hide from which an observer can view the species that live in and around the water.

road architecten tij



sitting on a nest of sand, the form of T IJ takes influence from the egg of the ‘tern.’ the structure’s foundation, or the nest of the egg, consists of vertical ‘feathers’ of chestnut poles, reeds, and small sand dunes. the egg itself is parametrically designed to achieve an efficient ratio between form, structural integrity, size of the timber, and size of the openings. the structure has been constructed to provide relatively large spans with small timber parts.

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project info:


project title: ‘T IJ ‘the egg’

architecture: RAU architecten, RO&AD architecten

location: scheelhoek, the netherlands

program: bird obsevatory

construction period: october 2018 — march 2019

design team: thomas rau, ad kil, ro koster, michel tombal, jochem alferink, martin van overveld, athina andreadou, loyse rebord, rodrigo altamirano

client: vogelbescherming & natuurmonumenten

primary structural engineer: breedID, den haag

wood engineering: aalto university, geometria

landscape: H+N+S landschaps architectuur

contractor: van hese infra, middelbur

thatched roof: elg rietdekkers

photography: katja effting