The first of its kind and a truly remarkable feat of engineering, a transparent swimming pool spans between two apartment buildings ten storeys in the air.

Sky Pool is the world’s first fully transparent swimming pool, spanning like a bridge 15m between two adjacent residential buildings 10 floors up on Ecoworld Ballymore’s Embassy Gardens development in south London. Sky Pool forms the centrepiece of the new Estate, allowing swimmers a dizzyingly clear view of the park 35m below.

The pool is constructed in clear acrylic. The side walls of the pool are 180mm thick and 3.2 metres deep. Its base is 360mm thick and the whole pool weighs 50 tonnes and contains a total of 150tonnes of water, 100tonnes of which is carried by the acrylic ‘bridge’. Because of its size, Sky Pool has been constructed in separate sections with transparent bonded joints cleverly designed to maximise the bond area and avoid areas of high stress.

Some significant engineering challenges have been addressed in developing the structural solution for this spectacular new pool. The pool structure has a clear span of 15m between the buildings. The side walls form deep beams capable of spanning this distance whilst carrying the weight of the water, as well as resisting the hydrostatic water pressure on the sides and the wind loads.

The two buildings are subject to normal movements, which are inherent to buildings of this scale including wind sway and foundation settlement. The pool structure deals with these movements by avoiding rigid connection at both ends; it slides on bridge bearings whilst maintaining watertightness.

An additional 5m length of pool sits over the buildings at each end to make a total length of 25m. These parts are constructed in stainless steel. They are tied together across the acrylic by two high strength, spring-tensioned, stainless streel rods 38mm in diameter which sit beneath the pool.

A bonded acrylic structure offers less intrusive joints and connections and greater transparency. The refractive index of acrylic, close to the value for water, will also result in much less distortion when viewing through the water or from outside.

A project case study by Eckersley O’Callaghan Technical Director Graham Coult for Springer Nature can be read here. 

London, UK

EcoWorld Ballymore

HAL Architects

Simon Kennedy