In the dense, historic fabric of London’s skyline, architecture usually competes for height or iconic silhouettes. However, at Embassy Gardens in Nine Elms, the narrative took a horizontal—and decidedly transparent—turn. Suspended ten storeys in the air, the Sky Pool has become a global symbol of engineering audacity, bridging the gap between two luxury residential buildings with nothing but 14 metres of crystal-clear acrylic and 375 tonnes of water.
The story of the Sky Pool is not just one of luxury leisure; it is a groundbreaking case study in material science and structural movement. To understand how a swimming pool can “float” between buildings in one of the world’s most regulated cities, one must look beneath the surface of its shimmering blue water.
1. The Concept: A Bridge of Light
The narrative of the Sky Pool began with a spatial dilemma. The developers of Embassy Gardens wanted to link the rooftops of two residential blocks—Legacy Buildings 1 and 2—to provide residents with a seamless experience between the two amenity decks. A traditional bridge felt heavy and obstructive. The solution was to create something that felt “invisible.”
The resulting design is a 25-metre long swimming pool, with 14 metres of its length suspended entirely in the air. Unlike traditional pools that are dug into the earth or set into a concrete roof, the Sky Pool is a self-supporting structure that acts as a structural bridge.
2. The Material Narrative: Why Acrylic, Not Glass?
When people first see the Sky Pool, they often assume it is made of glass. However, glass is a brittle material that does not handle the “twist and pull” of two independent buildings well. The hero of this story is High-Grade Acrylic.
The pool was fabricated in Colorado, USA, by Reynolds Polymer, using panels of transparent acrylic that are 200mm (8 inches) thick on the floor and 180mm thick on the side walls.
The Clarity Factor: Acrylic has a refractive index very similar to water, meaning the “walls” of the pool almost disappear when the pool is filled.
The Strength Factor: Unlike glass, acrylic is flexible. It can expand and contract with temperature changes and absorb the vibrations of the city without cracking.
3. Engineering the “Move”: Handling Building Sway
The most complex chapter of the Sky Pool design is the narrative of Differential Movement. No two buildings move in exactly the same way. Wind loads, thermal expansion, and even the varying weight of residents can cause the two apartment blocks to sway independently.
If the pool were bolted rigidly to both buildings, the sheer force of the buildings pulling in opposite directions would tear the structure apart.
The Solution: The Sliding Bearing
The Sky Pool is not actually “fixed” to both buildings. Instead, it is anchored to one building while it “sits” on the other using a sophisticated bridge bearing system.
Fixed End: On one building, the pool is securely fastened to the concrete structure.
Sliding End: On the opposite building, the pool rests on steel “shoes” equipped with Teflon-coated bearings.
This allows the buildings to sway, vibrate, and shift by several centimetres without transferring that stress to the acrylic tub. The pool essentially “floats” on its supports, much like a highway bridge spans a river.
4. The Weight of the World: 375 Tonnes of Water
Water is incredibly heavy, weighing 1,000kg per cubic metre. The Sky Pool holds approximately 375 tonnes of water. Supporting this mass over a 14-metre span without visible steel beams underneath required a “monocoque” design approach.
The acrylic tub itself is the primary structural member. The side walls act as massive deep beams that support the weight of the floor and the water. To ensure safety, the pool is equipped with a secondary steel frame that provides “fail-safe” support, hidden within the stainless steel trim that outlines the pool’s top edge.
5. Technical Comparison: Sky Pool vs. Traditional Rooftop Pool
| Feature | Traditional Rooftop Pool | London Sky Pool |
| Material | Reinforced Concrete / Tile | 200mm High-Grade Acrylic |
| Support | Direct Building Load | Suspended Bridge Geometry |
| Movement | Static with Building | Dynamic (Sliding Bearings) |
| Transparency | None | Full 5-Sided Visibility |
| Maintenance | Standard Filtration | Acoustic & Vibration Monitoring |
6. The Safety Narrative: Lightning and Filtration
Being suspended 35 metres in the air in a city known for its unpredictable weather brings unique safety challenges.
Lightning Protection: Because acrylic is an insulator, the pool is surrounded by a copper earthing system embedded in the stainless steel frame to safely channel lightning strikes into the building’s ground.
Cleaning and Clarity: To maintain the “invisible” look, the pool utilizes a high-pressure filtration system that cycles the water constantly. Specialized underwater vacuum robots are used to clean the acrylic floor, as even a small amount of sediment would be visible from the street below.
7. The Experience: The “Flying” Swimmer
From the swimmer’s perspective, the narrative is one of sensory deprivation and exhilaration. Looking down through 20cm of clear acrylic, you see the pedestrians on the Nine Elms sidewalk 115 feet below. To the north, the swimmers have a panoramic view of the U.S. Embassy and the Houses of Parliament.
It is an architectural experience that challenges the brain’s perception of “solid ground.” The water provides the buoyancy, but the acrylic provides the courage to swim into empty space.
Conclusion: A New Horizon for Urban Design
The Sky Pool in London is more than a luxury amenity; it is a testament to how far we can push the boundaries of materials and engineering. By treating a swimming pool as a bridge, the designers at HAL Architects and structural engineers at Eckersley O’Callaghan have created a new narrative for urban density.
It serves as a reminder that the spaces between buildings are just as valuable as the buildings themselves. In the future of “Vertical London,” we may see more structures that utilize transparency and movement to link our sky-high communities.
