Project Focus: Post-tensioned Concrete at Further Lane

East Hampton, New York
For a private residence in the Hamptons, the design of this signature lap pool is both a feat of imagination and engineering.

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The pool, designed by Selldorf Architects, clear spans 75 feet across the ocean-view veranda, with a transparent acrylic bottom. Carrying 24,000 gallons of water, the structure of the span needed to resist an additional 200,000 lbs of dead load. With an infinity edge as a design imperative, the only option to achieve the span without deflection was post-tensioned concrete.


The structure of the pool is comprised of two main post-tensioned girders on either side of the pool connected together with a series of post-tensioned link beams at the bottom of the pool which frame the acrylic panels. Each girder contained 26 bonded 1/2″ diameter draped tendons with each tendon requiring a tension of 33.5 kips. This was achieved with hydraulic jacks pulling at 7000 lbs of force and elongating the cables up to 6 5/8 inches over their 75 foot length. The process of post-tensioning created a slight camber in the beams which was offset by the weight of the added water to a level condition ideal for the infinity exterior edge.


These construction images explain the sequence of post-tensioning the pool structure including the layout of the strands as well as the equipment used during the tensioning process. After curing, the pool was load tested to capacity with water to verify the exterior edge condition prior to the installation of the infinity edge.  

Double Pane

(Image Credit: Men At Work Construction)
Client: Selldorf Architects
Year: 2015