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The Pool

A swimming pool on the roof of a house, in a hurricane zone.

Most of what is unusual about this house you have to be told. The pool you only have to be shown. It is a stainless steel vessel sitting on the roof of a house on an infill lot — which means the structure underneath it was designed, from the footings up, to carry a body of water that weighs more full than the room below it.

Why it is hard

Water is the worst load.

A pool at grade sits in the ground and the ground takes it. A pool on a roof has to be carried by the building, and it does not sit still.

Water is dead load that moves. It sloshes, it is enormously heavy for its volume, and it is directly above finished rooms — so the deck beneath it is doing three jobs at once: carrying the weight, staying rigid enough that nothing below it cracks, and staying watertight for the life of the building. That is why the vessel is stainless and made in a shop rather than built in place, why it arrived on a crane in a single pick instead of being poured up there, and why the waterproofing under it was self-performed rather than subcontracted. Every one of those decisions was made at the footings, years before anybody swam in it.

Engineer of record: Watershape Consulting
Vessel: Diamond Spas — prefabricated stainless steel
Method: Off-site fabrication, single crane pick to the roof structure
Structure below: Precast concrete roof slabs on heavy structural steel, over filled-cell CMU and cast-in-place columns — designed for the loaded vessel
Waterproofing: Structural deck waterproofed beneath the vessel — self-performed
Zone: High-Velocity Hurricane Zone

Team of record is documented. Method and structural notes are attested by the builder. The lift itself is on film below.

The pick

Flown over the block in one lift.

The shell formed first, then the framing under it, then the vessel. Seventy seconds of the piece of work this page is about.

The pick, filmed

Seven seconds, and it is on the roof.

Shot from the floor below, looking up through the opening the vessel was about to fill. The crate is the vessel as it arrived — one piece, lidded, still carrying the fabricator’s mark.

On the roof

Where it landed.

The vessel before the crane pick, resolved on one engineering sheet: plan, elevations, sections and isometric. The… — 01The vessel before the crane pick, resolved on one engineering sheet: plan, elevations, sections and isometric. The archive sheet records 244 square feet of pool surface, 2,567 gallons and a total loaded vessel weight of 29,328 pounds. Shown here as an image for reading, not as a downloadable permit set.

The roof from directly above. An elliptical basin cut into the deck, and the vessel set down inside it. — 02The roof from directly above. An elliptical basin cut into the deck, and the vessel set down inside it.

Closer. The vessel arrived crated and finished — one piece, lidded for the lift, still carrying the fabricator's mark. — 03Closer. The vessel arrived crated and finished — one piece, lidded for the lift, still carrying the fabricator's mark.

The pool in the architect's diagram, arriving as a blue disc cut into the roof — the first colour on any of her sheets. — 04The pool in the architect's diagram, arriving as a blue disc cut into the roof — the first colour on any of her sheets.

And built. The vessel set into the deck with the curved soffit closing over it. Photograph by SOOP. — 05And built. The vessel set into the deck with the curved soffit closing over it. Photograph by SOOP.

Wider, with the terrace beside it — laid in where the fifth diagram put it. Photograph by SOOP. — 06Wider, with the terrace beside it — laid in where the fifth diagram put it. Photograph by SOOP.

The pool was in the massing from the start — drawn as a long cut of water between the two volumes, four years before it… — 07The pool was in the massing from the start — drawn as a long cut of water between the two volumes, four years before it held any.