Building a daringly formed new skyscraper, in a city renowned for its skyline is no easy task.
With significant height, numerous cantilevers and an extremely narrow floorplate,
56 Leonard proved highly challenging to engineer and construct.
This, is the story of New York’s “Jenga Tower”.
Located in Lower Manhattan at the intersection of Church and Leonard streets in Tribeca,
the 60-storey skyscraper’s unique form sets it apart from New York’s many rectangular towers.
Designed by Swiss architecture partners Herzog & de Meuron, it is comprised of a series of
stacked blocks that are increasingly offset from one another as the tower rises
– giving the building its Jenga-esque form.
Built in a height-restricted historic district amongst mainly low rise structures,
56 Leonard occupies a plot that was previously owned by the New York Law School,
and that is exempt from these height regulations.
Such privilege gives the luxury residential apartments in the tower spectacular unrestricted views across the city.
With a width-to-height ratio of 1:10.5, the skyscraper is part of a growing trend for
super skinny residential towers in New York.
It joins the recently completed 432 Park Avenue designed by Rafael Viñoly,
while SHoP’s 111 West 57th and Jean Nouvel’s 53 West 53rd are both under-construction.
The 831-foot, 253 meter tall reinforced concrete tower contains just 145 apartments that range
from 650-square-foot studios to penthouse apartments of more than 6,000 square feet in size.
56 Leonard’s internal space is divided into several zones; the lobby, townhouse residences,
tower residences and ten spectacular penthouses near the summit.
These are supported by numerous amenities including a theatre, swimming pool, fitness suite and conference centre.
Floor-to-ceiling glass walls are sandwiched between concrete floor slabs creating internal spaces
that are a minimum of 11 feet high, and almost 19-foot high in some penthouses.
Being able to call such a unique location your home is not cheap
– 56 Leonard’s most expensive penthouse is being marketed at a cool $65M USD.
Building a super-skinny skyscraper in the heart of New York is not easy, but it was the construction of
56 Leonard’s top ten floors – containing its cantilevered penthouses or “sky villas”
– that presented the project team with their greatest challenge.
Some of the top floor slabs cantilever by up to 25 feet (or 7.5 metres) out of the building.
While for the smaller cantilevers the thickness of the concrete floor slabs provides sufficient support,
for those over 15 feet, additional beams had to be incorporated within each floor plate.
The building’s stacked and shifting volumes meant that no two consecutive floor plates were the same,
a feature that made transferring loads down through the structure incredibly complex.
To overcome this issue, engineer WSP designed “walking columns” that transferred loads
from one location to another as they progressed down the building.
A key consideration when designing a tower so thin is its tendency to sway in the wind
– particularly toward the upper levels – a sensation that would not be pleasant or tolerable to those living in its residences.
To address this, engineers significantly increased the rigidity of the structure,
connecting the columns to the core with outriggers at floors 32 and 46 and with belt walls that wrap the perimeter.
Additionally on the 56th mezzanine floor, a water tank containing 130,000 litres of water
helps dampen the building’s movement in the wind.
Now complete, 56 Leonard stands prominently in Lower Manhattan,
an impressive feat of engineering that makes a notable and unique impact on the world’s most famous skyline.
If you enjoyed this video and would like to get more from the definitive video channel for construction,
subscribe to The B1M.