Cantilevered Foundation Sets NYC Tower Apart

New York City construction is no stranger to subway-infringed projects, but nonprofit homeless advocacy group Common Ground’s 98,000-sq-ft, 11-story Schermerhorn House in Brooklyn sets a new standard for foundation solutions. With 40% of the affordable housing footprint overhanging the A, C, E, and G lines, it employs a complex cantilevered design to relieve all loading on the tunnels underfoot.

This unusual foundation comes at no small price. The foundation alone accounts for 25% of the project’s $40-million price tag. Still, says Scott Hughes, project structural engineer from Robert Silman Associates, New York, the cantilever was “the most cost-efficient and expeditious” solution. Although the subway was intended to sustain marginal weight, he says, the Metropolitan Transportation Authority agreed with his firm that the fully load-bearing cantilever bypassed future exigencies of tunnel retrofitting and stringent city seismic codes.

Project superintendent, Eric Rizzo of Marson Contracting, Co., Inc., Bronx, marvels at the foundation’s design, “Everyone that comes here has never seen anything like it.” He motions to the hyperbolic scale of the four rear independent pile caps and the continuous grade beam nearer the subway tunnels.

The frontal continuous grade beam, a massive rebar cage with inch-thick steel bars, assumes all compression from the building and its overhang. Anchored on 60 separate 85-ft-deep caissons – each with a 200-ton capacity – the steel and concrete behemoth measures 10 ft wide, 7.5 ft deep and runs 147 ft long along the path of the subway.

While this continuous grade beam stabilizes the cantilevered north end of Schermerhorn, the four rear, independent pile caps ground the mid-rise tower, counteracting the cantilever’s downward forces. Each 13x13 ft, 7.5-ft-deep concrete cap contains nine 65-ft-deep fitted caissons, each with two threaded steel rods that connect the concrete to a steel plate and seven more steel rods that then attach the plate to an upper steel truss system, currently under construction. “The longer [the caisson], the more stress it can take. It is the friction of the pile that keeps it into place,” says Rainone.

Though the caps and beam prevent vertical loading on the subway lines, annular sleeves about the caissons also preempt any lateral loading. The sand-filled sleeves insulate pile settlement, strategically preserving the dirt around the sensitive subway tunnels. 

Schermerhorn is viewed by many as a pioneer for affordable housing. Project architect Susan Rodriguez of Polshek Partnership Architects, New York, calls the project a “paradigm for the entire city on new, dignified low-income housing.” The facility, partnered by Common Ground and the Actors’ Fund of America, will provide on-site social services, community space, and sustainable benefits like a green roof and natural lighting for its tenants.

Queens Piano Factory Goes Condo

A six-story, former piano warehouse in Astoria, Queens is getting the condominium treatment.

The Piano Factory, a 101,000 sq ft warehouse on Vernon Boulevard was built or the now-defunct Sohmer & Co. Piano Factory. Most recently used as the Adirondack Chair Building, the warehouse will feature 69 condominium units with unobstructed views of Manhattan, as well as more than 9,000 sq ft of retail space.

The conversion of building, which recently received landmark status by the city, is expected to cost the building’s new owner, TTW Realty of Astoria, about $34,000,000. The entire demolition of the warehouse was completed this spring, but the building’s German Romanesque Revival architecture and mansard-roofed clock tower will remain.

The L-shaped building was built along East River in 1886 and was part of the booming 19th century piano manufacturing industry in New York City, which included several other factories around the city. Designed by the architectural firm Berger & Baylies, which is responsible for many warehouses and store and loft buildings in Manhattan, the building became known over the years for its red brick façade and intricate window patterns.

Sohmer made pianos at the site until 1982, when it was sold to Pratt, Reade & Co., a piano keyboard manufacturer who shuttered the Queens operation and moved it to Connecticut.

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