Designs Unveiled for Atlantic Yards Prefabricated Towers

ForestCity Ratner unveiled the design for what will become the world’s tallest prefabricated steel structure. The 32-story apartment tower at the corner of Flatbush Avenue and Dean Street is part of the $4.9 billion Atlantic Yards project in Brooklyn. Ratner's second tower will be even taller, at 50 stories. Fourteen other residential buildings will follow at Atlantic Yards - all using the same approach.

The 350-unit building would use varying rectangular shapes, colors and glass to break up the mass of the structure, which would sit snugly up against the Barclays Center, the arena for the Nets that is to open in September. Mr. Ratner, chief executive of Forest City Ratner, said that prefabrication, or modular construction, could save construction time and cut costs by as much as 25 percent. Fourteen other residential buildings will be built at Atlantic Yards using the same approach.

Forest City Ratner is also negotiating a labor agreement with construction unions, which have supported Atlantic Yards but could end up with fewer jobs and lower wages for some trades if modular construction is used. Construction is expected to begin early in 2012. Presently, the world’s tallest modular building is a 25-story dormitory in Wolverhampton, England, that was built in 2010 in less than 12 months.

In New York City, the School Construction Authority has used modular technology to build classrooms, and the Capsys Corporation, a modular builder based at the Brooklyn Navy Yard, has built prefabricated steel-frame housing up to seven stories tall in Brooklyn and on Long Island.

Mr. Ratner said 60 percent of the construction would take place in a factory, where an estimated 190 workers would assemble roughly 950 steel-frame modules, each 14 feet by 35 feet, and outfit them with electric and plumbing lines, as well as with kitchen and bathroom pods. At the same time, on-site workers would build the foundation. The modules would be transported to the site, lifted into place by crane and bolted together. Steel bracing would rise with the stacked modules. The trick for developers, architects and engineers in erecting taller modular buildings has been to design an economical bracing system to protect the structure from wind shear and seismic forces.

The development once promised “upwards of 17,000 union construction jobs and over 8,000 permanent jobs.” The large number of jobs was a significant reason the state and the city agreed to provide $300 million in direct subsidies for Atlantic Yards. Mr. Ratner, a union builder, said modular construction would “probably” require the same number of workers.

Nevertheless, under current wage scales, union workers earn less in a factory than they do on-site. A carpenter, for instance, earns $85 an hour in wages and benefits at a construction site, compared with $35 in a factory setting.