Suffolk Manages ‘Sky Mat’ Pour at Winthrop Center

Winthrop Center sky mat

Boston – In a first for the city of Boston, Suffolk recently managed the pour of a 20-million-pound “transfer mat” (aka “sky mat”) halfway up to the eventual top of Winthrop Center, a 52-story tower slated to be the fourth-tallest building in the city of Boston.

The mat, which required 1,200 tons of rebar and nine levels of shoring compared to the typical five, had to be kept in place for 21 days. The purpose of the slab, located 350 feet off the ground, is to separate the office and residential components of the tower, which require different layouts and structural elements.

The office floors will have open floor plans spanning 45 feet, with few walls and columns on the floors to support the building’s structure. The residential floors of the tower will be denser with residential units and columns on the inside. The contrasting uses of the tower presented a unique challenge: The team needed to find a way to bear and transfer the weight to the lower, more spaced-out perimeter columns, and eventually the ground. The transfer mat will help create column-free, unobstructed views of the outdoors, which promotes the overall healthy building design strategy.

Once completed, the 691-foot Winthrop Center will deliver 812,000sf of Global Class A office space and 572,000sf of residential space comprising 321 residences, and is integrating health and wellness, productivity and social engagement, and technology and sustainability into its design.

“The pour of the transfer mat was carried out flawlessly, thanks to the careful planning and execution by the entire project team,” said Suffolk project executive, John Newhall.