Hochtief’s US subsidiary Turner Construction has won a $399m contract to expand C Concourse at Seattle-Tacoma International Airport (SEA).

Starting next year Turner will nearly triple the concourse’s floor area from 80,000 sq ft to 226,000 sq ft by adding four floors to the existing three.

Operator Port of Seattle said the project entailed “literally raising the roof” because SEA was one of the most space-constrained airports in the US given the number of passengers it handles.

Designed by The Miller Hull Partnership and Woods Bagot, the expansion adds dining, retail, seating, an interfaith prayer meditation room, and an airfield observatory.

It aims for LEED v4 Silver certification with a rooftop PV array, reduced embodied carbon, electrochromic glazing, and biophilic design elements.

“We understand the importance of this project and the difference we can make by implementing sustainable building strategies into the expansion of this terminal,” said Bill Ketcham, Turner’s general manager.

Work is expected to finish in 2027.