Responding to strong demand for office space in Boston’s Fort Point, a developer has begun construction of a glass-wrapped 2-story addition atop 22 Boston Wharf Road.

Bentall Kennedy, the real estate manager for landlord Multi-Employer Property Trust, is overseeing construction of two floors of open-format office space totaling 54,712 square feet. Another 55,000 square feet is available on the seventh and eighth floors in space previously occupied by TRO Boston and Red Thread.

The space will be ready for tenants to begin interior fitouts as soon as this fall, said David Fitzgerald, a partner at CBRE/New England which is representing ownership.

“We hear from the tenants who are looking at the Seaport District market that they want to be in tomorrow,” Fitzgerald said. “It’s unusual in Boston, where we’re used to tenants looking three years in advance.”

The seventh and eighth floors are being gut renovated with windows installed on the north side of the building overlooking Q Park, which is part of the master-planned Seaport Square development.

The 28,000-square-foot floor plates, with only four columns, lend themselves to open-format office space. Fitzgerald said asking rents are in the $60s per square foot on a gross basis.

The office space sits atop a 580-space parking garage which is being retained. A 2,000-square-foot retail space is available on the ground floor.

MEPT acquired 22 Boston Wharf Road in October 2015  for $86.5 million, part of a four-building Fort Point portfolio sold by Boston-based Berkeley Investments for $162.5 million.