FMC Corp. plans to move this weekend into its still-under-construction University City headquarters tower, among the most prominent of the recent building projects that are reshaping the city's skyline.

The chemicals giant will be the first tenant in the glass tower that will bear its name near 30th Street Station, where it is to occupy 250,000 square feet over nine floors, communications chief Ken Gedaka said in an interview on Thursday.

The move was timed to beat the expiration of its lease at its current home, the BNY Mellon Center tower at 1735 Market St., which it had occupied since 1991. That building's owner is considering an elevated deck and other new amenities to help revive occupancy levels after FMC's departure.

The FMC Tower, due for completion this fall, will stand 49 stories, comprising 622,000 square feet of office space under 18 floors of residential units. Developer Brandywine Realty Trust's other nearby projects include the Cira Centre and Evo towers.

Crews are working on the FMC building's 47th story, its highest floor for occupants, Brandywine chief executive Jerry Sweeney said in an email. The lower office section is complete, so ongoing construction should pose no special challenges for FMC's 550 workers, he said.

Staff will enter the structure through a sheltered pathway to protect them from any falling items connected to construction, Gedaka said. "It's really an exciting space to be in, even though parts are still being finished," he said.

FMC is to be joined in the tower by office tenants including the University of Pennsylvania, which will occupy 100,000 square feet of space, and the former Philadelphia Stock Exchange - now part of the Nasdaq Stock Market - which will lease 75,000 feet.

The chemical company's departure will leave the 1.3 million-square-foot BNY Mellon tower, about a mile away, with 445,000 feet of vacant space, according to the building's owner, Equity Commonwealth. Also contributing to the 54-story building's vacant space was the downsizing of its namesake tenant, Bank of New York Mellon, which let a lease for 184,000 square feet lapse last year.

Equity Commonwealth's chief operating officer, David Weinberg, told analysts during a conference call on May 4 that the company was "looking at adding a tenant lounge, conference center, and a rooftop deck" at the building. A spokeswoman for the Chicago-based real estate trust did not return calls seeking additional details about the renovation plans.

The deck would likely overlook Market Street from the broad five-story base that supports the building's narrower remaining floors, according to Mitch Marcus, a managing director at commercial real estate services firm JLL who has seen plans for the site.

The lounge and conference rooms would also be on the fifth floor, inside the building leading to the deck, he said.

The outdoor space would be a unique offering in Philadelphia's western Center City skyscraper district, but such amenities have been successfully deployed by office-tower landlords in other cities, Marcus said.

"It would give them a competitive advantage," he said. "I haven't seen it done here to that extent and that size."

215-854-2615 @jacobadelman