Seaport District’s 350 Summer Street could shift from mostly residential to mostly office

A large part of the Seaport District’s Seaport Square development might shift from housing to office to host yet another life sciences hub in the Boston region.

Seaport Square developer WS Development has filed a request with the Boston Planning and Development Agency to make the proposed 350 Summer Street primarily office space rather than residential. Per the request, the building would be comprised of “approximately 384,000 square feet of office and/or research and development uses” and about 38,000 square feet of restaurant, entertainment, and retail usage.

The building had been slated to host 350,000 square feet of residential and 72,000 square feet of restaurant-entertainment-retail.

What’s more, it appears that WS Development has a tenant lined up should the city okay its conversion of 350 Summer to mostly office use. Foundation Medicine, a Cambridge-based life sciences firm that has already leased 580,000 square feet at WS’ under-construction 400 Summer for its new headquaters, intends to take space in 350 Summer as well, per the Globe’s Tim Logan.

It will be the latest major move into new real estate by a life sciences firm in the Boston region. New or proposed projects from Somerville to Watertown to Somerville again to different parts of Boston, including South Boston and Allston, are seeking to draw or have drawn biotech firms. No surprise, given the industry’s presence regionally—but still notable given that all of these projects have advanced or been proposed in just the past 12 months.

The shift at 350 Summer, however, has raised concerns about the loss of residential units in a Seaport District—and a Boston—that needs housing of all kinds. WS said in its request, however, that it would still build the approximately 3,200 units it originally proposed for Seaport Square, “in part by shifting the mix of unit types to include more smaller, lower-priced units and fewer large luxury units.

“This shift also reflects the need for a greater density of more affordable homes citywide,” the developer said in its request, “and will better serve the employment base in the Seaport District.” Stay tuned.