A Hingham developer hopes to put up a new residential building behind Fox Hall on Columbia Road at Arion Street that would include an upgrade for occupants of 15 single-room-occupancy (SRO) units in the current building — their own studio apartments.

In a letter of intent filed with the Boston Planning and Development Agency (BPDA), Mike Rooney’s JLCD Development said the project would include construction of a four-to-six story building on what is now a parking lot behind Fox Hall, which dates to the late 1800s.

Current SRO residents would get to stay in their existing units until that building is finished, at which point they would be offered studios there, according to the letter from JLCD’s lawyer.

The company would then renovate Fox Hall’s upper floors, while letting existing ground-floor commercial tenants stay in place.

All of the units in the new complex would be marketed to people making between 30 and 100 percent of the Boston area median income. The new complex would have 24 parking spaces. The letter signals that JLCD expects to file more detailed plans soon.