320 Summer St./Image courtesy of Google

A pair of vacant office buildings in Downtown Crossing and Fort Point are joining the queue of residential conversions in Boston.

Developer William Thibeault submitted an application for 11 and 15-17 Avenue de Lafayette to be converted into 74 apartments on the upper floors. The 6-story building totals 54,475 square feet. All but five of the apartments would be studios.

Thibeault Development has completed conversion projects in the Downtown Crossing and Financial District neighborhoods.

In Fort Point, developer Fan Du plans to create 139 apartments renting for an estimated $2,220 to $3,872 at 320 Summer St., a 130,660-square-foot office building. The conversion will include a 425-square-foot roof deck and amenity space.

Both developers said they will finance the projects privately. The estimated $66.5 million Fort Point project includes $26 million in acquisition costs.

Approval under the program entitles developers to a 75 percent property tax abatement for 29 years. Applications to participate now expire at the end of 2026, following a 12-month extension approved by the city in December.

Large-scale projects submitted since the beginning of the year include Synergy’s 255-unit project at 294 Washington St. and developer Patrick Mahoney’s plans for 171 apartments at 50 Congress St.

Nearly 1,650 housing units have been submitted under the program.