A Boston development company that specializes in emerging residential markets is planning a 28-unit apartment complex at 1065 Tremont St. in Roxbury.

Urban Core Development is partnering with Boston Real Estate Collaborative on the plans for a 6-story, 31,500-square-foot expansion and renovation project. All but four of the units would be rented at market rate.

The developers acquired the property in 2014 and completed the first phase, consisting of 16 apartments managed by BREC and a commercial space, in April.

“The redevelopment of the underutilized and structurally failing single-story commercial property into a 6-story, 16-unit residential market rate rental building has added energy and vitality to the rapidly improving Tremont Street corridor,” wrote V. William Avanessian, founding partner of Boston Real Estate Collaborative, in a notification form submitted to the Boston Planning and Development Agency.

The next phase, also designed by Monte French Design Associates, would restore a single-family commercial property and build a 6-story addition. Units would range from 370 to 1,630 square feet with a mix of one to four bedrooms. No on-site parking is planned.

The project is subject to a small project review by the BPDA.

BREC and UCD previously collaborated on the redevelopment of 1902-1904 Washington St., the formerly-abandoned Alonzo Dexter Residence, into a nine-unit residential building.