CAMDEN, Maine — The School Administrative District 28 board gave its unanimous backing Thursday to a new two-story, 82,000-square-foot middle school on the grounds of the existing middle school in Camden.

The full board supported the new school over other options that included renovations of existing facilities or renovations and additions.

The ballpark cost of a new school is $23 million, said Superintendent Elaine Nutter. The school would serve the approximately 375 fifth-through-eighth-grade students in Camden and Rockport.

The architectural/engineering firm of Oak Point Associates of Biddeford, which the board hired last July, will develop more detailed plans and will present them to the board and public in June.

The superintendent said she expected the earliest a referendum would be held to ask voters whether they want to borrow money for the new school would be 2015. If the board and voters back the project, students could be in the new school in time for the 2018-2019 academic year.

The two towns will pay the full cost of the project because the district is a minimum receiving school in terms of state aid.

About 40-plus residents have turned out for each of three public forums at which school officials explained the options, Nutter said.

The superintendent said while the district considered putting the new school on Route 90 in Rockport near where Camden Hills Regional High School and Camden-Rockport Elementary School are located, there was not sufficient land available. In addition, she said there was strong public sentiment to leave the middle school in Camden because it is the last public school in the town.

Last week’s meeting was the third public forum on options for how to address space needs for a middle school.

The original Mary E. Taylor Middle School was built in 1925 on Knowlton Street and has undergone expansions since then. The district maintains that the current building, covering 122,000 square feet, is inefficient and costly in terms of use, maintenance and operation.

The other options would have been more expensive and would have met the district’s goals, including educational function, parking and traffic flow.

The current bus barn building adjacent to the school is occupied by administrative offices, the alternative education program known as the Zenith Programs, and the adult education program. Those programs could lease space in the new school, she said.