The Suffolk School Board voted unanimously to approve a two-story addition to increase capacity at Northern Shores Elementary School during its Thursday evening meeting.

The addition will add 20 additional classrooms for a net gain of 18 classrooms, and this will create a total of 450 new seats.

The project will cost between $11.4 and $12.2 million, school officials estimate.

Some of those new seats will be filled with students from the two classrooms they lose in the remodel and students from the mobile units. These students will fill 175 of the new seats, which leaves Northern Shores 275 new seats after the addition is completed.

“It behooves us to address this as much as we can, and we need to look at how large we actually want an elementary school,” said Superintendent Dr. Deran Whitney.

Whitney brought forth two proposals — a one-story addition and a two-story addition — for the School Board to choose.

The School Board decided to go with the two-story addition, because it added more seats and was more cost effective.

“It is less per student, and you have a larger capacity in the same space,” said School Board member Linda Bouchard.

“The two-story one is more practical than the one-story. It is much more reasonable with the money than the one-story one,” said School Board member Michael Debranksi.

The one-story proposal would have added 17 classrooms for a net gain of 15 classrooms, and it would have added only 375 new seats.

The one-story proposal would cost approximately $32.7 million over three years, almost $3 million less than the two-story proposal.

The approved proposal was more costly because stairways, hallways and an elevator had to be added for a second story.

Both proposals added more than just classrooms to Northern Shores. Each proposal showed additional space for resource rooms, a teacher workroom and additional cafeteria space.

The cafeteria space would be on the opposite side of the kitchen as a separate space, according to the renderings provided by RRMM Architects.

Northern Shores is continuing to see growth in its student population due to an increase in home development in the northern end of the city. According to Whitney, Northern Shores is seeing anywhere between 40 to 50 additional students each year, and he doesn’t believe it will slow down.

“We have worked with the city and know that about 1,000 homes have been approved in the Northern Shores area,” Whitney said. “That doesn’t mean they will happen soon, and we don’t know what types of homes they will be.”