BRUNSWICK, Maine — A plan to upgrade two schools could cost the town more than the $21 million originally estimated, but the total won’t be known until the school board’s March 6 facilities meeting.

“It wouldn’t surprise me if the costs were more than the $21 million,” Lyndon Keck, the principal architect working on plans for Brunswick Junior High School and Coffin Elementary School, said Tuesday.

Keck’s firm, PDT Architects, is the second firm hired by the town for the project. The $21 million estimate was from another firm that performed the first phase of the upgrade plan.

Superintendent of Schools Paul Perzanoski said the March 6 meeting, at 6 p.m. at Coffin, will be an opportunity for school board members and the public to see why it may be time to upgrade the two schools – or possibly build a new one if that costs less.

Perzanoski said a projected increase in student population was one of the original reasons for pursuing the plan in the first place, prompted in part by the closing of Jordan Acres Elementary School in 2011.

“But the main reason was that the buildings were falling apart and needed to be upgraded,” Perzanoski said. “Especially concerning was having classes in the [portable classrooms].”

Coffin has had five portable units for several years, and Perzanoski isn’t the only one who thinks they should go.

Standing on the road between Coffin’s entrance and three of the mobile classrooms, Principal Steve Ciembroniewicz explained on Monday the time constraints and safety concerns the current setup creates.

“Imagine the transition times, and you’re bundling up …,” Ciembroniewicz said while motioning to the crosswalk, where a class of small children and their teacher just crossed. “This is a big deal. This has to change. We don’t want little kiddos crossing all the time.”

Beyond increasing the safety for Coffin students and getting rid of the mobile units, Keck said Coffin and the junior high, both more than 50 years old, have structural problems that could increase the cost of the upgrade plan.

“These buildings are not terrific,” Keck told the school board at the last facilities meeting. “They were not terrific when they were built.”

The cost upgrades will be presented at the March 6 meeting in four cost options, depending on the scope of work.

While the minimum amount of work would consist of basic repairs, such as removing asbestos from beneath the floors and replacing broken toilet fixtures, another cost option would focus on adding more capacity to the schools, Keck said.

Keck said that while basic repairs would be less costly, they wouldn’t do much to increase the longevity of two buildings.

“If you do a full renovation you can say … it’s more expensive,” Keck said, “but … it’s a good investment and it will go on for another 40 years.”

Some of the work would entail updating the two buildings to modern code standards and adding insulation.

Also, the walls between the classrooms at Coffin have quarter-inch plywood, which not only allows sound to travel into other classrooms, but also makes the building more combustible, Keck previously told the school board.

At the junior high on Monday, Principal Walter Wallace demonstrated some of his building’s deficiencies.

“These are partition walls. They fold, they open up,” Wallace said, pointing at the thin exterior walls of a few classrooms. “This is not very good for sound.”

Stopping by a classroom in another part of the sixth-grade hall, Wallace pointed down at the floor.

“You can see that it slopes down,” Wallace said, explaining that several classroom floors have sunk from the hallway’s floor level. “Now you can take a marble and it will roll all the way across the floor.”

In case renovations prove too costly, Keck said he will also have cost estimates for new buildings.

Although the school board will have to decide which path to take, the final decision will be left to voters when a bond issue goes to referendum, probably in November.

Last fall, Town Manager Gary Brown estimated a 6 to 7 percent increase in property taxes if the town borrows $21 million for the school upgrade plan. That figure could increase depending on the cost options that emerge March 6.

“If there’s not support for [a bond], the buildings stay exactly the way they are and we try to keep them running,” Perzanoski said.

He said he likely will examine the costs of taking that route at one of the next school budget meetings.