CHAPEL HILL - Projected elementary school enrollment could temporarily halt residential development in the Chapel Hill-Carrboro school district in two years.

The school system signs off on new housing plans under the Schools Adequate Public Facilities Ordinance (SAPFO), created in 2003.

Developers must get a Certificate of Adequate Public Schools confirming that the Chapel Hill-Carrboro City Schools will have enough classroom space to handle the extra children that new housing generates.

When projected new students exceed limits - 105 percent of elementary school capacity, 107 percent of middle school capacity and 110 percent of high school capacity - the school system has the authority to deny certificates.

That could happen in 2013-14 when elementary school enrollment is projected to reach 106 percent of capacity, or 51 students over the limit.

"This is a big deal, I think," school board member Mike Kelley said at the last school board meeting. "This is at the level where it's going to happen."

The school board plans to send a letter to the county and towns about the situation.

The county is aware of the situation, school board Chairwoman Jamezetta Bedford and County Manager Frank Clifton said last week. It came up when the county commissioners decided to delay construction of the district's next elementary school this fiscal year to save money.

Instead of starting on the $21.1 million school, the county provided only $500,000 to demolish existing buildings on the future Northside elementary school site.

The county wanted to avoid a tax increase, Clifton said Friday. It's also close to its recommended debt limit, he said.

But mostly, school enrollment and housing in general is not growing in the sluggish economy, Clifton said. The new school had already been delayed from when city school officials originally said they needed it, he said.

Overall school enrollment growth has slowed, but the Chapel Hill-Carrboro district is still seeing gains at the elementary level.

The school system will get close to the limit in the 2012-13 school year, when it's projected to fall just 18 students shy of the 105 percent cap, said Todd LoFrese, assistant superintendent for support services. The only way to avoid the problem, he said, would be for the county to provide at least $5 million this fiscal year so the school system could bid the project this fall and start construction by March. Construction will take roughly 18 months.

But Clifton said he doesn't see why the county, towns and school system could just agree to waive the SAPFO requirements in 2013-14, providing a new school is in the pipeline.

LoFrese said it's too early to say what school leaders might do.

"I do think it's possible all the parties could reach a resolution," LoFrese said. "But I'd need to get a lot more information before I could answer that question. There are just a lot of variables."

It's possible the issue could come up even sooner than 2013-14, for example, if a formal application for a massive development like Obey Creek comes in to Chapel Hill, he said. Obey Creek is a planned mixed-use development with 1,200 dwelling units proposed for U.S. 15-501 across from Southern Village.

The developers of Obey Creek have submitted a concept plan, an informal first step in the town's development review process. Planning Director J.B. Culpepper said the town does not consider that an "active" project yet.