NORWOOD PARK — Oriole Park Elementary School's new two-story, $20 million annex will include a multipurpose room — but not a gym, as requested by parents and school officials, according to plans unveiled by city officials.

Oriole Park Principal Tim Riff said he was nevertheless pleased with the design for the annex, which will also include 15 classrooms, a computer lab, a science lab, a library, art room and administrative offices.

"I would have loved a full-size gym, but it wasn't in the cards," Riff said after the plans were shown to parents and teachers Monday night. "It will definitely ease the space crunch."

Heather Cherone explains why students won't get a much needed gym at their expanding school:

Although the main building at 5424 N. Oketo Ave. was meant for 390 students, 661 students are enrolled at Oriole Park. That gives the school a utilization rate of 169 percent, one of the highest in the city, according to CPS data.

But Oriole Park has an eight-classroom modular building. The school also leases two classrooms from St. James Church, which is two blocks away, for the school's two pre-kindergarten classrooms.

That gives the school an adjusted utilization rate of 110 percent, which is not considered overcrowded, according to data provided by CPS.

Construction of the annex, which will nearly double the size of the school, is expected to begin in six weeks, and be completed in time for the first day of school in September 2015, said Public Building Commission Executive Director Erin Lavin Cabonargi.

The Public Building Commission board approved a contract worth $11.8 million Thursday with IHC Construction Corp. to build the annex and renovate the main building.

The budget for the annex was not big enough to include a gymnasium, Lavin Cabonargi said.

School leaders and parents pushed for the multipurpose room to be as big as possible, Riff said.

"We didn't get exactly what we wanted," Riff said.

The multipurpose room, which will serve as the school's new lunchroom and include kitchen and food service facilities, will be big enough to accommodate physical education classes and school assemblies, Lavin Cabonargi said.

"We pushed for as big a space as we could get," Riff said.

Matt Malarski, who will have three children at the Norwood Park school next year, said he was disappointed that the multipurpose room was not bigger.

"It is just too small," Malarski said. "It is fortunate that we are getting an annex, but you always want a little more."

The building will have a steel frame with a brick exterior, Lavin Cabonargi said. The building will be designed to allow as much natural light as possible into classrooms and hallways, she added.

The annex will also have a beefed-up roof and thicker-than-average windows to block out the noise of jets traveling to and from O'Hare International Airport, Lavin Cabonargi said.

The administrative offices in the 80-year-old main building will be turned into a classroom and the old lunchroom will be turned into an art room once the annex is complete, Lavin Cabonargi said.

Plans also call for a new playground with equipment designed for both younger and older students and a new turf field to replace the grass behind the school, which gets soggy in rainstorms, Lavin Cabonargi said.

In addition, a new crosswalk and traffic signs will be installed at Balmoral Avenue in front of the annex to help students get to school safely, Lavin Cabonargi said.

The first floor of the annex will include five pre-kindergarten and kindergarten classrooms. The second floor will feature a library, a computer lab, a science lab and 10 classrooms, probably for the middle-school students, Riff said.

Enrollment at the school, which is ranked among the city's best, is expected to grow for the next several years, Riff said.