A major expansion of South Portland High School is taking shape and will reach a milestone Friday when the top structural beam is lifted into place. The $47.3 million project includes a new learning commons, cafeteria and lecture hall. Construction began in June and is expected to end by spring 2015.

Superintendent Suzanne Godin said Thursday that the project is on budget and about a week behind schedule. “The project is going up within, in many cases, inches of our classroom spaces,” she said.

Godin said it is hard for passers-by to miss the changes on campus, including two three-story classroom spaces and the distinctive new cafeteria with its rounded roof.

In November 2010, South Portland residents approved a $41.5 million bond to renovate and expand the high school. The total cost of the project is $47.3 million, to be covered by the city’s taxpayers because no state aid was available.

Friday’s “topping off” ceremony will begin at 11 a.m. Members of the school board, the building committee, the City Council and the Student Senate will sign the beam before it is lifted into place.