The project was originally expected to start last summer, but the academy said Monday it was pushed back while the school found a contractor with experience in renovating historic buildings.
The restoration includes replacing the chapel’s aluminum skin, removing and cleaning 24,000 stained-glass tiles, stiffening the steel superstructure and adding a water barrier.
The academy says the chapel has leaked since it was built and previous repairs failed.
The school said last year the restoration was expected to cost between $58 million and $68 million.
The chapel, a National Historic Landmark, is a striking, triangular-shaped structure that stands 150 feet tall.