Residents in Sydney’s eastern suburbs have expressed concerns over a private school's $81.7 million upgrade, fearing its expansion will worsen traffic congestion in the area.

Moriah College plans to add a new three to four-storey learning facility, a new sports court complex and outdoor gardens to its Queens Park premises.

The proposed redevelopment at Moriah College. Credit:FJMT

The school also wants to increase enrolment from 1680 students to 1970, which would occur progressively over a timeframe of at least 15 years.

Victoria Lincoln, a member of the Queens Park Residents Against Moriah Expansion, said traffic through the area is already at a "gridlock".