Appointed using the SEWSCAP framework, it will increase the Penywaun school’s capacity by 187 places for the 2022/23 academic year.
The project’s scope includes construction of a new eight-classroom block, which will include community rooms, along with school drama and music facilities.
There will also be a new school reception, sports hall, fitness suite and changing rooms, along with a 45-space parking area and cycle store.
Working in a live environment, Willmott Dixon will also demolish the current caretaker’s house and remove the school’s temporary classrooms.
Minimising disruption to the school day is a key part of the project, with the majority of the heavy machinery to be delivered during the school’s summer holidays.
Rhondda Cynon Taf Council’s Cabinet Member for the Welsh Language, Councillor Geraint Hopkins, said: “The council is delighted to welcome Willmott Dixon on board for this project. The works will deliver a significant upgrade to the school’s current facilities – including a brand new classroom block, school reception, sports hall and extra parking provision.