The Chiltern Lifestyle Centre in Amersham will have sports facilities, including swimming pool, gym rooms and squash courts, as well as a library and a community centre.
BAM is currently operating under a pre-construction agreement while finalising the contract with Chiltern District Council. Work on site is set to start towards the end of November, for a grand opening before the end of 2021.
The current 1960s leisure facilities in Amersham will be demolished and Amersham library has been temporarily re-located.
BAM construction director Mick Kelly said: “These are important changes for local people and we fully appreciate the need to go about our work considerately and respectfully. How we build has always been as important to BAM as what we build.
“We’ll bring our expertise in creating leisure sector developments to this scheme that will transform the facilities for people here.”