The architecture arm of Bournville Village Trust has been acquired by national group Stride Treglown.
The division will be renamed Stride Treglown but will retain its office in the historic Birmingham suburb.
Founded in 1900 by George Cadbury, the trust is one of the oldest housing associations in the country and provides housing and estate management services to 8,000 homes of mixed tenure and 25,000 people in Birmingham and Telford.
Bournville Architects has designed and delivered sustainable communities in the Midlands for the trust and built a portfolio of housing, education and care projects for clients throughout the UK.
Birmingham becomes the tenth location for Stride Treglown which is headquartered in Bristol and provides architecture and town planning services.
Ian Tipton, formerly a director with Bournville Architects, will lead the new office following the undisclosed deal.
Stride Treglown chairman David Hunter said: "We are delighted to be opening our new Birmingham office with the acquisition of Bournville Architects.
"When we began the process, we took soundings from clients, consultants and colleagues in Birmingham and the Midlands region and Bournville Architects very quickly emerged as the ideal organisation.
"With a growing workload in the area, we are excited about the opportunities that the new office will open up for Stride Treglown."
Peter Roach, chief executive of Bournville Village Trust, added: "Stride Treglown is an experienced and respected practice and, by joining with the organisation, Bournville Architects will be able to share its expertise nationally as part of one of the largest practices in the UK.
"We are proud of the work that Bournville Architects has delivered for the trust, including the regeneration of the Shenley estate and our flagship care village in Birmingham, and we look forward to continuing to work with them under their new ownership."