The lecture, titled 'Defining the Void', will be given by Patrick Richard and Caryl Stephen at Henry Tudor House on May 22.
Group chairman Michael Cruise said: "Our aim is to promote architecture and design, connecting professionals, students and enthusiasts throughout the county."
The series, which included three lectures over March, April and May, hopes to encourage young people interested in a career in architecture, as well as members of the public who have an interest.
The society is a local branch of the Royal Institute of British Architects.
Tickets will be available in equal number to architects and non-architects alike for £3 on the door and guests should arrive at 6.30pm for a 7pm start.