A granny flat in Brisbane costs between $200,000 and $450,000 total for design, approvals, site works, construction and service connections. Architectural fees are $5,000–$12,000 . Brisbane City Council allows secondary dwellings up to 80 square metres on most residential lots. A Development Application is almost always required, taking 8–12 weeks for approval. Total cost $200K – $450K Architect fees $5K – $12K Max size (BCC) 80m² DA timeline 8–12 weeks The short answer For