Simpson first established his practice in 1813 at his old childhood home at 15 Guestrow. He later moved to premises at 130 Union Street, where in 1826 he lost his entire archive of drawings in a fire which destroyed the building, forcing him to move his office to 8 Belmont Street and later to 22 Crown Street - where the former Post Office building now stands - before later moving to live at 15 Bon Accord Street and practicing from his office at 1 Bon Accord Street.

Simpson began his work at a time when wealthy country landowners were