The main building is most likely built according to The Norwegian Church Department’s guidance drawing of 1835 by architect H.D.F. Linstow, modified by J.L.B. Svendrup. The drawing is often called “The Sverdrup-Linstow plan”. Brønnøy Vicarage has a smaller footprint than the drawing. The floor plan is slightly different, and the attic has been expanded in order to include several bedrooms.

Originally there were two back entrances, one for the offices and one for the kitchen. The main entrance was moved to the east side. It received its present form in the 1990s with an empire door and a roof with two columns.