Whether you are adding a second story on top of an existing garage, or building a two-story ADU, the advantages are multifold. A two story structure has a more compact footprint. By vertically stacking the living spaces, a two-story ADU can accommodate multiple bedrooms, bathrooms, and shared spaces without expanding the building’s ground footprint. In addition, a two-story ADU presents an opportunity for greater privacy and separation between living areas. It allows you to designate different floors for specific functions, such as bedrooms on the upper level and shared spaces on the lower level.