Outbuilding House Plans: An outbuilding is defined as a building (a stable, woodshed, guest house, etc.) separate from, but accessible to, a main house. Because outbuildings have their own entrance and separate sleeping and living areas, they are easily adapted for use as an office or an apartment for an older child or in-law. Examples of the outbuilding house plans you’ll find in our collection include studio apartments, garages with studios, guest houses and office buildings.