The outbuilding comprises three different parts - a cowshed, a stable for sheep and other animals with a hay loft above. The central building, which is the oldest part, housed the sheep. This part was gone when the restoration of Strømsør was started. It was rebuilt in 1992. The other part of the building is from the 19th century. The barn comprises the northern part of the outbuilding. This part of the building was made with cogging joints

the corners are filled with chinking and daubing. While the loft is made using stave construction - with strong slanting buttresses and trusses. The barn section is clad with vertical panelling.

The stable is a two-storied timber structure with chinking and daubing in the corners and a sod covered purlin roof. There are stalls on the bottom storey and a hayloft above. In front of the stable is a corridor made using stave construction and covered with horizontal panelling. Here there is a stable door that is divided into two. Both the stable and the barn have a walkway/bridge entrance on the backside of the building.