Exterior, Flat RoofLine, Prefab Building Type, Metal Siding Material, House Building Type, and Cabin Building Type The three-bedroom, two-bathroom cabin has a communal space with a custom Baltic Birch bookshelf, and a bench by the window where the owners can look out to the surrounding wilderness, and fern meadow.  Photo 9 of 14 in 7 Efficient Prefabs That Prove the Power of Modular Design