A portable building structure (10) comprising first and second building segments (12a, 12b), each segment comprising a base structure (18), a wall structure (20, 22) and a roof structure (16) and being configured to define a row of animal pens (34). The base structure provides a tank (42) beneath each pen. The first and second building segments comprise individually portable units. To install the structure the first and second building segments are constructed off site and individually transported on site. The building segments are then located side-by-side but spaced apart and a mid-segment (14) is constructed to join the building segments together.
