Abstract: Building frame units and building structures using such frame units as load-bearing wall sections or wall panels are disclosed. The frame units comprise hollow metal sections providing longitudinal frame members, end frame members and intermediate pillar frame members interconnected to form a rectangular skeletal frame. The top and bottom longitudinal frame members and the intermediate pillars are each composed of a pair of flanged channel sections assembled mouth-to-mouth and connected by C-cleats. The end frame members are each formed by a single flanged channel section having its open mouth presented outwardly. At least some frame units incorporate fittings such as windows and doors, but all residual spaces between adjacent frame members are closed by a sheet-like infill of plastics foam material providing a sealing and insulating barrier.