Abstract: A modular building assembly is disclosed. The assembly consists of connecting hubs fixedly interconnected with tubular members. The hubs are each made up of one generally circular, central ring and two semi-hemispheric portions or lobes, the ring and lobes being mutually and adjustably engageable. The outer surfaces of the ring and lobes have a plurality of rounded protrusions or apertures that are adapted to engage or receive the hollow ends of the tubular members. In one embodiment, the inner ring has a central, circular aperture therethrough that can also receive a tubular member, the aperture being dimensioned to engage the outer surface of the tubular member.