This paper presents a novel system for the construction of building structures based on the use of timber-concrete-composite pieces (floors, beams and columns). Beams and floors are composed of a prefabricated lower glued laminated timber (GLT) flange glued to one or more plywood ribs that are linked to an upper concrete slab poured in situ using an efficient timber-concrete connection of holes made on the ribs. An extensive experimental campaign was carried out to validate the solution: shear tests of wood-wood and wood-plywood glue line; delamination tests of wood-wood and wood-plywood glued planes; shear tests of the timber-concrete connection with different configurations; finally, full scale four-point bending tests of simple supported beams and three point bending tests of pieces in an overhanging configuration. In order to know the performance of the system, sizing curves using the Gamma Method were developed. Results indicates a light, slender and high stiffness structural solution very suitable to be used in building construction.