This paper examines a new and very promising concept for prefabricated timber-concrete-composite floors (TCC-floors), were the heavy normal weight concrete is replaced by a lightweight concrete (LC) with a density of about 17 kN/m³. Investigations into the connections between lightweight concrete and timber indicate that the performances of the existing connection types are unsatisfactory if combined with lightweight concrete. Therefore, a new connection method is proposed, adhesively bonding the lightweight concrete with the timber by means of a filled epoxy resin. Different ways of manufacturing the bonded timber-lightweight concrete-composite beams (TLCC-beams) are investigated in a research project at the Technische Universität Berlin, to examine the differences in their structural performances. Most promising are the test results for TLLC-beams, fabricated with a wet-in-wet bonding method.