Modular building structure

Disclosed herein is a modular building structure. The structure includes a modular building roof structure comprising the roof structure which includes a plurality of truss structures each having a top and a bottom and a pair of deck layers attached to and for transversely spanning the tops of the truss structures. The roof structure also includes an acoustical ceiling suspended along the bottoms of the truss structures. The building structure also includes a modular building floor structure which comprises a deck structure including an upper deck pan and a lower deck pan disposed opposite and adjacent each other to create a plurality of spaced apart support channels. In a preferred embodiment, the deck structure is oriented transverse to the support beams. The floor structure further includes a plurality of support beams for supporting the deck structure. Significantly, the deck and the acoustical ceiling define a return air plenum that provides for proper venting, distribution and circulation of air, including introduction of fresh air, throughout the modular structure. Advantageously, no separate ductwork or duct system is required with the use of the air plenum. Preferably, the structure is substantially non-combustible and mold-resistant.