A tray-like modular building component adapted for filling with concrete after assembly with like components into a building frame, said tray-like modular building component comprising: a substantially rectangular frame with a pair of opposed sides and a pair of opposed ends defining an interior therebetween; a sheet mounted to said building frame and extending over said interior; a pair of beams, each mounted to said building frame along each said pair of sides respectively; and a pair of end plates, each mounted to said building frame along each said pair of ends respectively, wherein said sheet, said pair of beams and said pair of end plates together form an open-topped tray for receiving the concrete therein.