Abstract: A very strong lightweight modular composite concrete and steel floor that can be attached to; a light steel carrier for transportation, a foundation for a single story structure, or a light steel ceiling frame for a multistory ceiling/floor assembly, that creates a compound structure that is substantially stronger than the sum of the strength of the individual components. The thin upper concrete plane acting as the compression flange is connected by shear connectors to a pair of web members which are connected to metal chords acting as the tension flanges to create a double “T”. This in turn can be connected to a pair of web member/metal flange structures creating an even taller stronger double “T” for; the carrier, or the long spanning ceiling/floor assembly of a multistory building. The module is delivered to the site, unbolted from the carrier and set on the foundation or connected to the lower story module.