Panelized systems are prefabricated components that are brought to a construction site and assembled into the finished structure. Traditional constructions are often subjected to termite attack, mold buildups and have poor penetration resistance against wind-borne debris. To overcome these problems, a new type of composite structural insulated panel (CSIP) was developed and is analyzed in this study for structural floor applications. The concept of the panel is based on the theory of sandwich construction. The proposed composite panel is made of low cost orthotropic thermoplastic glass/polypropylene (glass-PP) laminate as a facesheet and expanded polystyrene foam (EPS) as a core. Full scale experimental testing was conducted to study the flexural behavior of the CSIP floor member. CSIP floor panels failed due to facesheet/core debonding. Analytical modeling was further presented to predict the interfacial tensile stress at the core/facesheet interface, critical wrinkling stress, flexural strength and deflections for structural CSIP floor panels. The experimental results were validated using the proposed models and were in good agreement. © 2011 VSP.