A vehicle having a bottom frame including a plurality of rails includes a floor structure defined by a plurality of longitudinally extending flooring planks extending along at least part of the length of the vehicle body and arranged side by side at a coupling rail or overlapping joint so as to collectively span between the side walls. The planks are molded for example by pultrusion or vacuum resin infusion from a composite having an upper skin and a lower skin and an intervening core material layer. The planks can be easily provided at required different lengths including a center and side planks installed while standing on the center plank. The planks can be trimmed to any length for vehicles of varying lengths.