A modular seating system in which at least two supporting elements serve a dual function including that of providing a seat support and an additional function. Each such supporting element includes a hollow shape having vertical supporting walls and is formed from a cured organic polymer reinforced by an inert fibrous filler such as glass fibers. The elements support a seating component that includes a beam provided with a first plate affixed at each end in a plane perpendicular to the axis of the beam. The beam is affixed at each end and suspended by one of the supporting elements. Mechanical fasteners extend through the plates and through a vertical wall of said hollow shapes. A second reinforcing plate is provided on the inside of said vertical wall, and the mechanical fasteners also extend through the second reinforcing plates, causing the first and second plates to apply compressive force on the supporting wall. One or more seating units are attached to and supported by the beam. The supporting components can act both as a seat support and a table, planter or kiosk.