Abstract: Upholstered furniture, such as an armchair or couch, that is built on a thermoformed plastic frame that replaces the wooden frame in standard furniture construction. The thermoformed frame has a horizontal base with integrally molded legs which support the chair or couch and a vertical back and sides. A plastic foam insert is generally U-shaped so that it forms the undercushion of the seat, the sides of the chair and the arms of the chair in a single piece which fits into the thermoformed frame. The plastic foam insert is made so that it interlocks with the thermoformed frame without the need for additional fasteners. A fabric slipcover, which has zipper closures for easy installation and removal, covers the frame and the plastic foam insert and holds them together as a unit. A plastic foam seat cushion and a plastic foam back cushion, each with their own fabric covers, complete the chair or couch.