Abstract: A ceiling includes arched panels supported by box type beams which are adjustable in width. The sides of the beams are provided with inclined grooves in which the edges of the panels are received. The panels are flexible and tend to unflex to a flat shape, thereby retaining their edges in the beam grooves. The ceiling beams include beam members which are spaced apart by adjustable spacer brackets. A bottom panel of each beam may be opened to gain access to the beam for interior adjustment of the brackets. Light fixtures are mounted within the beams above translucent panels incorporated in the bottom beam panels. Curved wall panels supported by wall beams may be employed in combination with the ceiling. In an alternative form of the invention, upright box type beams support curved wall panels and partitions.