A modular construction for solariums and like structures, provides prefabricated glazed panels and interlocking joint assemblies which are easily assembled in the field without need for tools or other equipment. The panels are used for the construction of walls and ceilings, and are formed of a transparent sheet (preferably double pane glass, for its superior thermal efficiency) with a peripheral frame. The frame and joint material is preferably ultra high density polyvinyl chloride plastic material, although other materials may be used. A steel plate may be installed within the joints for additional structural strength. The construction places the transparent panels substantially adjacent the outer edges of the frame members and joints to reduce the likelihood of protruding panel edges serving as traps for water and/or debris. Preferably, the frame members are formed as hollow extrusions with plural longitudinal cavities therein, both to reduce weight and also to provide conduits for electrical wiring and/or plumbing, if desired.