The sliding door assembly has a non-metallic frame formed of extrusions of solid cross-section and a pair of non-metallic sashes slidably disposed in the frame to move laterally between a closed position and an open position relative to frame. The floor of the sill extrusion is sloped rearwardly and longitudinally downwardly toward a notch to direct water thereto for draining out of the frame. The frame can be dropped into a commercial refrigeration cabinet and each sash is removably mounted in the frame.