A luminaire assembly comprises a first luminaire structure and a second luminaire structure, each configured for positioning in an illuminatable position on an enclosure surface. Each of the first and second luminaire structures comprises a housing structure and an illumination structure extending outwardly from the housing structure. The illumination structure has at least one outer surface region which terminates at a longitudinal distal end region and at least one lateral edge region, wherein the respective lateral edge regions of the first and second luminaire structures are alignable to form an aligning interface therebetween. A clamp assembly is configured for clamping the adjacent lateral end regions in the aligning interface to join the first and second luminaire structures together, the clamp assembly providing at least one outer clamp surface region which is configured to be complementary with the corresponding at least one outer surface region of each of the joined first and second luminaire structures.