A greenhouse (1) has a roof (2) including a plurality of substantiallyparallelcrossbeams (3, 3'), at least two longitudinal sections (4, 5, 24, 5') whichare mounted to thecrossbeams (3) and extend at a distance from each other in transversedirection of thecrossbeams (3), a transparent foil (6) which is mounted to the longitudinalsections (4, 5, 24, 5')at respective foil attachment locations (7) thereof so as to form a coverbetween the longitudinalsections (4, 5, 24, 5'). The roof (2) also includes a displacement mechanism(8, 8') for displacingone of the longitudinal sections (5, 5') with respect to the other (4, 24)between anon-foil-stretching position and a foil-stretching position. The distancebetween the respective foilattachment locations (7) is larger in the foil-stretching position than in thenon-foil-stretchingposition. The displacement mechanism (8, 8') can be operated and is lockableat an upper sideof the roof (2).
