A building structure for plant nursery or like buildings including a pair of side frame assemblies, each defined by an elongated gutter member supported at an elevated attitude by a plurality of upstanding supports. Brackets are disposed between the supports and the gutter member, the brackets including opposite side flanges disposed adjacent opposite sides of the gutter member to stiffen same. Straps span the gutter and connect the sides thereof together to resist splaying and thus deflection of the gutter under wind loading. The building structure includes a roof frame formed of a plurality of arcuate roof frame members which are supported in opposite sockets secured to the side flanges of the brackets.