Prefabricated plastic shed and components therefor

A rectangular shed formed from prefabricated hollow plastic members comprising side walls, end walls and a roof, said members of said end walls having upper portions which slope upwardly to a central ridge, and said roof sloping upwardly toward said central ridge, said roof members having lower ends supported by said side walls and having upper ends supported by a ridge beam assembly including a metal beam spanning between and supported by said end walls, a plastic sleeve sleeved on and supported by said metal beam and encasing said metal beam between said end walls, said sleeve having spaced depending sides, each of said depending sides of said sleeve having a longitudinal downwardly sloping roof support shelf spaced entirely below a top of said sleeve and metal beam for supporting said upper ends of said hollow roof members, said ridge beam assembly further including a ridge flashing overlying said sleeve and the upper ends of said roof members, wherein said roof supporting shelves and said plastic sleeve comprise a continuous, unitary, homogeneous element.