Abstract: An adjustable support structure is used to support various types of roofs, such as flat, single slope and double slope roofs. The support structure includes a channel shaped post, a load beam assembly connected to the post at about its uppermost end, an adjustable bracket adjustably secured to the load beam assembly, and a purlin secured to the adjustable bracket, at a generally angular position relative to the load beam assembly, for supporting the roof. The adjustable bracket includes an upwardly oriented generally U-shaped seat which is secured to a downwardly oriented generally U-shaped saddle, such that the saddle is mounted snugly across the load beam assembly, and is adjustably connected thereto. An extender is adjustably secured to the post and to the load beam assembly. The extender includes a generally U-shaped seat, which supports; it is connected to the load beam assembly, such that the extender seat can be adjustably connected to the load beam assembly along the horizontal direction.