Mattress assemblies including static and adjustable mattress foundations generally include a foundation frame including side frame members and transverse frame members attached at respective ends by a corner bracket at each of the respective ends to define a generally rectangular shape. An adjustable support leg coupled to each one of the corner brackets for automatically elevating the foundation frame relative to ground. The adjustable support leg can include an outer tubular member fastened to an interior facing portion of the corner bracket including an end cap, wherein the end cap includes an aperture. A motorized linear actuator can be coupled to the outer tubular member, which can include a motor and an extendible portion coupled to the motor. The extendible portion is configured to selectively retract from and extend through the end cap to change the elevation of the foundation frame relative to ground.