Abstract: A closure assembly and a method of installing the closure assembly are provided. A insertion opening is formed in water resistant barrier covering a rough opening that generally corresponds to a perimeter of the rough opening. A drainage system including a channel assembly is installed on a sill surface of the rough opening. The closure assembly is inserted into the rough opening and temporarily secured to the structure. At least one shim carried on the closure assembly is adjusted to level the closure assembly in the rough opening. A sealing member attached to the closure assembly is engaged with the water resistant barrier. A foam material is delivered into at least a portion of a space between perimeter edge surfaces of the closure assembly and inner surfaces of the rough opening to permanently secure the closure assembly within the rough opening.