The two-story junior addition is 8-7/8" wide by 11-1/8" deep by 21-1/2 high addition with two rooms and rooftop balcony. Precision workmanship engineered parts pre-cut to really work. Sturdy construction features 3/8" thick milled MDF clapboard exterior walls and grooved sidewalls .for easy, one-step assembly, guaranteed fit and durability. Kit includes step-by-step instructions with detailed drawings. Can be built for either left or right side giving you the option of installing additions on both sides of the Alison Jr. back open dollhouse