Complex sentence: Beside the additions, there were also changes to the inside of the building, which included moving the Guidance office from a small room at the end of the hallway to a large, multi-room office, about 1.5 times the size of a normal classrooms.
Split into simpler sentences: Beside the additions, there were also changes to the inside of the building. Many changes occured inside as well, including moving the Guidance office from a small room at the end of the hallway to a large, multi-room office, about 1.5 times the size of a normal classrooms.