A crew was rigging down a dog house with a 100 ton crane that was subcontracted for the move. After they had removed two pins from the sub floor of the doghouse and the third one was in the process of being removed, the Crane Operator decided he wanted to change out the slings. Without any warning or authorization, the Operator loosened the slings that sustained the dog house on the right side. When the third pin was removed the dog house fell. No one was injured but the equipment was damaged.