Adding square footage with a room addition is one of the most popular home renovation projects. With the proper design and construction, this can make a big difference in how valuable your home is. Room additions vary greatly in terms of complexity and price, with overall cost being largely determined by the purpose of the room addition (kitchen, bathroom, office, bedroom) and the extent of the renovation. The purpose contributes to the cost quite a bit due to the cabinetry, plumbing, and electrical costs associated with a project like a kitchen addition.