House additions and room additions are valuable investments whether your home is large or small. Adding rooms with features that are desirable to home buyers can increase the value of your home in addition to expanding your available storage and living space. By adding a bonus room or apartment over your garage, you can expand your living space without cluttering up your house. Only walls and a roof are needed to complete the garage since the foundation is already in place. When it's finished, you can rent it out or use it as a guest room.