Interior Design Interior design is the process of shaping the experience of interior space, through the manipulation of spatial volume as well as surface treatment. Not to be confused with interior decoration, interior design draws on aspects of environmental psychology, architecture, product design and furniture design in addition to traditional decoration. Designers often specialize in one or more specific types of interior design. Some designers specialize in only residential or commercial (or, contract) projects, but many designers do both residential and commercial projects of various kinds.