Whether you're consciously aware of it or not, you are always surrounded by interior design. In every dwelling, no matter how humble or magnificent, someone had to choose the flooring and wall colors or determine the decorations and furniture placement. The practice of designing interiors for comfort and beauty is nearly as old as human habitation. Although periods and styles come and go, certain principles have remained constant over the centuries.

Interior Design Principles

Interior design follows certain principles that are common to all design specialties, but adapts them to create attractive and functional interiors. For example:

Unity refers to designing a home as a cohesive whole. Each room can display its own personality, but, together, they all look as if they belong to the same house. Using similar window treatments or one style and color of flooring throughout are examples of ways to create unity.

Focal point relates to the idea that every room should have a center of visual interest, which serves to anchor the furniture arrangement while adding personality to the room. An architectural feature such as a fireplace, bay window or built-in bookcase makes a focal point. If the room lacks such features, a focal point can be created by grouping pictures on a wall or arranging decorative objects on a sideboard, for example.

Color is a versatile tool in interior design. Color can be used to unify spaces or delineate focal points, visually improve the room's proportions, brighten a dark room or cool down a room that has a hot southern exposure. Colors affect your mood. Designers use this principle to help align the atmosphere of a room with its purpose.

Other basic interior design principles include scale and proportion, balance, rhythm and details.

Interior Design as a Profession

Unlike interior decorating, which primarily involves the decorative elements of a room and requires no formal training, interior design is a specialized profession with its own standards, requirements and credentials. Usually a bachelor's degree is needed for entry into the field, and some states require passing an exam to use the title interior designer.

Interior designers oversee the project from start to finish, including:

  • Working with the client to develop the concept
  • Drawing up plans and sourcing materials and vendors
  • Coordinating design needs with architects and builders
  • Overseeing the installation of furnishings and design elements
  • Reviewing the finished project with the client to ensure satisfaction

Interior designers must ensure that all materials and work specified in the design phase meet applicable safety and building codes. Not doing so can pose hazards, resulting in death, injury or loss of property -- and sometimes lead to legal penalties for the designer.

Interior design has various specialties, including:

  • Lighting design uses lighting installations to achieve a desired effect. In addition to home and commercial work, lighting designers may work for theatrical productions, healthcare facilities, and museums or galleries.
  • Universal design focuses on making buildings accessible to all, including those who are physically disabled. For example, universal design recommends using a lever mechanism instead of a doorknob. This makes the door easier to open for those who have limited use of their hands. It also helps anyone who enters the space carrying an armload of books or a bag of groceries.
  • Sustainable design incorporates environmentally sustainable products and principles. The goal is to design a building that efficiently uses resources such as energy and water, promotes healthy air quality and is free of toxic materials.