The outermost layer of the objects and materials in a space.

Surface is the final layer of a project, and like many other principles of interior design, it has resonance with the aural, visual, and tactile qualities of a design.

Surfaces are the main experience of an interior—paint on walls, flooring, laminates on cabinetry, fabrics on furnishings. Surfaces are closely aligned with acoustics; they have reflective and absorptive qualities that add to the aural perception of a project. Color, whether integral to material or applied, also reflects or absorbs the light in a room. Texture—subtle surface deformations, stitching in fabric, or the smooth finish of a plaster wall—allows for the touch and feel of objects and surfaces.

There are essentially two types of surfaces in the physical world diffuse and metallic. Diffuse materials have a roughness to them that sends light rays scattering in all directions, which makes an object appear to have varying levels of roughness. This effect, known as the “Fresnel effect,” states that the amount of light reflected from a surface depends on the viewing angle at which it is perceived. Metallic surfaces are defined by their periodic table of elements—gold, silver, copper, aluminum, or iron. They are good conductors of heat and electricity. In addition, metallic surfaces have absorptive, specular, and refractive qualities that should be taken into consideration.

Of all the tools that interior designers use to define space, surfaces are perhaps the simplest and, at the same time, most complex. The impact of the detailed, behind-the-scenes work that allows an interior to function effectively will be lost unless the finished surfaces are well integrated into the project.