Illuminating a wall can be done in one of two ways: wallwashing or wall grazing. The distinction between these two core lighting details is the fixture’s distance from the wall surface. In a wallwash detail, the luminaire is typically a minimum of 12 inches away from the wall plane, allowing for an even application of light that gives the wall texture a flat appearance. In a wall grazing detail, the fixture is positioned very close to the wall (no further away than 12 inches) in order to highlight and bring out the wall texture. The overall height of the wall informs the luminaire’s distance from the wall. 

Things to consider for wall lighting:
1. The human eye has an easier time deciphering vertical surfaces than horizontal surfaces.
2. Illuminated vertical surfaces are most successful as an indirect lighting solution when the surface has a light-colored, matte finish.
3. Dark colors and specular surfaces, such as polished stone, are difficult to illuminate.
4. Illuminated walls can be a source of glare.

J.E. Flynn and S.M. Mills, Architectural Lighting Graphics, Van Nostrand Reinhold, New York, 1962, p. 182–183
M. David Egan and Victor Olgyay, Architectural Lighting, Second Edition, McGraw Hill, p. 226–227

Mark Karlen and James Benya, Lighting Design Basics, John Wiley & Sons, 2004, p. 59