Quick answer: Choose an LED wall washer to illuminate a large wall evenly; choose grazing when you want to emphasize its texture. According to Wikipedia's wallwasher overview, wallwashing uses asymmetric fixtures to create even illumination across the surface.
Start with the effect you want on the wall, then compare the optics and layout that can deliver it. This guide separates washing from grazing, shows what a beam-angle calculation can tell you, and gives a selection checklist for indoor walls and outdoor facades. For other lighting calculations, use the LEDask calculator hub.
Wall washing or grazing: which effect do you want?
Choose washing for a uniform background and grazing for visible surface texture. Grazing places the luminaire directly in front of the wall to emphasize the material; ERCO also explains that special optics are needed to avoid a hot spot immediately above the fixture. See ERCO's wallwashing guide.
| Your intended result | Approach to compare | What to assess in a sample layout |
|---|---|---|
| A wall that reads as an evenly lit surface | Wall washing | Evenness across its width and height |
| Stone texture as the main visual feature | Wall grazing | How clearly the surface relief appears |
| Light starting near the ceiling | Wallwasher optics | Whether the upper wall remains unlit |
| A textured wall without a bright patch above the light | Grazing optics | Whether the near-fixture hot spot is controlled |
The table applies ERCO's distinctions between washing, grazing and optical quality; according to ERCO, good wallwasher optics start the light directly below the ceiling and maintain horizontal and vertical uniformity, even with larger fixture spacing.
For a stone wall, decide whether the priority is the wall as a continuous surface or the texture of individual stones. That decision gives you a useful comparison criterion before you start comparing fixture sizes or power ratings.
Choose optics for the surface you need to light
An asymmetric distribution is central to wallwashing. According to Wikipedia's architectural lighting definitions, a wallwasher is an asymmetric fixture designed to illuminate a wall flatly from ceiling to floor. A product's wattage alone does not describe that distribution.
LEDs allow optical control: the US Department of Energy identifies their small size and bright output as features that enable it. When comparing products, make the wall-lighting pattern part of the comparison alongside light output and electrical power.
For a corridor, consider whether you need light on both opposing walls. According to ERCO, a double wallwasher illuminates opposite corridor walls from one luminaire. That is a specific optical arrangement to look for, rather than an assumption to make about every wallwasher.
Estimate coverage with beam angle
Use beam angle to estimate spread, then assess uniformity separately. According to Wikipedia's beam-angle definition, IES measures the angle between directions where intensity reaches 50% of the maximum. That boundary is an intensity reference, not a promise of equal brightness throughout the beam.
The beam angle calculator uses this geometry:
Beam diameter = 2 × distance × tan(beam angle ÷ 2)
For the examples below, the assumed beam is circular, its axis meets the target surface at a right angle, and distance is measured along that axis. A real asymmetric wallwasher does not produce this circular pattern, so the calculation is a first approximation for comparing spread, not a wallwasher spacing prescription.
Worked example: assumed wide beam
Assumed inputs: a 90° circular beam and a target surface 1 m away.
- Half-angle = 90° ÷ 2 = 45°.
- tan(45°) = 1.
- Diameter = 2 × 1 m × 1 = 2 m.
This means the geometric beam diameter is 2 m under those assumptions. It does not establish an evenly illuminated wall width or a suitable gap between fixtures.
Worked example: assumed narrower beam
Assumed inputs: a 36° circular beam and the same 1 m distance.
- Half-angle = 36° ÷ 2 = 18°.
- tan(18°) ≈ 0.32492.
- Diameter ≈ 2 × 1 m × 0.32492 = 0.64984 m, rounded to 0.65 m.
At the same assumed distance, the narrower beam covers less width. Neither calculation includes a brightness target, so neither tells you how much light the wall receives or how many fixtures meet your intended illumination level.
Plan a row without inventing a spacing rule
There is no universal wallwasher spacing distance in the sources used here. According to Wikipedia's wallwasher overview, three or more asymmetric fixtures in a line can produce evenly illuminated walls. Treat that as a possible arrangement, not a minimum fixture count for every wall.
For a proposed layout, use this sequence:
- Define whether you want an even surface or emphasized texture.
- Establish the wall dimensions and the mounting positions available.
- Compare the manufacturer's wall-lighting distribution for those positions.
- Assess the upper edge, lower edge and joins between adjacent beams together.
The reason to assess both directions is concrete: according to ERCO, good wallwasher optics achieve both horizontal and vertical uniformity. A layout that looks even across the middle of the wall has not yet demonstrated that result over the full surface.
Select indoor and outdoor fixtures for their setting
Wallwashing can serve both indoor walls and outdoor facades. According to ERCO, uniform wallwashing suits gallery and museum artwork, while illuminated exterior facades can frame outdoor spaces.
For outdoor selection, distinguish the dust code from a complete assessment of exposure. According to Wikipedia's IP-code reference, IEC 60529 defines the IP classification, and the first digit 6 means dust-tight. The IP6X notation identifies that dust protection; it does not supply a water-protection requirement for your project.
Use this buying checklist:
- Optical purpose: washing, grazing or an opposing-wall corridor arrangement.
- Coverage: the proposed distribution over the actual wall dimensions.
- Appearance: the colour temperature you want; kelvin describes that colour characteristic, not light output.
- Location: a fixture rating suited to the intended indoor or outdoor exposure.
- Electrical arrangement: the specified supply and driver requirements.
Use a qualified electrician for mains-voltage connections. This is a fixture-selection checklist, not a mains-wiring procedure.
FAQ
What is an LED wall washer?
It is a fixture intended to light a large vertical surface evenly. According to Wikipedia's architectural lighting definitions, wallwashers use asymmetric distribution to illuminate the wall from ceiling to floor.
Should I wash or graze a stone wall?
Choose according to the effect you want. ERCO distinguishes uniform wallwashing from grazing positioned directly in front of the wall to emphasize texture.
How close should a wall washer be to the wall?
The sources here do not establish a universal distance. ERCO describes grazing as directly in front of the wall, while its wallwashing guidance emphasizes optical distribution and uniformity.
Does beam diameter tell me the correct fixture spacing?
No. The assumed 90° circular beam at 1 m gives a 2 m diameter through 2 × 1 × tan(45°) = 2; that geometry does not calculate the combined illumination of adjacent asymmetric fixtures.
Can I use wall washers outdoors?
Yes; according to ERCO, wallwashing also applies to exterior facades. Select a fixture whose location rating suits the exposure rather than assuming that a wallwasher designation establishes outdoor suitability.
Jack Shi
Founder & editor, LEDaskJack Shi builds and writes LEDask, an independent LED-lighting tools project operated by clooms. He designs the calculators, checks their formulas and reference values against published engineering data, and writes the guides across the site.
