Choosing beam angles

The short answer

Use a narrow beam close to the wall to graze it and bring out texture, and a wider beam further away to wash it with even light. The taller the surface you need to reach, the narrower the beam (and the more output) you need. Beams should overlap enough that you don’t see dark gaps between luminaires.

What a beam angle means

A luminaire’s beam angle is normally the angle within which the light stays at or above half of its peak intensity. Light continues outside that angle, fading off; the wider field angle is usually measured to one tenth of peak. So two luminaires with the same beam angle can still look different on a wall, which is why we check designs with photometric files rather than beam angles alone.

The main beam types

Beam	Approximate angle	Typical use
Spot / very narrow	Under about 10°	Picking out a single feature, a tall column or a spire from a distance
Narrow	About 10–20°	Grazing tall walls, lighting columns and piers
Medium	About 20–40°	Grazing or washing walls of moderate height
Wide	About 40–60°	Washing lower walls, canopies and soffits
Flood	Over about 60°	Even light over broad, low areas
Oval / elliptical	For example 10° × 60°	Spreading light along a wall while keeping it tight in the other direction, or lighting a tall, slim feature
Asymmetric	Varies	Throwing light up or across a wall from a luminaire set close to it, with little light going outwards

Names vary between manufacturers, so always check the angle given on the datasheet.

Grazing versus washing

Grazing puts the light source very close to the surface, typically within a few hundred millimetres, and aims it almost parallel to the wall. Light hits the surface at a steep angle, so every bump, joint and texture casts a shadow. It suits stone, brick, timber cladding and textured render. It’s unforgiving on uneven or patched surfaces, because it shows every flaw.

Washing sets the luminaire further back and aims more directly at the surface. The light is flatter and more even, texture is softened, and colour reads more clearly. It suits smooth render, painted surfaces, and colour-change schemes where even colour matters.

Many schemes use both: grazing on textured features, washing on plain areas.

Height and beam

The narrower the beam, the more its light is concentrated, so it reaches further up a wall before it fades. A wider beam spreads the same light over a larger area and runs out of strength sooner.

The table below gives an indicative height a beam can usefully light when grazing or washing up a wall from the base. It is a rough guide only: real reach depends heavily on the luminaire’s output, the surface colour and reflectance, how bright the surroundings are and the effect you want. We confirm reach for real products with a calculation.

Beam	Indicative reach up a wall
Spot / very narrow	12 m and above, with high-output luminaires
Narrow	About 8–15 m
Medium	About 4–8 m
Wide	About 2–5 m
Flood	Up to about 3 m

How wide a beam spreads

For floodlights aimed at a facade from a distance, the beam’s width on the wall follows simple geometry: width ≈ 2 × distance × tan(beam angle ÷ 2). At 10 m from the wall:

Beam angle	Approximate width at 10 m
10°	1.7 m
20°	3.5 m
30°	5.4 m
45°	8.3 m
60°	11.5 m

This is the width to the half-intensity edge. The light continues beyond it, more dimly.

Spacing and overlap

• Overlap the half-intensity edges. As a starting point, space luminaires so that the edge of one beam meets the edge of the next at the height where you want the light to look even. Closer spacing gives a more even result; wider spacing gives a deliberate scalloped rhythm.
• Narrow beams need closer spacing at the base of the wall, because they take longer to spread out. With narrow grazers, the bottom of the wall often shows distinct pools of light before the beams merge higher up.
• Continuous linear luminaires avoid scallops altogether and give the most even grazing.
• Match spacing to the architecture. One luminaire per pier, bay or window is often better than an even spacing that ignores the building’s rhythm.

Controlling spill

A tighter beam keeps more light on the building and less in the sky or in neighbours’ windows. Accessories such as snoots, louvres, glare shields and spread lenses can trim or reshape a beam where the product offers them. Aim beams to stop short of the roofline when lighting upwards, so that light isn’t thrown into the sky. See planning a facade lighting scheme for obtrusive light guidance.

How we can help

Send us elevations and photos and we’ll suggest beams and positions, then check them with photometric files in a lighting calculation. Start a project.