Cove Lighting Design: How to Hide the Source and Get the Detail Right
Cove Lighting Design: How to Hide the Source and Get the Detail Right
Cove lighting is the only lighting technique judged entirely by what you cannot see.
A downlight is a visible object. A pendant is chosen to be looked at. A cove is different: it succeeds when the room glows and nobody can locate the source, and it fails the instant someone can see the strip, count the diodes, or spot a bright band where there should be an even wash.
That makes it unusually unforgiving. Most lighting mistakes are a matter of degree. A cove mistake is binary. Either the source is hidden or it is not, and the difference between the two is often twenty or thirty millimetres in a plasterboard detail drawn months before anyone orders a light fitting.
It is also the technique that most closely matches what architects usually want from lighting. The ambition is for the light to serve the building rather than compete with it: to reveal a surface, a material or a form while remaining anonymous itself. A cove, done well, is the purest version of that idea. This guide is about how to draw that detail so it works.
Why the Published Dimensions Contradict Each Other
Search for cove dimensions and you will find numbers that do not agree. One source says 150mm minimum. Another says 60 to 80mm. A third says 100 to 300mm. A fourth says 75 to 100mm is the sweet spot.
They are not contradicting each other. They are measuring different things, and almost none of them say which.
A cove detail has at least three separate dimensions, and "depth" is used loosely for all of them:
| Dimension | What it means | What it controls |
|---|---|---|
| Setback below the ceiling | Vertical distance from the ceiling plane down to the top of the cove | How far the light travels before it hits the ceiling, and therefore how evenly it spreads |
| Pocket depth | The clear internal depth of the channel the strip sits in | Whether the strip is concealed from normal viewing angles |
| Strip setback from the lip | Horizontal distance from the strip to the front edge that hides it | Whether anyone standing in the room can see the source |
Once those are separated, the published figures stop conflicting. A source saying "minimum 150mm" is usually talking about setback below the ceiling. A source saying "60 to 80mm" is talking about clear pocket depth. Both can be right.
Working figures to start from, drawn from published guidance rather than from any standard:
- Setback below the ceiling: around 150 to 220mm on a typical residential ceiling. More setback gives a more even ceiling wash.
- Clear pocket depth: 60 to 80mm minimum, deeper for higher output strips.
- Strip setback from the lip: roughly 30 to 45mm.
One detail that catches people out. Clear pocket depth means clear with the aluminium profile installed. A 15mm profile in a 70mm pocket leaves 55mm, which may put you under your intended dimension without anyone noticing until the strip is in and visible.
The Classical Principles
The following principles come from established lighting design literature, published by Architectural Lighting and drawn from textbooks including Flynn and Mills' Architectural Lighting Graphics, Egan and Olgyay's Architectural Lighting, and Karlen and Benya's Lighting Design Basics. They predate LED and they still hold, because they describe geometry and reflection rather than technology.
1. Joints and gaps show up in the light. Any break between fixtures appears as a dark spot on the ceiling. Where individual fixtures are used rather than continuous strip, place them end to end, staggered or slanted, to eliminate the shadow at each end.
2. The top of the source should be level with the cove fascia. If it sits below, the fascia casts a shadow line across the ceiling wash.
3. Stop the cove short of the end wall. Running it hard into the corner produces a sharp cutoff line. Stopping short lets the light fade.
4. Finish matters more than people expect. The ceiling being washed should be a high-reflectance matte or satin surface. The inside of the cove itself should be flat white. Both minimise specular reflection, which is what turns an even wash into visible bright patches.
5. Keep clear of inside corners. As a cove approaches an end wall, maintain a minimum clearance of around 305mm (12 inches) at inside corners to prevent hotspots, where light from two directions compounds.
6. More setback gives more uniformity. As the cove's distance from the ceiling plane increases, the evenness of the ceiling brightness increases with it. This is the single most useful relationship in cove design: if the wash is patchy, the answer is usually more setback rather than a different strip.
A related positioning note from published guidance: keep the source roughly 50 to 150mm (2 to 6 inches) away from any reflective surface inside the cove to minimise shadows and reflections.
Choosing the Strip
Detailing determines whether the source is hidden. Strip selection determines whether the light itself looks expensive or cheap.
Dots or no dots
Conventional LED strip places individual diodes at intervals along a flexible board. Densities vary widely by product, commonly from around 60 up to 320 or more LEDs per metre, and the lower the density the more visible the individual points of light. In a deep cove viewed from across a room, a high density strip is usually fine. In a shallow cove, on a short throw, or anywhere the strip is visible at close range, you see the dots, and the whole ceiling reads as cheap.
COB strip uses a continuous phosphor-coated emitting surface rather than discrete diodes, so it has no visible dots at all. Where the cove is shallow, the throw is short, or the finish standard is high, it is worth the cost difference.
Colour rendering
The same rule that applies everywhere else applies here, and it applies more visibly, because a cove washes large areas of ceiling and wall.
Specify Ra 90 minimum, and Ra 95 with R9 above 50 where finishes matter. An Ra 80 strip washing a timber ceiling makes the timber look flat, and washing a room full of people makes skin look slightly grey. Nobody names the problem. Everybody feels it.
Aluminium profile
Use one, even though the strip is hidden. It does two things: it keeps the line dead straight, which matters over a long run, and it takes heat away from the diodes, which is a major factor in whether the cove still looks the same in year five.
Voltage drop
On a long run, a single power feed produces a visibly dimmer far end. Maximum run length before this becomes noticeable depends on the strip's operating voltage, its current draw per metre and its conductor size, so it must be confirmed against the specific product. As a rough planning figure, runs beyond around 5 to 6 metres commonly need feeding from both ends or splitting into separately fed segments, and 12V strips reach their limit sooner than 24V ones. This is a wiring decision made at design stage, not something that can be fixed later without opening the ceiling.
Dimming
Cove lighting dims well and benefits from it. Specify a control protocol at the outset, commonly 0 to 10V or DALI, and confirm driver compatibility with the chosen dimmer before ordering.
Two Different Jobs: Ceiling Wash and Wall Wash
A cove can light the ceiling or light the wall, and the detail is not the same for both.
Ceiling wash is the classic application. The strip fires upward, the ceiling becomes a large soft reflector, and the room fills with diffuse light that appears to come from nowhere. This wants generous setback below the ceiling and a high-reflectance matte ceiling finish.
Wall wash fires down or outward, grazing the wall below. This reveals texture, which is wonderful on stone, plaster or timber, and unforgiving on anything with a flaw in it. The closer the source sits to the wall, the more the texture is exaggerated.
Two detail variations worth knowing, both from professional lighting practice:
Removing the upstand that conceals the lamp creates a shelf detail. More light escapes the cove, which is good for wall washing, but viewing angles into the cove must then be checked carefully, particularly at corners where someone may see along the length of it.
Chamfering the cove creates a light edge that becomes illuminated by reflected light. This works well for ceiling slots. It is less effective for wall washing, because the chamfer moves the source further from the wall.
The Coordination Problems Nobody Warns You About
This is where cove lighting actually fails on site, and none of it is about the light fitting.
The ceiling support grid. Metal furring channels supporting the ceiling can sit inside the cove and produce a repeating pattern of hotspots and shadows across the wash. The fix is to specify an internal skin of plywood or plasterboard lining the cove, so the light sees a continuous flat surface rather than a structural grid.
HVAC in the same void. Cove details are sometimes used to conceal return air, which can work provided the opening does not lose too much light. Supply air discharging into a cove is a different matter. Older guidance warned that air dumping onto the light source over-cools it and reduces output, which was true of fluorescent lamps, since they have an optimum operating temperature and lose output when run too cold. LEDs behave the opposite way: cooler junction temperatures improve both output and life. The modern objections are different but still real. Moving air carries dust, which settles on the strip and diffuser and dims the cove over time, and a cove used as an air path is far harder to clean than one that is not. Condensation is a further risk where warm supply air meets cold surfaces. If the mechanical drawings put a supply diffuser in the cove, raise it early.
Maintenance access. A cove detailed with no way to reach the strip is a cove that gets ripped out when the driver fails. Confirm how the strip and driver will be accessed, and where the driver actually sits, before the detail is signed off.
Driver location. Drivers need to be somewhere accessible, somewhere ventilated, and somewhere their noise will not be noticed. That is a coordination item, not an afterthought.
Sequence and trades. The cove is built by the ceiling contractor, the strip is installed by the electrician, and the finish is applied by the plasterer and decorator. All three affect whether the light works. A dimension agreed in a drawing survives only if it survives all three.
Detailing Checklist
Dimensions
- Setback below ceiling specified, typically 150 to 220mm as a starting point
- Clear pocket depth specified, measured with the aluminium profile in place
- Strip setback from the concealing lip specified, roughly 30 to 45mm
- Sightlines checked from the furthest and lowest likely viewing position
- Corner clearance of around 305mm maintained at inside corners
- Cove stopped short of end walls to avoid a hard cutoff
Strip and electrical
- COB versus standard strip decided based on cove depth and viewing distance
- Ra 90 minimum, Ra 95 with R9 above 50 where finishes matter
- Aluminium profile specified for straightness and heat dissipation
- Feed strategy resolved for long runs, confirmed against the actual strip voltage and current draw
- Dimming protocol specified and driver compatibility confirmed
- Driver locations identified: accessible, ventilated, acoustically sensible
Finishes
- Ceiling being washed is high-reflectance matte or satin
- Inside of the cove is flat white
- Wall being grazed is good enough to survive raking light
Coordination
- Ceiling support channels lined so they do not cast a pattern
- No supply air discharging into the cove (dust deposition and condensation risk)
- Maintenance access confirmed for strip and driver
- Detail issued to ceiling contractor, electrician and plasterer, not just one of them
Six Ways Coves Fail
1. You can see the strip. The single most common failure, and almost always a dimensional problem: not enough pocket depth, not enough setback from the lip, or a profile that ate the clearance.
2. You can see the dots. Conventional discrete-diode strip in a shallow cove or at close viewing range. COB solves it.
3. Hotspots and shadow lines. Usually the ceiling support grid casting a pattern, the source sitting below the fascia, or corners where two runs compound.
4. One end is dimmer than the other. Voltage drop on a long single-fed run. Confirm the limit against the actual strip, and fix it at design stage or live with it.
5. The colour is flat. Ra 80 strip washing a large area. Timber goes lifeless and skin goes grey, and nobody can say why.
6. Nobody can reach it. A beautiful detail with no maintenance access has a lifespan measured by its first driver failure.
Frequently Asked Questions
How deep should a cove be? It depends which dimension is meant, which is why published figures appear to disagree. As working starting points: setback below the ceiling of around 150 to 220mm on a typical residential ceiling, clear pocket depth of 60 to 80mm minimum, and strip setback from the concealing lip of roughly 30 to 45mm. Critically, clear pocket depth must be measured with the aluminium profile installed, since a 15mm profile in a 70mm pocket leaves only 55mm. Deeper coves and greater setback produce a more even wash. These are design practice figures rather than standard requirements.
Why can I see the LED strip in my cove? Almost always a dimensional problem rather than a fitting problem. Either the pocket is too shallow, the strip sits too close to the concealing lip, or the aluminium profile reduced the clear depth below what was drawn. Check sightlines from the lowest and furthest position anyone will realistically stand or sit, since a cove that conceals the source from directly below may still expose it from across the room. Corners are the usual weak point, because people can see along the length of the cove.
What causes hotspots in cove lighting? Three common causes. First, the ceiling support grid inside the cove casting a repeating pattern, which is solved by lining the cove with a continuous plywood or plasterboard skin. Second, the source sitting below the cove fascia rather than level with it, which throws a shadow line. Third, inside corners where light from two directions compounds, which is why a clearance of around 305mm at inside corners is recommended. Specular or glossy surfaces inside the cove or on the ceiling make all three worse.
Should I use COB LED strip in a cove? Use COB where the cove is shallow, the throw is short, or the strip may be visible at close range. Conventional strip places discrete diodes at intervals along the board, and at lower densities those individual points are visible, which makes the whole ceiling read as low quality. COB strip uses a continuous phosphor-coated emitting surface instead of separate diodes, so there are no dots to see at any viewing distance. In a deep cove viewed only from across a room, a high density conventional strip is often perfectly acceptable and cheaper. Either way, specify Ra 90 minimum, and Ra 95 with R9 above 50 where timber, stone or skin tones are being washed.
How long can a cove LED run be before brightness drops? Voltage drop makes the far end of a long single-fed run visibly dimmer. The limit depends on the strip's operating voltage, current draw per metre and conductor size, so it has to be confirmed against the specific product rather than assumed. As a rough planning figure, runs beyond around 5 to 6 metres commonly need feeding from both ends or splitting into separately fed segments, and 12V strips reach that point sooner than 24V ones. It is a design stage decision, because correcting it afterwards means opening the ceiling.
Do I need an aluminium profile if the strip is hidden? Yes, for two reasons that have nothing to do with concealment. A profile keeps the strip dead straight over a long run, and a wandering line is visible in the wash even when the strip is not. More importantly, it conducts heat away from the diodes, which is a major factor in how the output and colour hold up over years of operation. Remember to account for the profile thickness when specifying clear pocket depth.
Can a cove be the only light in a room? For ambient light, yes, and it does that job beautifully. But a cove produces soft, even, directionless light, which means a room lit only by cove lighting has no focus, no sparkle and no task light. Add task lighting where people read or work, and some accent lighting for depth. The cove provides the base layer that everything else sits on.
What colour temperature should cove lighting be? The same as everything else in the same sightline. A cove washing a ceiling is a large visible surface, so any mismatch with nearby downlights or lamps is immediately obvious. In residential and hospitality settings 2,700K to 3,000K is usual. Consistency matters more than the exact figure, and colour consistency between strip reels matters too, so ask about binning tolerance when a run spans multiple reels.
Notice
This article is published by Archlior for general information and educational purposes. It is written for architects, interior designers and specifiers as an introduction to cove and indirect lighting detailing.
It is not professional lighting design advice, engineering advice, or a statement of regulatory compliance for any project.
Dimensions and specifications given here are design practice starting points drawn from published guidance and lighting design literature. They are not standard requirements, and they must be verified against the specific products, ceiling construction, viewing geometry and regulations applicable to your project.
Before proceeding, coordinate the detail with the ceiling contractor, the electrical contractor, the mechanical engineer and a qualified lighting designer.
Archlior accepts no liability for any loss, cost or damage arising from reliance on the information in this article. Readers act on it at their own discretion and remain responsible for compliance with all applicable regulations.
Last reviewed: August 2026.