A lighting plan decides, in order, what each room has to do, how many separate layers of light will do it, how those layers group into zones, how many circuits that takes, which dimming technology the fixtures demand, and where on the wall the controls go. Only then does anyone choose a finish. By that point the plan has fixed how many devices sit in the box, and the finish cannot change it.
In short
- Illuminance targets are set by task, not by room. A kitchen has at least two of them, which is why a kitchen almost never has one switch.
- Federal design guidance tells specifiers to set lighting goals as early as possible, then build layers, then divide the space into fine-grained control zones. Hardware is the consequence, not the starting point.
- The Department of Defense lighting criteria go further: when wallbox dimmers are used, there is one for each luminaire type in the room. That sentence decides your gang count.
- Dimming families are not interchangeable. Electronic low-voltage loads need reverse phase, magnetic low-voltage loads need forward phase, and 0-10V is a separate low-voltage signal that does not by itself switch the light off.
Nobody publishes this sequence, so here is ours and where it comes from
We went looking for an institution that publishes the order of lighting decisions from intent to finish, and there is not one. The sequence below is our synthesis of three public sources plus what we see in customer plans, and we would rather say so than dress it up as somebody's standard.
The sources agree on direction of travel. The General Services Administration, in its guidance on saving energy through lighting and daylighting strategies, tells teams to set goals as early as possible in project planning and craft a lighting strategy to achieve them, calls layers of light the best proven strategy, then says to divide the space into fine-grained electric lighting zones. Goals, layers, zones. The DALI Alliance's guide for lighting designers opens the same way, saying the initial step is to pinpoint the client's objectives, the space's purpose and the ambience they aspire to achieve.
| Decision | What it settles | What it forecloses |
|---|---|---|
| 1. Task and target level | How much light each activity needs, per surface | Whether one fixture can serve the room |
| 2. Layers | Ambient, task and accent as separate systems | The minimum number of controlled groups |
| 3. Zones | Which layers are commanded together | The number of switch legs leaving the box |
| 4. Circuits and load | How much wattage sits on each leg | Which control models are rated for it |
| 5. Dimming technology | Forward phase, reverse phase, 0-10V or none | Most of the catalog, immediately |
| 6. Neutral and box depth | What the wall can physically accept | Electronic controls in old boxes |
| 7. Control location and height | Which wall, which side of the door, how high | Where the opening gets cut |
| 8. Device count per box | The gang count | Every plate that does not come in that size |
Light levels are set by the task, not by the room
The first decision is not how bright a kitchen should be. It is how bright a countertop should be while someone is using a knife on it, a much higher number than the one that makes the same room pleasant to walk through. A residential illuminance table published by Penn State's energy conservation course, which the university attributes to the Illuminating Engineering Society, states that how much light is needed depends on the tasks being performed, then gives two separate figures for the same kitchen.
| Space | General level | Task level | What that implies |
|---|---|---|---|
| Kitchen | 30 to 40 footcandles | 50 to 100 at range and sink | Two layers, two controlled groups |
| Living room, bedroom | 10 to 20 footcandles | 20 to 50 for reading | Ambient plus a dimmed reading layer |
| Bathroom | 20 to 50 footcandles | Mirror lighting is its own problem | Separate vanity and ceiling control |
| Hallway, entry | 5 to 20 footcandles | None | The one room that genuinely needs one switch |
Penn State attributes the table to the IES without citing an edition, and the IES recommendations are a paid library, so treat these as a teaching reference rather than the standard. The ratio is what matters: a task surface wants roughly two to three times the general level around it. Two numbers in one room is two layers, two layers is two groups, two groups is two positions in the wall. The Department of Defense criteria make the same separation from the other end, specifying a passageway at no less than a fifth of the nearby task illuminance rather than as an absolute.
Layers are decided before zones, and zones before hardware
A layer is a job: wash the ceiling, light the counter, graze the stone, pick out the painting. A zone is a group of layers commanded together. Conflating the two is the commonest fault in plans that arrive with an order.
The Unified Facilities Criteria for interior and exterior lighting systems, which governs lighting design for US military construction, sets a threshold: areas of control are divided into separate zones for larger spaces, typically above 250 square feet, and separate, independent control is provided for each zone. Your living room is not a barracks, but the logic transfers. Zoning is also where the plan stops being about light and becomes about copper: every zone commanded independently is a separate switch leg back to a box, and you cannot add one later without opening a wall, which is the whole argument of who pays when a wall is closed before inspection.
The sentence that decides your gang count
Most people arrive at a gang count by counting things they want to switch and hoping. There is a published rule, from the same federal criteria.
The UFC states that if wallbox dimmers are used instead of scene wallstations, wallbox dimmers are provided for each luminaire type in the room. Not for each fixture and not for each room: for each type. A dining room with a pendant, a cove and a picture light is three luminaire types, three dimmers and a three-gang box. A bedroom with a ceiling fixture and two matching sconces on one leg is two types and two gangs.
It converts an intention into a quantity with no judgment required. Count the types and you know whether you are shopping in three and four gang territory; the physical consequences are in how to plan a multi-gang switch bank. The same criteria fix where the control goes: manual control devices are located at all room entries, and on the latch side of doors rather than the hinge side where space permits. A switch behind a swinging door is a plan error, not a taste error.
The dimming technology is chosen before any device
This decision eliminates most of the catalog in one move, and it belongs to the fixtures rather than the switch. Choose the switch first and you will be returning it.
| Family | Typical loads | How it controls | The trap |
|---|---|---|---|
| Forward phase (TRIAC, leading edge) | Incandescent, many LED drivers, magnetic low voltage | Cuts the leading edge of each half cycle | Flicker at low load; one dimmer per circuit |
| Reverse phase (ELV, trailing edge) | Electronic low voltage, many modern LED drivers | Cuts the trailing edge | Not interchangeable with forward phase |
| 0-10V | Commercial and architectural LED drivers | A separate low-voltage control pair | Does not switch the load by itself |
| Low-voltage PWM | 12V and 24V LED tape | Pulses the DC supply | Sits downstream of a driver, not on 120V |
| Digital bus (DALI) | Commercial installations | Addressable two-wire bus carrying data and bus power | Rarely proportionate in a house |
Leviton publishes an application note stating the incompatibility in both directions: magnetic low-voltage loads can only be controlled by forward phase dimmers, because of kickback voltage that can damage the dimmer or the load, while electronic low-voltage loads generally require reverse phase control and are not suitable for forward phase dimming. A damage risk one way, a non-function the other.
Our own rotary dimmers are forward phase TRIAC devices and the consequences are published rather than buried. Only one belongs on any given circuit: on a three-way or four-way arrangement the dimmer takes one position and a mechanical toggle takes the other, which is how the dimmer range is meant to be specified alongside the toggle range. Trailing-edge and ELV fixtures do not belong on them at all, and a ceiling fan motor never belongs on a light dimmer under any circumstance, which is what the fan speed control switch exists for. The full picture is in how rotary dimmers work and what they dim.
0-10V: the signal does not turn the light off
Architectural LED drivers very often want 0-10V, and it behaves unlike anything else on that list. A Department of Energy study of 0-10V control for LED luminaires describes it precisely: analog 0-10V control requires two low-voltage wires between the control and the driver, and as a result line voltage to the driver is typically switched in installations to ensure the ability to create an off state.
Read that twice if you are planning a wall. The dial is a signal, not a switch. To turn the fixture off you need either a relay or power pack switching the line voltage, or a control model specifically rated to switch its own load, which is a question to settle in writing with the driver and control manufacturers before the box is sized. In practice a 0-10V zone frequently needs two positions in the wall where a TRIAC zone needs one. Our 0-10V rotary controller and the 12-24V PWM knob are low-voltage devices and neither belongs on a TRIAC circuit. The background is in 0-10V and PWM low voltage dimmers explained.
The neutral in the box decides what you may install
Electronic controls draw a small standby current, and that current has to go somewhere. The code answer arrived some years ago and governs what you can put in an old wall.
Writing in IAEI Magazine, L. Keith Lofland, a former director of technical services and of codes and standards at the International Association of Electrical Inspectors, explains that the grounded conductor is required at all switch locations where switches control lighting loads, and gives the reason: many electronic lighting control devices require a standby neutral current to maintain a ready state of detection. Using the equipment grounding conductor as the return path instead introduces circulating current onto that system.
He also sets out a numeric ceiling new to most readers. Where an exception permits electronic lighting control switches to use the equipment grounding conductor, the number of such switches on a branch circuit is limited to five, and the number on any feeder on the load side of a system or main bonding jumper to twenty-five. Those limits cover that category of device rather than every dimmer ever made, but an inspector can count. The reading for a renovation is simple: a 1920s box with two cloth-covered conductors and no neutral will take a mechanical toggle and will not take most electronic controls, which is cheaper to discover before the finish chart comes out. The method is in how to tell which wire is which in an old wall box and what your walls allow.
Load, heat and why a bank of dimmers is not a bank of switches
A dimmer dissipates heat and the metal front of the device is part of how it sheds it. Gang several together and the side heat sink sections have to come out, after which the maximum load is reduced. Manufacturers publish that reduction as a derating table in the instruction sheet.
The derating is per model, and some models need none at all: at least one manufacturer's instruction sheet states that a particular wattage requires no derating in multi-gang applications. So you cannot know how many dimming positions fit in a box until the load on each is fixed. A bank of mechanical toggles has no such constraint, which is one real argument for splitting a long run. Box volume is the other half: each yoke counts against the fill calculation, and a deep device in a shallow old box wants a bigger box, not force. The numbers are in electrical box types and sizes and the circuit arithmetic in how many outlets can be on one circuit.
Where the control goes, and how high
Height is the decision people assume is standardized and is not. No national rule sets a mounting height for a light switch in a house. What exists are reach ranges, from accessibility guidance rather than the electrical code.
The Department of Housing and Urban Development's training material on controls in accessible locations gives figures that are useful even where they are not binding. Controls and outlets should range from 15 to 48 inches above the floor. Over an obstruction between 20 and 25 inches deep the maximum mounting height must be reduced to 44 inches, and beyond 25 inches the location is considered outside the reach range. For a side reach over a cabinet the maximum is 46 inches, with the obstruction no more than 36 inches high, and near an inside corner the manual prescribes at least 36 inches from the corner.
Two honest qualifications. These requirements apply to covered multifamily dwellings, not to a single-family house, so in a private home they are best practice rather than law. And the electrical code's own height provision is a ceiling of about six feet seven inches to the center of an operating handle, far above any comfortable height, so it settles nothing a designer cares about: the code tells you how high is too high, not how high is right. The useful rule remains the UFC's, at every entry on the latch side, after which the height mostly answers itself against the counter, the backsplash or the dado the switch has to live with.
What the code requires, and what it leaves to you
State adoptions carry the baseline in plain language. Wisconsin's administrative code, for instance, provides that at least one wall switch-controlled lighting outlet shall be installed in every habitable room, kitchen and bathroom. We have not read the national code's own text, which is published only behind a reader application, so we cite the state adoptions and the professional literature rather than pretending to quote the source. Section numbering varies by jurisdiction, and the adopted text is what your inspector enforces.
Energy codes are where the real control requirements live, and they are regional. California's Title 24 residential measures are the strictest commonly encountered set: dimmers required in habitable rooms; vacancy sensors with automatic shutoff on at least one luminaire in bathrooms, laundry rooms, utility rooms, walk-in closets and garages; undercabinet and display lighting switched separately from the ceiling lighting in the same room; lighting controlled separately from ceiling fan functions; and blank electrical boxes above five feet from the floor capped at the number of bedrooms. Those are circuit and box decisions written into law, taken long before any finish chart, and they are Californian rather than national.
One correction we owe our readers. The energy standard most often cited in this context, ASHRAE/IES 90.1, carries its scope in its own title: it covers sites and buildings except low-rise residential buildings. If you are specifying a house of three storeys or fewer, 90.1 is not your document, whatever a blog tells you. Your documents are the adopted electrical code, your state energy code, and the manufacturer's instruction sheet.
Safety, and where this stops being a planning exercise
Everything above is design. The moment anybody opens a wall, different rules apply.
Turn the breaker off at the panel before touching a device, then verify the absence of voltage at the box with a tester you have just proved on a circuit you know to be live. Work de-energized; testing on live circuits is work for qualified persons only. If the work involves new circuits, a service change, or anything your jurisdiction defines as more than a like-for-like device replacement, a permit and a licensed electrician are required, and whether a task crosses that line is decided by your local code and by the authority having jurisdiction, not by us and not by a manufacturer. When in doubt, ask the inspector before the drywall, which is the argument of do you need a permit and a licensed electrician and what a rough-in inspection actually covers.
We also will not confirm a wiring or dimming compatibility without written confirmation from the fixture or driver manufacturer, which our installation and compatibility page sets out in detail.
What is still open when the finish is finally chosen
By the time the finish chart comes out, the plan has fixed the gang count, the device type in every position, the location of every opening and the technology behind it. What remains is a narrower choice than most people expect.
Our switches are single-piece solid brass units, plate and mechanism made as one, so a plate sold on its own will not fit over one of ours. Two screws per gang, a one-gang taking two and a four-gang eight. Eight finishes on the knurled toggle range and seven on the plates, three of them hand-brushed. Unlacquered is made to order, takes about three weeks of production and is not returnable, because it is a living finish meant to change.
Send a plan before ordering. What we need is the gang count per box, the device type in each position, the dimming technology where there is any, and whether a neutral is present; what we do not need yet is a finish. Use design your wall for a single bank and send your plan for anything bigger; designers specifying repeatedly belong on the trade program. Samples come last, from the sample set, on the actual wall under the actual lamps the plan specified, with the finishes page for after that rather than before.
Frequently asked questions
What is a lighting plan?
A drawing and a schedule stating what each space has to do, which fixtures do it, how they group into controlled zones, which circuits serve them, and where the controls sit. It is a document about light and copper, not a shopping list of fittings.
What does a lighting designer decide first?
The intent and the target levels. Federal design guidance tells teams to set lighting goals as early as possible in project planning and then build a strategy to achieve them, which is the opposite of starting from a product you liked.
How many light switches should a room have?
As many as it has luminaire types to control independently. The Department of Defense lighting criteria say wallbox dimmers are provided for each luminaire type in the room, which converts the design decision into a gang count directly.
Do I need a neutral wire at the switch?
For most electronic controls, yes, and modern adopted code requires a grounded conductor at switch locations controlling lighting loads. Older houses frequently lack one, and that single fact rules out large parts of the catalog until the wiring changes.
Can I put two dimmers on a three-way circuit?
No. One dimmer per multi-location circuit, with a mechanical switch in the other position, unless the manufacturer's own instruction sheet publishes a companion arrangement for those exact models. Those ceilings are per product and never generalize.
What does 0-10V dimming need that TRIAC does not?
A separate low-voltage control pair to the driver, and a way to actually switch the load off, since the signal does not do it. That is either a relay or power pack, or a control model rated to switch its own load, confirmed in writing before the box is sized.
How high should a light switch be?
There is no national requirement. Accessibility guidance for covered multifamily housing puts controls between 15 and 48 inches above the floor, lower over deep obstructions, and the electrical code only sets a ceiling of roughly six feet seven inches to an operating handle. In a private house it is a judgment made against counters, dados and door swings.
Does the code require a dimmer anywhere?
Not the electrical code. California's residential energy measures do require dimming in habitable rooms and vacancy sensors in several others. Energy requirements vary by state, so check the one your jurisdiction has adopted.
When does the finish get chosen?
Last, and from a physical sample on the wall the plan just specified. Anything decided about appearance before the gang count is a guess the plan is free to overrule.
The short version
A lighting plan is a sequence of constraints, and the finish sits at the end where it can do no harm. Count the tasks, then the layers, then the zones, then the circuits, settle the dimming technology, open a box and look for a neutral, then cut the openings at the entries on the latch side. The gang count falls out of that work, and only then does a switch and outlet range or a wall plate become a real choice. A single hallway switch needs none of this; a room with more than one thing to light needs all of it, and so does any wall currently open. Both ends of the budget are in where the first $500 of brass goes and specifying for year five. Send us the plan and we will tell you what fits it.
Last updated: November 9, 2026
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