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The job looks simple from below, but most of it happens above the ceiling. The electrician plans the layout around joists, ducts, pipes and fire blocking, chooses fixtures suited to what is above them, fishes cable between the openings and connects the lights to a circuit and a switch or dimmer that can handle them. Under an attic, the fixtures must also respect the insulation and the air barrier.
This page goes further than general lighting advice: how to plan a layout, how new-construction housings, remodel housings and wafer lights differ, what changes under an insulated ceiling or a garage ceiling, how to avoid flickering dimmers, and what happens to the drywall once the lights are in.
Types of pot lights: new-construction housings, remodel housings and slim LED wafer lights
- New-construction housings: a can on hanger bars fastened between the joists before the drywall goes up, for new builds, gutted rooms and basements with an open ceiling.
- Remodel housings: a can that goes in through a hole cut in finished drywall and clamps to the ceiling from below, for ceilings that stay in place.
- Slim LED wafer lights: an ultra-thin fixture with a small junction box beside it on the cable, needing very little depth, which helps under ducts and in shallow ceiling cavities.
- Adjustable and gimbal trims: fixtures that tilt to aim light at a wall, a fireplace or artwork rather than straight down.
- Damp- and wet-rated models: fixtures marked for bathrooms, soffits and covered porches, where moisture would damage a standard model.
- Integrated LED or replaceable bulb: most new pot lights have the LED built in, while older cans take a screw-in bulb or a retrofit LED module.
Pot light layout and installation: from spacing plan to drywall patching
Good spacing depends on the room rather than a fixed rule: the ceiling height, the beam angle and light output of the fixture, and what the space is used for. In a kitchen, lights usually follow the edge of the counters so the light lands in front of you, not behind your head. A living room wants softer, even light with a few fixtures washing the walls, and a hallway may need only a single row. Straight lines parallel to the walls make a ceiling look planned rather than peppered with holes.
The framing has the final say. Joists, trusses, ducts, plumbing and fire blocking decide where a hole can actually go, so the electrician checks the ceiling cavity before marking final positions. Separate switches or dimmers for each group of lights, such as the counter row and the dining area, give far more flexibility than one switch for the whole room.
- Marking and cutting: positions are checked against the framing, and each hole is cut to the size the fixture calls for.
- Running cable: in a finished ceiling, cable is fished from hole to hole and down to the switch, with small access openings where framing blocks the path.
- Connecting and mounting: each fixture is connected in its housing or in the junction box supplied with it, then clipped or clamped into the ceiling.
- Testing: circuits, switches and dimmers are checked before anything is closed up.
- Drywall patching: access openings and the old fixture's hole are patched, taped, sanded and painted; many electricians leave this to a drywall repair contractor, so ask who handles it before work starts.
Dimmers for LED pot lights: avoiding flicker, humming and a faint glow when off
Each LED pot light has a small electronic driver, and the driver and the dimmer have to work together. When they don't, lights flicker at low settings, hum, jump on at a high level or glow faintly when switched off. Choose fixtures marked dimmable, and check the fixture maker's list of compatible dimmers before buying either one. A dimmer also has a maximum LED load, and a long row of fixtures on one control can exceed it.
Some fixtures let you select the colour temperature with a small switch on the driver, which makes it easy to match every light in the room, and some offer a warm-dim setting that turns warmer as it dims. Settle these choices before the ceiling is closed: the switch is often reachable only through the hole.
Recessed lights on a top-floor ceiling: IC-rated airtight housings and the attic air barrier
On a ceiling below the attic, every pot light is a hole through the insulation and the air barrier. Natural Resources Canada cautions that standard recessed lights are difficult to air seal and can become a fire hazard if covered with insulation, and recommends approved airtight fixtures or covers that can safely go under insulation. That means an IC-rated housing labelled airtight, or a wafer fixture approved for the location.
Warm, humid air leaking around a poorly sealed fixture can condense in the cold attic, leaving frost on the roof sheathing in winter and stains around the light when it melts. When lights are added under an attic, or the attic is being reinsulated, have the electrician and the insulation contractor coordinate so every fixture is sealed at the ceiling and the insulation is put back around it.
Pot light rules: ESA notification, CMEQ licensing and fire separations such as garage ceilings
Adding pot lights is regulated electrical work. In Ontario, a Licensed Electrical Contractor files a notification with the Electrical Safety Authority before starting, and ESA issues a Certificate of Acceptance to whoever filed once the work passes; ask the contractor for a copy. In Quebec, the work goes to a contractor licensed through the Corporation des maîtres électriciens du Québec (CMEQ).
Some ceilings do more than hold lights. The ceiling between an attached garage and the rooms above it, or between a secondary suite and the main home, is built as a fire separation meant to slow a fire and keep fumes out of living space. Every hole cut in it has to keep that protection intact, whether through fixtures or enclosures suited to the assembly or surface-mounted lights instead. Raise it with the electrician before planning pot lights in a garage, and check with your municipal building department if you don't know how the ceiling was built.
Upgrading old pot lights: LED retrofit module or a new fixture?
Many homes still have older cans with halogen or incandescent bulbs that run hot and burn out often. When the housing is sound, rated for its location and not under an attic, an LED retrofit module that plugs into the existing socket and clips into the can is often a tidy upgrade, provided it is certified for use in that type of housing.
A new fixture is the better choice when an old housing under an insulated attic is not IC-rated or airtight, when lights keep shutting off from overheating, when the housing or wiring shows heat damage, or when you want to move or add lights. The electrician removes the old can and either reuses the opening or patches it if the new layout moves the fixture.
Signs a pot light needs an electrician: cycling off, scorch marks and frost stains
- A light that shuts off and comes back on by itself, often an older fixture overheating and tripping its thermal protector.
- Discoloured or scorched trim, a burning smell, or a socket that looks melted.
- Flicker or buzzing that persists after changing the bulb and checking dimmer compatibility.
- Frost, water stains or peeling paint around fixtures on a top-floor ceiling, a sign of warm air escaping into the attic.
Pot Lights: frequently asked questions
How far apart should pot lights be?
There's no single right distance. Spacing depends on the ceiling height, the fixture's beam angle and light output, and whether the room needs even light or light aimed at counters and walls. Ask for a layout drawn to scale and check the fixture maker's spacing guidance for the model you pick.
Can pot lights be added without attic access?
Usually, yes. Slim LED wafer lights and remodel housings go in from below through holes in the drywall, and cable is fished between openings. Framing that runs the wrong way or fire blocking may call for a few access holes that are patched afterward.
Can I put pot lights in my garage ceiling?
Only with care when there are rooms above. That ceiling is built as a fire separation, and every opening must keep it intact. Ask the electrician which fixtures or methods preserve the separation, or consider surface-mounted lights instead.
Can I keep my old dimmer with new LED pot lights?
Often not. A dimmer designed for incandescent bulbs can cause flicker, humming or a faint glow when off. Have it replaced with a dimmer the fixture maker lists as compatible, with enough capacity for the number of lights it controls.
Who repairs the drywall after pot lights are installed?
Ask before the job starts. Some electricians patch their access holes, while many leave taping, sanding and painting to the homeowner or a drywall repair contractor. A careful layout with few access holes keeps that work small.
Sources
Written by the LokalMatch editorial team. Reviewed by Zubair Afzal on September 10, 2026. How we write and check our guides