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kitchen fit sequence

Lighting Plan for an Extension: Layout, Spacing and Timing

How to plan lighting for a single-storey rear extension: reflected ceiling plan, downlight spacing over worktops, Part P rules and when to decide it all.

The Extension Works 21 October 2026
Lighting Plan for an Extension: Layout, Spacing and Timing

Lighting Plan for an Extension: Layout, Spacing and Timing

Downlights and task lighting in an extension kitchen

A good lighting plan for an extension is decided on paper before the plasterboard goes up, not chosen from a catalogue at the end. You mark every light, switch and fitting on a drawing of the ceiling, line it up with joists, rooflights and the kitchen layout, and agree it with your builder and electrician while changes are still cheap. This guide shows you how, including where kitchen downlights should sit and what the electrical rules expect.

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TL;DR

  • Lighting is a drawing job first: a reflected ceiling plan shows where every fitting goes and flags clashes with joists, rooflights, vents and smoke alarms.
  • In a kitchen, plan from the worktop outwards. Put task downlights over the front edge of each run, roughly 1m to 1.2m apart, rather than in a neat grid across the room.
  • Downlights alone leave shadows. Add under-cabinet lighting as a separate task layer, plus softer ambient and accent light elsewhere.
  • A new circuit or any work in a kitchen is covered by Part P of the Building Regulations. Ask for the certificate before final sign-off.
  • Fix the plan before first-fix electrics. After that, adding fittings usually means opening up finished work.

Table of Contents

Why the lighting plan belongs in the design stage

Most people treat lighting as a shopping decision: pick some spotlights, pick a pendant, done. In practice the number of lights matters far less than where they go and when you decide.

An extension has a lot of competing things in the ceiling: joists, a rooflight or two, extractor ducting, smoke alarms, perhaps a steel beam where the old back wall came out. My Home Extension makes the same point from the homeowner’s side: discuss your requirements with your building professionals early, before electrical work starts, or you may reach a stage where certain fittings can no longer be added without disruption.

The practical rule is simple. Every light, switch, socket and control you want should be on a drawing before the electrician starts first fix. That is the moment cables go in and walls and ceilings are still open.

Start with a reflected ceiling plan

A proper lighting plan is not a list of fixtures. It is a reflected ceiling plan (RCP): a drawing that treats the ceiling as if it were a mirror on the floor, so you see the ceiling layout as if looking up at it, drawn flat like a normal floor plan. It shows light positions alongside the structure and services they have to coexist with.

On your RCP, mark:

  • every downlight, pendant drop and wall light, using a clear symbol key
  • rooflights, lantern roofs and any sloping ceiling sections
  • joist direction and any beams or steelwork
  • extractor outlets, vents and smoke or heat alarms
  • switch positions and which switches control which lights

The benefit is catching clashes on paper. A downlight that lands directly under a joist, or on top of a vent, is a five-minute fix on a drawing and a costly one on site.

If you are also working out the rest of your drawings, our guide to extension planning drawings explains which plans you will meet and what each is for. Lighting layouts are normally a separate, more detailed layer on top of those.

Think in layers: ambient, task and accent

Designers recommend layering light in three categories rather than relying on one set of ceiling spots:

Layer What it does Typical examples in an extension
Ambient General illumination of the room Ceiling downlights, a central pendant on a dimmer
Task Focused light for jobs Under-cabinet strips, lights over the hob and sink, a reading light
Accent Picks out features Wall washers, plinth lights, a lit alcove, light on a brick feature wall

The common mistake in open-plan extensions is to cover the whole ceiling with ambient spots and call it done. Over a dining table that feels flat and harsh. A pendant on its own switch, with a dimmer, does more for the room than six extra downlights.

It also helps to put each layer on its own switch or dimmer circuit. You can then run the room bright for cooking and low for the evening, without everything coming on at once.

Downlight spacing in the kitchen

The kitchen is where lighting plans most often go wrong, and it is the question readers ask most: how far apart should the downlights be?

Plan from the worktop, not the room centre

Lighting specialists describe good kitchen design as worktop-first. A symmetrical grid across the ceiling looks tidy on a drawing, but it often leaves the work surfaces in shadow, because when you stand at the counter your body blocks the light coming from behind you.

The fix is to put the downlights where the work happens:

  1. Sketch the kitchen from above, marking worktops, sink, hob and any island or peninsula.
  2. Draw a line along the front edge of every run of worktop. LightHub Direct’s kitchen guide places the task downlights along this line, spaced roughly 1m to 1.2m apart.
  3. In practice that puts each row about 50 to 60cm out from the wall cabinet fronts, according to the same lighting guidance, so the light falls on the front edge of the worktop and not behind you.
  4. Apply symmetry to those rows, not to the centre of the room. Rows that follow the cabinet runs look deliberate and light the right places.

Check your spacing against the beam

Spacing also depends on the fitting. A rule of thumb from Your Light Informer: space fittings at roughly the beam diameter on the surface you care about, or about 0.8 times that for a softer, more even result. A narrower beam needs lights closer together to avoid scalloped pools of light. A wider beam can be spaced further apart but gives less contrast.

How beam width affects downlight spacing

That is why a spacing figure from a website is a starting point. Your ceiling height, beam angle and finish all change the answer, and your lighting designer or electrician can check it against the actual fittings.

Downlights alone will not fix shadows

Even well-placed downlights cannot fully remove worktop shadows. Lightguru’s guidance is that you need under-cabinet lighting as a dedicated task layer, with the downlights doing the general work. If you are choosing between the two on a budget, put the under-cabinet light in first. It sits closest to the work and cannot be blocked by your head or shoulders.

Worked example: a 4.5m kitchen-diner

Imagine a rear extension with a kitchen run of 4.5m along one wall and a dining area beside the bifold doors. The method gives you:

  • one row of task downlights following the front edge of the worktop, set about 50 to 60cm from the cabinet fronts and spaced at roughly 1m to 1.2m, which suggests four fittings for the 4.5m run
  • under-cabinet strips along the full length of the wall units
  • a separate switch for a pendant, or a pair of pendants, over the table
  • a dimmable circuit for any wall lights or accent lighting near the seating area

That is an illustration of the method, not a specification. Your own layout, island and rooflight positions will change the numbers. If your kitchen-diner is still at the ideas stage, our kitchen diner extension ideas piece covers layouts that avoid planning delays.

Working with rooflights and natural light

Extensions often bring in a lot of daylight, which changes the lighting plan. Rooflights, lantern roofs and glazed doors mean you rely less on artificial light by day, and more on layered, low-level light at night, when large glass areas turn into dark mirrors.

Practical points to put on the RCP:

  • Keep downlights clear of rooflight upstands and frames, which are visible on the drawing and not under the plaster.
  • On sloping or vaulted sections, fittings need more thought than on a flat ceiling. A forum thread is no substitute for checking with your building control body or designer on what is acceptable, so ask early.
  • Give the glazed side of the room its own lighting circuit, so you can dim or switch it off in the evening.

For more on bringing in daylight in a compact footprint, see our guide to small rear extension ideas that maximise light and value.

The electrical rules you need to know

Lighting in a new extension is electrical work, and electrical work in homes in England is covered by Part P of the Building Regulations.

What that means in practice:

Before final sign-off, ask your project manager or builder for the electrical certificate from a registered electrician, or the building control record if the work was notified. You will be asked for these when you sell, and missing paperwork is a common cause of delay. Our guide to Building Regs for extensions in England explains how this fits into the completion certificate.

If you are adding a lot of new circuits, such as under-floor heating, a kitchen and extra lighting, check whether the consumer unit can cope. We cover that in our piece on fuseboard upgrades for extensions.

For the exact rules on your project, ask your electrician or your local authority’s building control team. Do not rely on a general guide for what is notifiable.

A note for families

If you have young children, the lighting plan is also a safety plan. Think about night-time routes from bedrooms to the new kitchen, and put low-level or sensor lighting where a child will walk. If the route involves stairs, child-safe stair handrail options are worth looking at while the house is being reworked, rather than after.

When to decide: a sequence that avoids rework

The order of events matters more than most people expect. A typical sequence for a kitchen in a new extension looks like this:

  1. Design stage: agree the kitchen layout, rooflights and ceiling heights. Draw the first RCP.
  2. Before construction: confirm fittings, beam angles and any dimming or smart controls. Finalise switch positions.
  3. First fix: the electrician runs cables to the marked positions while ceilings and walls are open.
  4. Plastering and decorating: holes are cut for downlights only after the ceiling is finished, to the marked positions.
  5. Kitchen fit: units and worktops go in. Fitting timelines vary, but a typical kitchen installation runs over several days, from strip-out and base units to worktops and appliances.
  6. Second fix and testing: fittings are connected, circuits tested and certificates issued.

The cost of changing your mind rises sharply at step 3. Moving a light before first fix is a line on a drawing. Moving it afterwards can mean cutting into a finished ceiling.

Our perspective

We build single-storey rear extensions, and design, planning, structure and construction all sit with one in-house team. That is why we treat lighting as a design decision, not a finishing touch.

Our live 3D model lets you see the room as it takes shape, which is exactly when to think about where you will stand, cook and sit. Lighting that suits those places is much easier to agree when you can see them. The pattern we see in extension projects is simple: the plans that work are the ones where the homeowner decided early where the table, island and sofa would go, and the lighting followed that.

Our perspective — overview diagram

Our advice is to be a little boring about the kitchen. Light the worktops first, add under-cabinet strips, put the pendant on its own dimmer, and only then decide what the ceiling should look like. A symmetrical grid is the thing people regret most.

And keep the paperwork. A tidy electrical certificate at completion saves arguments later.

— Esskay

How we handle this when you book with us

With The Extension Works you get instant online pricing, a live 3D model of your single-storey rear extension and a fixed, VAT-inclusive price, with design, planning and building control managed by a dedicated in-house team. That makes it simple to settle the layout, including where the kitchen and lighting go, before work starts. Booking carries a one-off £499 booking fee. You can start with the instant extension quote tool, and if you want to see how the design side works first, read our guide to single-storey rear extension design.

Lighting plan checklist

Bring this to your designer and electrician:

  • A sketch of the room with worktops, sink, hob, island, table and seating marked
  • Rooflight and lantern positions, and joist direction
  • Where the rows of task downlights go, along the worktop front edges
  • Under-cabinet lighting runs and their switch
  • Pendant positions over the table and island, on their own switch
  • Dimmable circuits for living and dining zones
  • Switch positions at each door, and two-way switching where you enter from more than one side
  • Smoke and heat alarm positions, extractor outlet, and any vents
  • A request for the Part P certificate or building control record at handover

FAQ

How many downlights do I need in a kitchen extension?

There is no fixed number. Plan along the front edge of each worktop run, with fittings roughly 1m to 1.2m apart, then check the spacing against the beam angle of your chosen light. Add under-cabinet lighting for the work surface itself, and keep the dining area on a separate dimmable circuit.

How far from the wall cabinets should downlights be?

About 50 to 60cm from the front of the wall cabinets is the usual guidance, so the light lands on the front edge of the worktop. That stops you standing in your own shadow while preparing food.

Do I need Building Control approval for new lighting in an extension?

Often yes. Work in a kitchen, or on a new circuit, must be notified to building control or certified by an electrician registered with a competent person scheme. A full extension usually involves a new circuit, so confirm with your electrician and local authority.

When should I finalise the lighting plan?

Before first-fix electrics, ideally at design stage alongside the kitchen layout. Once ceilings are boarded and plastered, adding or moving fittings is harder and costlier.

Sources