The common layouts are a galley run with an island, an L-shape with the sink on the glazed wall, and a broken-plan arrangement using a partial divide. What matters more than the layout is deciding it before first fix, because sockets, waste runs, water and extract positions all follow from it — and changing them afterwards means opening finished work.
- Decide the layout before first fix. After that, every change costs real money.
- Extract is the most-regretted omission. Plan the duct route early.
- A fully glazed south-facing rear overheats without shading or solar-control glass.
- Keep a worktop run out of the main walking route between door and garden.
Layouts that work in a rear extension
Galley run with an island
Units along one wall, an island parallel to it. Works well in a rectangular extension of reasonable width, keeps the glazed rear wall clear of units, and gives a natural division between cooking and sitting. Needs enough width that the gap between run and island is comfortable with a dishwasher door open — squeezing this is the commonest regret.
L-shape with the sink on the glazed wall
Units on two adjacent walls, sink under or beside the rear glazing. People like washing up with a view, and it keeps the cooking wall solid for extract. The trade-off is plumbing and waste running to the rear of the extension, which has drainage implications worth checking early.
Broken plan rather than open plan
A partial divide — a half-wall, a change of level, a structural pier left in place, or tall units used as a divider — between the kitchen and the sitting area. It gives separation of noise, smell and mess without closing the space off, and it is increasingly what people ask for after living in a fully open-plan room.
Keeping the kitchen in the original room
Worth considering and rarely considered. Put the new dining and living space in the extension and keep the kitchen where the services already are. It is substantially cheaper, it avoids moving drainage, and on a side return project it can mean the darkest part of the plan is used for the function that needs light least.
Decide before first fix
This is the single most useful thing on this page.
Once the shell is up, the trades need to know where everything goes. Socket positions, appliance locations, water supply and waste runs, extract ducting, lighting circuits, underfloor heating zones — all of it is set at first fix, before plastering.
A change after first fix means chasing out new plaster, lifting floor screed, or re-running pipework. A change after second fix means doing it twice. Neither is impossible and both cost money that was avoidable.
So the sequence that saves money is: settle the kitchen layout, get the supplier's plan with appliance positions marked, and give that to the builder before first fix starts. Not "roughly a run along that wall" — actual positions.
This is also the most common cause of a contingency being spent, and it is the one entirely within your control.
The details people wish they had planned
- Extract. The most regretted omission. A recirculating hood does not remove moisture, and moisture is what causes condensation. A ducted extract needs a route to an outside wall, and that route has to be designed in, not found later.
- Sockets. Always more than you think, and specifically on the island, which needs a supply running through the floor — so it must be decided before the slab or screed.
- Bin storage. Rarely planned, always needed, and awkward to retrofit into a fitted run.
- The door swing. Where the back door opens, and whether it fouls a unit or the walking route.
- Lighting layers. Task lighting over the worktops as well as general lighting, with separate switching. A single ceiling grid over a large room is flat and unhelpful.
- The walking route. Keep the path from the hallway to the garden door clear of the working area, or people will walk through your cooking.
- Where the fridge door opens, and whether it blocks the walkway when open.
Glazing, light and overheating
Large rear glazing is what most people want from a kitchen extension, and it needs thinking about in two directions.
Light. Glazing at the rear lights the rear. It does not light the middle of the plan, which is where a rear extension most often goes dark. Rooflights over the deepest part are what solve that, and they are more effective per square metre of glass than a bigger rear opening.
Heat. A fully glazed south or west-facing rear elevation will overheat in summer. Building Regulations address overheating in new dwellings, and while an extension is a different case, the physics is identical. The responses are solar-control glass, an overhang or brise-soleil, external blinds, or simply orientating the largest glazing away from the worst exposure.
A glazed box that is uncomfortable for three months of the year is a common and avoidable outcome. Raise orientation at design stage.
Where the money goes
| Element | Share of a kitchen extension budget | Note |
|---|---|---|
| Shell — groundworks to plaster | The largest single block | Priced per square metre |
| Glazing | Often the biggest single item after the shell | Bifolds and sliders especially |
| Kitchen units and worktops | Highly variable | The widest spread of anything |
| Appliances | Variable | Usually client-supplied |
| Flooring | Moderate | Often outside the build quote |
| Electrics and plumbing | Moderate | More than a standard room |
| Decoration | Small | Often taken on by the client |
The kitchen itself has the widest spread of any element. Two extensions with identical shells can differ by a large margin on the fit-out alone, which is why kitchens are usually a provisional sum.
What it costs
These are the extension figures published across this site:
| Job | Typical Coventry guide price | Notes |
|---|---|---|
| Build cost | £1,500–£2,500 per m² | Spec dependent |
| Single-storey extension | £20,000–£60,000 | Size & finish dependent |
| Double-storey extension | £100,000+ | Larger projects |
| Average project | ~£30,700 | Across typical jobs |
Those are build figures. The kitchen, appliances and flooring usually sit outside them, which is worth confirming on any quote you compare — two builders carrying different provisional sums are not offering the same thing.
Bring the kitchen layout to the first conversation if you have one. It changes the services design and saves money later.
Frequently asked questions
When do I need to choose my kitchen?
Before first fix, and earlier than most people expect. Socket positions, appliance locations, water and waste runs, extract ducting and underfloor heating zones are all set before plastering. A change afterwards means chasing new plaster or lifting screed. Give the builder the supplier's plan with appliance positions marked.
Is open plan still a good idea?
It depends how you live. Fully open plan carries noise, cooking smells and visible mess across the whole space, which many people find wearing after a year. Broken plan — a half-wall, a level change, a structural pier, tall units as a divider — keeps the openness while giving some separation, and it is increasingly what clients ask for.
Do I need an extractor if I have bifold doors?
Yes. Opening doors in summer is not a ventilation strategy for the other nine months, and the moisture from cooking is what causes condensation. A recirculating hood filters smells but does not remove moisture. A ducted extract needs a route to an external wall, and that route must be designed in early.
Will a glass extension be too hot in summer?
A fully glazed south or west-facing rear elevation will overheat without something done about it. The answers are solar-control glass, an overhang or brise-soleil, external blinds, or orientating the largest glazing away from the worst exposure. Raise it at design stage, because retrofitting shading is expensive and usually looks it.
Should I keep the kitchen where it is?
It is worth considering and rarely considered. Putting the dining and living space in the extension and leaving the kitchen where the services already are is substantially cheaper, avoids moving drainage, and can mean the darkest part of the plan is used for the function needing light least.
Is the kitchen included in an extension quote?
Almost never as a supplied item — it is usually excluded or carried as a provisional sum, which is a placeholder to be replaced by the real cost. The kitchen has the widest cost spread of any element, so two quotes with different provisional sums are not comparable until you normalise them.
Bring the layout, not just the footprint
A kitchen plan at the first conversation changes how we design the services, and it is the cheapest decision you will make on the whole project.