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Kitchen Extension Planning Checklist UK: Costs, Steps and Rules

Permitted development does not cover as much as most people think. That assumption, made early and not checked until later, is the single most common reason kitchen extension projects in Surrey and Sussex lose months before a spade goes in the ground.
 
This checklist covers what you actually need to think through, in the order it matters.
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Dark grey handleless kitchen with stone worktop and L-shaped layout in a modern apartment

Step One: Be Clear on What You're Actually Building

Before costs, before architects, before anything, get specific about what the extension is doing. Is it adding square footage to an existing kitchen? Creating a kitchen-diner by opening up the ground floor? Replacing a dark galley with something that connects properly to the garden?
 
The answer shapes everything that follows. A single-storey rear extension is a different project, in terms of cost, planning, and complexity, from a side-return or a wraparound.

The Most Common Types of Kitchens

Single-storey rear extension.

The most common. Extends the back of the house into the garden. Usually used to create an open-plan kitchen-diner or to add a utility room alongside.

Side-return extension.

Fills the narrow gap beside a terraced or semi-detached property. Common in period homes across Surrey and Sussex. It can dramatically change the feel of a kitchen without a large footprint.

Wraparound extension.

Combines rear and side-return into an L-shape. More expensive, more transformative.
Two people reviewing architectural floor plans and kitchen layout drawings at a table

Step Two: Understand Planning Permission and Permitted Development

Most single-storey rear extensions fall under permitted development, meaning no full planning application is needed. But the limits are specific and easy to fall foul of.
 
In England, a detached house can extend up to 8 metres from the original rear wall under the neighbour consultation scheme. For semi-detached and terraced properties that drop to 6 metres. Those figures assume the extension is single-storey, the height doesn’t exceed 4 metres, materials match the existing house, and the property isn’t in a conservation area or AONB.
 
Parts of Dorking, Reigate, and several Surrey villages sit within conservation areas where permitted development rights are restricted or removed entirely. Check with your local planning authority before assuming anything. The Planning Portal is the right starting point: www.planningportal.co.uk
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Step Three: Budget Realistically

Kitchen extensions in Surrey and the South East cost more than national averages suggest. A basic single-storey rear extension, shell-only with no fit-out, typically starts at £25,000, depending on size, ground conditions, and specification. Add a new kitchen and the total picture changes considerably.

Real-world ranges for this part of the country:

Modest single-storey extension with mid-range kitchen: £45,000 to £75,000. Larger extension with premium kitchen and finishes: £80,000 to £150,000 and above

What pushes a project toward the top of those ranges? Poor ground conditions, older properties with drainage complications, high-specification glazing, structural steelwork, and premium kitchen finishes all add up quickly. Anyone quoting significantly below these figures deserves a close look at exactly what is included.

What the Budget Needs to Cover

-Architect or designer fees
-Structural engineer required for most extensions
-Planning application fees, if applicable
-Building regulations fees
-The build itself, covering foundations, structure, roof, glazing, plastering, electrics and plumbing
-Kitchen supply and installation
-Flooring, decoration, and finishing
-A contingency of at least 10 to 15 per cent

That last line is not optional. Unexpected costs are common in older properties. Poor ground conditions, hidden drainage runs, structural surprises behind plasterwork. Budget for them before you start, not after.

Step Four: Get the Right People Involved in the Right Order

The sequence matters more than most people realise. A common mistake is going to a kitchen designer first, falling in love with a layout, and then discovering the building work needed to achieve it costs twice the expected budget.
The better order:
  1. Initial consultation with a design and build company or architect to establish what is actually feasible
  2. Structural engineer assessment of whether walls are coming down or a significant extension is planned
  3. Kitchen design within the confirmed space and confirmed budget
  4. Building work, then fit-out
Kitchen designer discussing worktop samples and floor plans with a couple at the Lime Designs showroom

Why One Company Handling Both Makes a Difference

When building work and kitchen design are managed separately, things fall through the cracks. Layouts get designed without accounting for structural constraints. Build programmes don’t allow for kitchen delivery lead times. Change requests mid-project create delays because two separate companies have to agree on them.
At Lime Designs, both sides sit under one roof. The building team and the kitchen designers work from the same brief, to the same timeline. That is not a sales point. It is a practical difference that affects how smoothly a project runs.

What Our Customers Find

Amelia White used Lime Designs for a full kitchen transformation and said Jake took every requirement into account, from unit designs and worktop choices through to appliances, flooring, and finishing touches, from the first conversation right through to the fitted result. Communication was consistent throughout, last-minute changes were handled without fuss, and the finished kitchen looked, in her words, even better than she had imagined.

That kind of process only works when the planning stage is done properly. The details get sorted before anything goes on order.

Cream handleless kitchen with marble waterfall island, double ovens and oak herringbone flooring

Step Five: Building Regulations Are Separate From Planning Permission

Even when an extension doesn’t require planning permission, it still needs building regulations approval. The two are not the same, and both matter.

Building regs cover structural integrity, fire safety, insulation, ventilation, drainage, and electrics. Your contractor should manage the submission and inspections, but confirm it is included in any quote before you sign anything. The completion certificate issued at the end is important, particularly when selling the property.

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The Checklist: What to Confirm Before You Start

Work through this before any money changes hands.

Before planning:

-Confirmed the type of extension and what it needs to achieve

-Checked permitted development limits for your specific property type

-Verified whether your property is in a conservation area or an AONB

-Speak to your local planning authority if there is any doubt.

Before planning:

-Have at least two detailed quotes covering the same scope.

-Confirmed structural engineer involvement is included or arranged.

-Checked that the building regulations submission is part of the contract

Asked explicitly what happens if costs change mid-project

Before the build starts:

-Kitchen design signed off, and materials on order.

-The programme is agreed in writing with clear milestones.

-Single point of contact confirmed for the duration

-Contingency budget set aside and not allocated to any other purpose.

Start With a Free Consultation

Book a free consultation at your home or in our Dorking showroom, and we will properly assess your space, talk through what is feasible, and give you an honest picture of costs and timescales before anything is committed. No obligation to go further.
 
Call: 01306 884666
Email: enquiries@lime-designs.co.uk
Visit: 286 High Street, Dorking, RH4 1QT.
 

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