Wondering what a house extension costs in Kent in 2026? Most guides give you a vague UK-wide range, which helps nobody decide. This one gives you real Kent prices, honest figures, and the hidden costs builders rarely mention up front.
Average house extension cost in Kent runs £50,000 to £90,000 for a single storey build. Double storey projects typically cost £85,000 to £160,000 all-in. Final price depends on size, specification, ground conditions, access, and your exact Kent location.
Below you will find current 2026 prices by extension type and size. You will also learn what a fair quote looks like, and where homeowners get caught out.
Quick Answer: House Extension Cost in Kent 2026
Single storey extensions in Kent cost £2,000 to £3,000 per square metre in 2026. For a 20m² to 30m² build, that works out at £50,000 to £90,000 all-in. Double storey extensions run £85,000 to £160,000. The three biggest cost drivers are size, finish specification, and ground conditions.
Kent Extension Cost Per Square Metre in 2026
Here are the current 2026 Kent extension rates by type. Figures cover shell build with mid-spec finishes, including windows, doors, electrics, plumbing, plaster, and decoration.
- Single storey rear extension: £2,000 to £3,000 per m² | Typical total £50,000 to £90,000 for a 20m² to 30m² build
- Single storey side return: £2,300 to £3,300 per m² | Typical total £25,000 to £45,000 for a 6m² to 12m² build
- Double storey extension: £1,900 to £2,800 per m² | Typical total £85,000 to £160,000 for a 40m² to 60m² build
- Wraparound extension: £2,200 to £3,200 per m² | Typical total £70,000 to £110,000 for a 25m² to 40m² build
- Over-garage or first floor: £1,800 to £2,500 per m² | Typical total £40,000 to £65,000 for a 20m² to 30m² build
Costs in Kent sit roughly 15% to 25% above UK averages. They also land 20% to 30% below central London rates, reflecting local labour demand and the region’s housing stock.
Note: the figures above exclude VAT at 20%, professional fees, and kitchen or bathroom fittings. We cover those separately below.
Cost of a Single Storey Extension in Kent
Expect £2,000 to £3,000 per square metre for a single storey extension in Kent in 2026. A typical 20m² rear kitchen-diner runs £50,000 to £65,000 all-in.
Most Kent homeowners build at 15m², 20m², 25m², or 30m². Here is what each size typically costs in 2026:
- 15m² rear extension: £32,000 to £48,000
- 20m² rear extension: £50,000 to £65,000
- 25m² rear extension: £58,000 to £78,000
- 30m² rear extension: £68,000 to £90,000
Your build quote covers foundations, structural steels, brickwork, the roof, insulated windows, external doors, electrics, plastering, and decoration. It does not include kitchen units, appliances, landscaping, or VAT.
Typical single storey projects take 12 to 18 weeks on site, assuming no planning delays or ground surprises.
See our extensions and additions service in Kent for project types we handle regularly.
Cost of a Double Storey Extension in Kent
Double storey extensions cost £1,900 to £2,800 per square metre in Kent in 2026. For a 40m² two-storey rear extension, expect £85,000 to £115,000 all-in.
Going up is actually cheaper per m² than going out. You share foundations and the roof across two floors, which spreads fixed costs.
However, total costs run higher because you are adding more floor area. Scaffolding, structural steels, and upper floor plumbing all push the final bill up.
Two-storey builds almost always require full planning permission. If you live in a semi or terrace, you will also need a Party Wall Agreement with your neighbours.
Timelines run 20 to 30 weeks on site, reflecting more complex structural work and more finishes to complete.
Side Return, Wraparound, and Kitchen Extensions in Kent
These three popular Kent extension types sit in the mid-range of costs. Kitchen extensions carry extra fees for cabinets, appliances, and specialist plumbing.
Side Return Extensions in Kent
Side return extensions in Kent cost £2,300 to £3,300 per square metre in 2026. Total cost typically lands between £25,000 and £45,000 for a 6m² to 12m² build.
They work best on Victorian terraces in Tunbridge Wells, Tonbridge, and parts of Medway. Most homeowners use the new space to widen a galley kitchen or create a dining area.
Why the higher per-m² rate? Fixed costs like foundations and roofing spread across fewer square metres on small builds.
Wraparound Extensions in Kent
Wraparound extensions cost £2,200 to £3,200 per square metre in Kent in 2026. Total costs typically run £70,000 to £110,000 for a 25m² to 40m² build.
L-shaped extensions combine rear and side additions in one go. They create generous open-plan kitchen, dining, and family spaces.
You get the best value per m² once you pass 25m². Foundation and roof costs spread across more usable floor area.
Kitchen Extensions in Kent
Kitchen extensions add £15,000 to £35,000 on top of the shell build cost in 2026. That figure covers the kitchen itself, including units, worktops, and appliances.
Mid-range kitchens with quartz worktops and soft-close units cost around £10,000 to £15,000. High-end kitchens easily exceed £25,000 for bespoke joinery and premium appliances.
Budget another £3,000 to £6,000 for professional installation and any new plumbing runs. Flooring and lighting typically add £2,000 to £4,000 on top.
What Drives Kent Extension Costs Up or Down
Six factors swing your final quote by thousands of pounds. Knowing them helps you spot a fair price and avoid surprises.
- Your exact Kent location. Tunbridge Wells, Sevenoaks, and Tonbridge run 10% to 15% higher than Maidstone, Medway, and Ashford. Labour demand is simply higher in west Kent.
- Ground conditions. Clay soil across the Kentish Weald often needs deeper or engineered foundations. That adds £2,000 to £6,000 to a typical project.
- Site access. Terraced streets and rural lanes with poor access slow trades down. Labour hours rise, and so does the total quote.
- Finish specification. Bi-fold doors, sliders, or standard windows swing costs by £4,000 or more. Premium tiles, flooring, and joinery have the same effect.
- Structural complexity. Knocking through load-bearing walls for open-plan living needs steelwork. Budget an extra £2,000 to £6,000 for RSJs and installation.
- Planning and heritage status. Conservation areas, National Landscapes, and listed buildings bring extra design and material costs.
That last point deserves its own section, because Kent has more heritage constraints than most English counties.
Kent Specific Cost Considerations: Conservation Areas, AONB, and Listed Buildings
Roughly 25% of Kent sits inside the Kent Downs National Landscape or the High Weald National Landscape. Many towns also carry conservation area status on top.
Canterbury, Tunbridge Wells, Sevenoaks, and central Maidstone have extensive conservation areas. These usually require matching brick, lime mortar on older walls, and heritage-style windows or doors.
Article 4 Directions remove Permitted Development rights in many Kent conservation areas. That means full planning permission for extensions that would otherwise skip it.
Listed buildings carry the strictest rules. Listed Building Consent runs alongside planning. It adds 8 to 16 weeks and £5,000 to £15,000 to your project cost.
Key Kent planning authorities include Maidstone, Tunbridge Wells, Tonbridge and Malling, Sevenoaks, Medway, Ashford, and Canterbury councils. Always check your local rules before you commission drawings.
Learn more at the Kent Downs National Landscape website.
Hidden Extension Costs to Budget For in Kent
Builders typically quote for the build itself. Other costs pile up around it, and most homeowners underestimate them. Factor these into your working budget from day one.
- Architect or architectural designer fees: 7% to 15% of build cost, or £2,000 to £6,000 fixed
- Structural engineer: £500 to £1,200
- Planning application fee: £258 for a householder application in England
- Building Regulations approval: £500 to £1,500
- Party Wall Agreement: £700 to £1,200 per neighbour for a surveyor
- Skip hire and permits: £300 to £700 per skip, depending on your Kent district
- Temporary kitchen or bathroom hire: £500 to £2,000 during the build
- VAT at 20%: added on top if your contractor is VAT registered
- Contingency: 10% to 15% of build cost for unforeseen issues
On a £70,000 build, these extras can add £12,000 to £25,000 to your total cost. Always verify current planning fees on the official Planning Portal before applying.
Request a free bespoke quote that spells every line item out clearly.
Do You Need Planning Permission for an Extension in Kent?
Many single storey extensions in Kent fall under Permitted Development and skip full planning. Rear extensions up to 3m for attached homes and 4m for detached homes usually qualify.
Building Regulations approval is always required, even when planning permission is not. That keeps your build structurally sound, thermally efficient, and safe.
Conservation areas often come with Article 4 Directions, which remove Permitted Development rights. Always check with your local planning authority before you commit to a design.
Full planning adds £2,000 to £4,000 in fees and drawings, with applications typically taking 8 to 13 weeks. Consider a Lawful Development Certificate for £129, which proves your build was legal and protects resale value.
Does a House Extension Add Value to a Kent Home?
Well built extensions typically add 10% to 20% to a Kent property’s value. Kitchen-diner extensions and loft conversions usually deliver the strongest returns.
Property values in Kent have risen steadily in recent years, according to the Nationwide House Price Index. That makes extending an attractive alternative to moving and paying stamp duty.
Do not over-spec for your area though. Spending £120,000 on a £280,000 Medway terrace will not return full value at resale.
Match your investment to the local property ceiling. A good Kent builder will tell you honestly when a spec pushes past sensible return.
Real Kent Extension Example: 25m² Rear Extension, Maidstone (2026)
The table below shows an itemised example quote for a 25m² single storey rear kitchen-diner extension in Maidstone. Mid spec finish, semi-detached property, clay soil foundations.
Build costs:
- Groundworks and foundations: £9,500
- Structural steels and installation: £4,200
- Brickwork and blockwork: £8,800
- Roof structure and covering: £5,700
- Insulation and internal walls: £3,100
- Windows and bi-fold doors: £8,500
- Electrics and lighting: £3,400
- Plumbing and heating: £2,800
- Plastering and finishes: £4,200
- Decoration and flooring: £3,800
- Skip hire and site management: £1,500
Build subtotal: £55,500
Additional costs:
- Kitchen supply and fit: £14,000
- Professional fees (architect, engineer): £4,500
- VAT at 20%: £14,800
All in total: £88,800
This reflects a typical Maidstone semi-detached extension at mid spec. Rural Kent builds, listed properties, or higher spec finishes will push the total up accordingly.
Want an itemised quote for your property? Contact our team or see examples of our past Kent extensions.
Frequently Asked Questions
How much does a house extension cost in Kent in 2026?
A single storey extension in Kent costs £50,000 to £90,000 for a 20m² to 30m² build in 2026. That works out at £2,000 to £3,000 per square metre. Double storey extensions run £85,000 to £160,000. Final price depends on size, specification, and ground conditions.
What is the cost per square metre for an extension in Kent?
Kent extensions cost £2,000 to £3,000 per m² for single storey in 2026. Double storey builds run £1,900 to £2,800 per m². Side returns cost £2,300 to £3,300, and wraparounds £2,200 to £3,200. Kent runs 15% to 25% above UK averages but below central London rates.
Do I need planning permission for an extension in Kent?
Under Permitted Development, many single storey extensions in Kent skip full planning. Rear extensions up to 3m for attached homes and 4m for detached homes usually qualify. Building Regulations approval is always required. Article 4 Directions in conservation areas may remove Permitted Development rights.
How long does a house extension take in Kent?
Allow 12 to 18 weeks on site for a single storey extension in Kent. Double storey extensions usually run 20 to 30 weeks. Planning approval adds 8 to 13 weeks upfront if required. Listed buildings, conservation area projects, and party wall agreements can extend timelines further.
Does an extension add value to a Kent home?
Yes, well built extensions typically add 10% to 20% to a Kent property’s value. Kitchen-diner extensions and loft conversions give the strongest returns. Over-spec builds on lower-value properties do not fully return at resale. Match your investment to your local market ceiling instead.
Get a Free Bespoke Quote for Your Kent Extension
Extending a home in Kent in 2026 is a significant but predictable investment. Costs fall between £50,000 and £160,000 depending on type, size, and spec. Knowing the ranges above helps you spot a fair quote and avoid inflated ones.
Founded in 2011 by Ben, BDC Construction has completed hundreds of Kent extensions. Our team brings over 20 years of hands-on experience. We give transparent, itemised quotes with no hidden surprises. We also cover planning, Building Regs, and trades under one roof.
Get in touch for a free bespoke quote. We will visit your Kent property and talk through what is realistic for your budget. Then we hand you a fully itemised proposal. Call 01622 946189 or use our contact form to start the conversation.
Thinking about extending your home in Kent? Tell us what you have in mind, and we will tell you honestly what it will cost.