You have outgrown the kitchen. The kids are sharing a room. You are tired of squeezing past the dining table. An extension feels like the answer.
Then the quotes arrive. One builder says £45,000. Another says £95,000. For what sounds like the same job.
This guide breaks down the real house extension cost in Kent for 2026. You will see honest price ranges, the factors that move them, and the hidden costs most builders will not mention until you are halfway in.
How Much Does a House Extension Cost in Kent? (2026 Average Prices)
A house extension in Kent typically costs between £1,800 and £3,200 per square metre in 2026. A standard 25m² single storey rear extension usually lands between £55,000 and £85,000 including VAT, professional fees, and finishes. Double storey builds work out cheaper per square metre but cost more overall.
Kent prices sit slightly above the UK average. Labour competes with London rates, and material delivery into rural areas adds cost. Postcodes around Sevenoaks, Tunbridge Wells, and Canterbury tend to sit at the higher end.
Here is a quick reference for typical 2026 Kent projects:
| Extension Type | Size | Typical Cost Range |
| Small single storey | 15m² | £32,000 to £55,000 |
| Standard rear extension | 25m² | £55,000 to £85,000 |
| Large kitchen extension | 40m² | £85,000 to £130,000 |
| Double storey side | 30m² | £80,000 to £130,000 |
| Large double storey | 60m² | £140,000 to £200,000 |
| Wraparound extension | 35m² | £95,000 to £155,000 |
Single Storey Extension Cost in Kent
A single storey extension in Kent generally costs £45,000 to £95,000 for a 20m² to 30m² build. Final price depends on finish level, glazing choices, site access, and planning constraints.
Most homeowners spend the bulk of their budget on three things. Foundations and groundworks. The structural shell. The kitchen and finishes inside.
Worked Example: 25m² Rear Kitchen Extension in Maidstone
Here is a real-world breakdown for a mid-spec rear extension in Maidstone:
- Groundworks and foundations: £9,000
- Structural shell (walls, roof, steel): £18,500
- Bifold doors and roof lantern: £7,500
- Plastering, electrics, plumbing: £11,000
- Kitchen units and worktops (mid-range): £12,000
- Flooring, decorating, snagging: £6,500
- Architect, structural engineer, building control: £6,000
- Contingency at 10%: £7,000
Total: approximately £77,500.
Swap mid-range finishes for high spec and the same footprint can hit £95,000. Drop to budget finishes and you can land closer to £58,000.
Double Storey Extension Cost in Kent
A double storey extension in Kent typically costs £80,000 to £180,000. Most homeowners are surprised to learn that doubling the floor space does not double the price.
Adding a second storey usually costs around 50% to 60% more than a single storey of the same footprint. The foundations, scaffolding, and roof are already paid for in the ground floor build.
A 30m² double storey side extension in Sevenoaks runs roughly £105,000 to £140,000. The same footprint as a single storey would cost £65,000 to £85,000. The extra space upstairs adds value fast.
What Affects the Cost of an Extension in Kent?
Five factors drive most of the price variation. Get clear on these before you compare quotes.
Size and Complexity
Square metreage sets the baseline. But complexity adds cost faster than size. Wraparound extensions, vaulted ceilings, and structural openings into the existing house all push the figure up.
Specification and Finish Level
Budget, mid, and high-spec finishes can swing the total by 30% to 50%. Bifold doors, roof lanterns, underfloor heating, and bespoke kitchens are the usual culprits.
Site Access
This is a real cost driver in rural Kent. A property down a narrow lane in the Weald can add £5,000 to £15,000 to the build. Skips, deliveries, and machinery all become harder.
Conservation Areas and AONBs
Kent has two Areas of Outstanding Natural Beauty: the Kent Downs and the High Weald. Conservation areas in Tunbridge Wells, Canterbury, and Faversham add planning complexity. Expect higher design fees and stricter material requirements.
Ground Conditions
Kent sits on a mix of clay, chalk, and greensand. Clay-heavy plots near the Weald often need deeper foundations. Chalk near the North Downs can need specialist surveys. Both add to groundworks cost.
Hidden Costs Most Builders Will Not Mention
This is where cheap quotes turn into expensive surprises. A genuinely accurate estimate includes every line below.
- Party wall agreements: £1,000 to £2,000 per neighbour for a surveyor.
- Building control fees: £600 to £1,200 depending on Kent council and project size.
- Architect and structural engineer fees: typically 8% to 12% of build cost.
- Asbestos surveys on pre-2000 homes: £300 to £600.
- Drain diversions or new soil pipe runs: £1,500 to £4,000.
- Scaffolding for sloping or restricted sites: £2,000 to £5,000.
- Decorating and snagging budget: 5% to 8% of build cost.
- Contingency: a non-negotiable 10% to 15% of total build cost.
If a quote does not show these as line items, ask why. They do not vanish just because they are missing from the page.
Do You Need Planning Permission for an Extension in Kent?
Many extensions in Kent fall under permitted development and do not need full planning permission. Single storey rear extensions up to 6m on detached homes (4m on semis and terraces) often qualify, provided you meet height and design limits.
Permitted development does not apply if your home is in a conservation area, an AONB, or has an Article 4 direction in place. Several Kent districts use Article 4 to restrict permitted development in specific streets.
You can check national rules on the GOV.UK Planning Portal. Always confirm with your local Kent district council before you finalise plans.
Full planning applications add roughly £200 to £500 in fees and 8 to 12 weeks to the project timeline.
How Long Does a Kent Extension Take to Build?
Most Kent extensions take 12 to 24 weeks on site, plus planning and design time before that.
- Single storey extension: 12 to 16 weeks on site.
- Double storey extension: 16 to 24 weeks on site.
- Pre-build phase (design, planning, party wall): 3 to 6 months.
From first call to finished kitchen is typically 9 to 12 months. Builders who promise much faster are usually skipping detail somewhere.
How to Get an Accurate Extension Quote
A good quote should itemise everything. Vague labour lines and missing contingency are the two biggest red flags.
Ask any builder for a detailed specification sheet alongside the price. It should list materials, fixtures, and finishes by name. If two quotes look very different, the spec sheet usually explains why.
Be cautious of fixed-price quotes given without a site visit or detailed brief. They are not really fixed. They are estimates dressed up to win the job.
At BDC Construction, every quote is built from a site visit, a detailed spec, and 20 years of Kent pricing data. You can request a free, no-obligation quote and we will walk you through every line.
Frequently Asked Questions
Is a house extension worth it in Kent?
Yes, in most cases. A well-built extension in Kent typically adds 15% to 25% to the property value. Kitchen extensions and double storey side returns offer the strongest return. The added living space often outweighs the cost when you stay in the home for five years or more.
How much value does an extension add to a Kent home?
A single storey rear extension in Kent usually adds £40,000 to £80,000 in property value. Double storey extensions can add £80,000 to £150,000. The exact uplift depends on local property prices and quality of finish.
Can I live in my house during the extension build?
Most homeowners stay in the property for single storey rear extensions. Kitchen extensions are harder, as you will be without a kitchen for 6 to 10 weeks. Double storey builds with structural openings often warrant moving out for the noisy phases.
Do I pay VAT on a house extension in Kent?
Yes, standard VAT at 20% applies to most extension work in the UK. Some new-build elements within an extension can qualify for reduced rates in specific cases. Always confirm with your builder and accountant before assuming a VAT saving.
Get a Quote You Can Actually Trust
A well-planned extension in Kent at 2026 prices, properly quoted, should hold its budget within a tight contingency. The number you sign off should be close to the number you pay.
That only happens when the quote is honest from day one.
BDC Construction has been building extensions across Kent for over 20 years. Every quote is itemised. Every timeline is realistic. No hidden surprises mid-build. Request your free, no-obligation quote and find out what your project should actually cost.