Kennington hides a landlord that most extension guides never mention: the Duchy of Cornwall. A large slice of SE11, from Courtenay Square to Cardigan Street and stretches of Kennington Road, is Duchy leasehold, and a Duchy lease needs a licence to alter before any structural work. Layer that on top of the Georgian terraces, the conservation areas and the odd listed house, and consent, not construction, is what shapes a Kennington project.
This guide gives real 2026 figures for a home extension in Kennington. It covers cost, the consent route through both Lambeth and the Duchy, the timeline and the return. Numbers come from Buildaway's SE11 quoting data, the London Borough of Lambeth, the ONS, Nationwide and GOV.UK.
• Cost (2026): £57,000-£116,000 single-storey rear; £116,000-£198,000 two-storey; £176,000-£300,000 wrap-around with loft dormer.
• Timeline: 5 to 11 months from first call to handover. A single-storey build takes 9-15 weeks on site.
• Consent: Duchy of Cornwall leaseholds need a licence to alter alongside planning; conservation areas and listing are widespread.
• ROI: Adding 10% more floor space adds about 5% value (Nationwide). On an £860,000 Kennington terrace (ONS Lambeth data), that is around £43,000.
• Areas: SE11, from Cleaver Square and Kennington Park to the Oval.
How Much Does a Home Extension Cost in Kennington in 2026?
A home extension in Kennington costs £57,000 to £116,000 in 2026 for a single-storey rear extension. A two-storey side or rear extension costs £116,000 to £198,000. A wrap-around with a loft dormer costs £176,000 to £300,000. Full-width schemes run £278,000 to £465,000 and beyond. Each band covers design, structure, finishes and VAT.
These are Buildaway's 2026 quoting bands for SE11. Rates sit toward the higher end of South London because of Georgian detailing, two-sided party walls and, on Duchy leases, the extra licensing work. For a line-by-line breakdown, see our Kennington extension cost guide.
| Project type | New space | All-in range | Build rate per m² | On site |
|---|---|---|---|---|
| Single-storey rear | 10-20 m² | £57,000-£116,000 | £2,700-£3,700 | 9-15 weeks |
| Two-storey side or rear | 18-34 m² | £116,000-£198,000 | £2,500-£3,400 | 15-24 weeks |
| Wrap-around with loft dormer | 28-48 m² | £176,000-£300,000 | £3,000-£4,200 | 18-28 weeks |
| Full-width or lower-ground remodel | 40-80 m² | £278,000-£465,000+ | £2,000-£3,100 | 20-32 weeks |
Where is the money spent? On a two-storey terrace scheme the groundwork and structure take the biggest share, with fees and contingency smaller, and Georgian repairs or a Duchy licence adding to the fee line. The chart shows the split Buildaway sees most often in SE11.
Bars scaled to the largest share. Source: Buildaway 2026 project data for SE11 extensions.
What Does a Luxury Home Extension in Kennington Include?
A luxury home extension in Kennington usually opens the rear of a Georgian terrace with slim structural glazing and a lower-ground lightwell, keeping the front and sashes exactly as the conservation area found them. Restored joinery and heritage brick feature throughout. Structural glazing runs £6,000 to £24,000, and the kitchen fit-out often takes a quarter to a third of the budget.
The distance between the two ends of a band is specification. A simple rear addition sits near the lower figure; frameless glazing, a reworked lower-ground floor, stone surfaces, hand-made joinery and, on a leased house, Duchy-compliant detailing lift it to the upper one. Our Kennington kitchen renovation guide prices the kitchen half in detail.
What Fees Sit Outside the Build Cost?
Set aside £6,000 to £18,000 for the professional and statutory side, plus the Duchy licence fee on a leased house. The list runs to designer, structural engineer, the application, building control inspection and party wall surveyors, and a mid-terrace typically needs two of the last. England's householder planning fee is £548 from 1 April 2026, and each adjoining owner served costs £2,200 to £6,000.
The planning fee is set nationally (GOV.UK), and VAT at 20% applies to most extension work. A conservation-area house needs a heritage statement, a listed one needs listed building consent, and a Duchy lease needs a licence to alter with its own surveyor's fee. Buildaway sets all of these out in the quotation from the start.
Which Kennington Homes Can Be Extended?
Most Kennington houses can be extended, but tenure decides the process. A freehold Georgian or Victorian terrace extends to the rear within the conservation area. A Duchy of Cornwall leasehold can too, but needs the estate's licence to alter first. Converted flats have no permitted development rights and need the freeholder's consent.
| Property type | Where in Kennington | What is realistic |
|---|---|---|
| Freehold Georgian terrace | Around Cleaver Square and Kennington Road | Rear, lower-ground remodel, lightwell |
| Duchy of Cornwall leasehold | Courtenay Square, Cardigan Street, Denny Street | Rear, with a licence to alter alongside planning |
| Victorian terrace | Streets toward the Oval and Walworth | Rear, side-return, loft dormer |
| House converted into flats | Across SE11 | Ground-floor rear only, full planning |
| Purpose-built flat | Near Kennington and the Oval | Internal remodel with freeholder consent |
Where building out is limited, going down or up often is not. A lower-ground remodel or a loft conversion in Kennington can each add a room without altering the protected front, subject to the same conservation and, where relevant, Duchy consents. Buildaway can quote the options side by side.
How Does the Duchy of Cornwall Licence Work?
If your home is a Duchy leasehold, you need the estate's licence to alter before structural work, in addition to planning. It is a separate consent, run by the Duchy's surveyors, that checks the proposal against the lease and the estate's standards. It does not replace planning; it sits beside it, and it can hold up a start if left until after permission.
The practical answer is to run them together. Buildaway prepares one set of drawings and submits the Lambeth application and the Duchy licence within a fortnight of each other, so the two consents proceed in parallel. Queued instead, they can add roughly two months to the programme, which is why identifying the lease at feasibility matters so much on a Kennington project.
Do You Need Planning Permission for a Home Extension in Kennington?
Usually, yes. A freehold house outside a conservation area can add a 3-metre rear extension under permitted development, but most of Kennington is designated, flats have no such rights, and listed houses need listed building consent. On a Duchy lease a licence to alter is also required, so full planning plus estate consent is the standard route.
The national rules are on the Planning Portal and in the GOV.UK technical guidance. Lambeth and the Duchy then add their layers.
- Duchy of Cornwall leases. Leaseholders need a licence to alter from the estate alongside planning (Duchy of Cornwall).
- Conservation areas. Cleaver Square, Kennington and the wider SE11 area control external change (Lambeth).
- Listed buildings. Some Georgian houses are Grade II. Unauthorised work to a listed building is a criminal offence (Historic England).
- Congestion Charge and ULEZ. All of SE11 is within the ULEZ, and the northern edge touches the Congestion Charge.
- Party walls. Terraces share walls on both sides, so notices often go to two owners (GOV.UK).
- Drains and sewers. A build within 3 metres of a public sewer needs a Thames Water build-over agreement.
No matter the planning route, Building Regulations approval is compulsory (GOV.UK). Where the work is permitted development, still obtain a lawful development certificate, since a buyer's conveyancer will expect to see one. Our UK extension planning guide sets out the national rules in full.
How Long Does a Home Extension Take in Kennington?
Allow five to eleven months from first call to handover. A single-storey rear extension takes 9 to 15 weeks on site. A two-storey extension takes 15 to 24 weeks. A wrap-around with a loft dormer takes 18 to 28 weeks. Planning, any Duchy licence and two-sided party wall awards take up most of the time before the build begins.
| Stage | Typical timing | Kennington factor |
|---|---|---|
| Survey and feasibility | Weeks 1-3 | Identify any Duchy lease, listing and conservation area |
| Design and structural scheme | Weeks 2-7 | One drawing set for planning and the estate licence |
| Planning and Duchy licence in parallel | Weeks 5-16 | Submit both within a fortnight to avoid queueing |
| Building control, party wall, ordering | Weeks 8-18 | Two-sided party wall on a terrace |
| Build on site | 9-32 weeks | Parking permits, ULEZ-compliant deliveries |
Your home extension timeline in SE11 hinges on running planning and the Duchy licence together. Leave the estate licence until after planning and you can lose around two months; submit both from the same drawings and the front end stays tight.
How to Plan a Home Extension in Kennington
Take these steps in order. On a Duchy estate the first and fifth are what keep the programme moving.
- Check for a Duchy of Cornwall lease. Confirm whether your home is a Duchy of Cornwall leasehold, which needs a licence to alter.
- Check the constraints. Look up conservation area, Article 4 and listed building status for your address.
- Commission a measured survey. Accurate drawings stop design errors reaching site.
- Agree a design and structural scheme. Fix the layout, glazing and steelwork before pricing.
- Run planning and the estate licence together. Submit the Lambeth application and the Duchy licence from the same drawings within a fortnight.
- Serve party wall notices. Give both attached neighbours two months' notice for shared-wall work.
- Pin the price down. Price the agreed scheme, keeping a 6-9% contingency separate.
- Start on site. Sort the skip and parking bay permits, line up ULEZ-compliant deliveries and begin.
What Is the ROI of a Home Extension in Kennington?
In SE11 a sensible extension normally returns more than it costs. Research from Nationwide suggests 10% more floor space raises value by about 5%, and an extra bathroom by around 6%. Set that 5% against an £860,000 Kennington terrace and it is worth roughly £43,000, and a lower-ground or family scheme goes further still.
Kennington commands strong prices for its Georgian streets and central position. The ONS put the Lambeth average near £545,000 in 2026, with SE11 terraces well above that. The chart applies Nationwide uplift figures to an £860,000 Kennington terrace.
Values: ONS UK House Price Index, 2026. Uplift rates: Nationwide research. Actual uplift depends on the street ceiling price.
Every street has a ceiling price. A scheme that pushes a house well past what buyers pay on that road is unlikely to return its full cost. For wider context, read what adds the most value to a London home.
Is It Cheaper to Extend or Move in SE11?
For most Kennington owners, extending costs less than trading up once moving costs are counted. Moving from an £860,000 terrace to a £1,120,000 home means about £55,500 in Stamp Duty Land Tax alone under current GOV.UK rates, money that buys no extra space. A single-storey extension at £57,000 to £116,000 gives you the room and you keep it.
The stamp duty figure follows the standard residential bands published on GOV.UK, before conveyancing, agents and removals are even added. Build instead and you keep Kennington Park, the Oval and the Northern line that make SE11 so central.
Which Home Extension Designs Suit Kennington Homes?
The best Kennington extensions leave the Georgian front untouched and put the new space at the rear or below. A restrained rear addition in matching stock brick, a lower-ground lightwell and restored sashes suit the terraces, and on a Duchy lease the estate expects that same discipline in the detailing.
Good home extension design in SE11 is about discretion at the front and generosity at the back. Because the street elevation is protected, the value comes from a bright, well-planned rear and lower-ground, so rooflights, a lightwell and a glazed garden wall carry the daylight the front cannot be altered to provide.
In conservation areas, and under a Duchy lease, new work is expected to read as secondary to the historic house. Matching brick, retained joinery and reversible detailing tend to win consent. See our Kennington home extension service for the project types we build.
Kennington Home Extension Terms Explained
- Licence to alter
- The Duchy of Cornwall's permission to change a leasehold home, needed alongside planning on its estate.
- Duchy of Cornwall estate
- The large landholding around Kennington, including Courtenay Square and Cardigan Street, held on long leases.
- Listed building consent
- The extra approval a listed building needs before it can be altered, on top of or in place of planning.
- Lower-ground remodel
- Opening up or reworking a basement or semi-basement floor, usually lit by a lightwell.
- Lawful development certificate
- The certificate the council issues to confirm work was permitted development and needed no application.
- Party wall award
- The document two surveyors settle to control building work against a neighbour's wall.
- Build-over agreement
- Thames Water's sign-off for building within 3 metres of a public sewer.
How Do You Choose a Trusted Home Extension Builder in SE11?
Pick a firm that surveys before it prices, has carried a Duchy licence-to-alter and a Lambeth application through together, and commits to a fixed written figure. Membership of a body like the Federation of Master Builders is worth checking. Ask for proof of insurance, earlier building control sign-offs and the warranty on offer, and expect any Duchy lease or listed status raised at day one.
Buildaway is a registered FMB member. We provide a fixed written quotation once the survey is complete, backed by an 18-month workmanship warranty. See how we deliver home extensions across London.
Frequently Asked Questions
Can I build a rear extension without planning permission in Kennington?
Sometimes for a house, but Kennington is heavily conservation area and much of it is Duchy of Cornwall leasehold. Permitted development can allow a 3-metre rear extension on a terrace outside those controls, but flats have no such rights, listed houses need listed building consent, and a Duchy lease needs a licence to alter. Full planning plus an estate licence is the common route, so always take a lawful development certificate where PD applies.
How much does a single-storey rear extension cost in SE11 Kennington?
A single-storey rear extension in Kennington costs £57,000 to £116,000 in 2026 on Buildaway's quoting bands, roughly £2,700 to £3,700 per square metre. Georgian detailing and, on a Duchy lease, the licence-to-alter process add to the total. For a line-by-line breakdown see our Kennington extension cost guide, and allow £6,000 to £18,000 more for fees.
Does the Duchy of Cornwall need to approve my Kennington extension?
If your home is a Duchy leasehold, yes. The Duchy of Cornwall owns a large Kennington estate, including Courtenay Square, Cardigan Street and parts of Kennington Road and Lane, and its leases require a licence to alter before structural work. This runs alongside planning, not instead of it. The practical trick is to submit the Lambeth application and the Duchy licence from the same drawings within a fortnight, so they proceed in parallel rather than queueing.
How long does Lambeth take to decide a householder planning application?
The statutory period is eight weeks from validation. A Kennington conservation-area scheme needs a heritage statement, and a listed house adds listed building consent, both of which can extend it. On a Duchy lease, allow for the estate licence in parallel; queued rather than parallel, it can add roughly two months to the programme.
Is Kennington inside the Congestion Charge and ULEZ zones?
The whole of Kennington is inside the ULEZ, and the northern edge toward Elephant and Waterloo touches the Congestion Charge zone, so delivery and plant vehicles can pay both. Buildaway runs ULEZ-compliant vehicles as standard and factors any Congestion Charge into the programme, so on most SE11 jobs this is a minor line.
Do I need a party wall agreement for a terrace extension in Kennington?
Almost always. Kennington's Georgian and early Victorian terraces share walls on both sides, so a rear extension usually means notices to two adjoining owners. You must serve notice two months before party wall work and one month before excavating near a neighbour's foundations. Budget £2,200 to £6,000 per adjoining owner.
The Bottom Line on a Home Extension in Kennington
A Kennington extension is a consent exercise as much as a build. Between the conservation areas, the odd listed house and the Duchy of Cornwall estate, the paperwork decides the programme, and the single biggest lever is running planning and any Duchy licence together from one set of drawings. Sort the tenure and heritage first, and a Georgian terrace gains a bright rear and lower-ground without disturbing the street.
Work in order: survey, constraints, design, consent, then build. That keeps your home extension timeline honest and protects your home extension ROI. When you are ready, book a free site visit and fixed written quote with Buildaway.
By Cormac Hegarty, Director & Founder - Buildaway. Cormac Hegarty is the Founder of Buildaway and a residential construction specialist with a deep portfolio of projects across London.