Move
Total: £209,955
- SDLT (HMRC)
- £154,950
- Estate-agent fee
- £18,855
- Survey
- £1,500
- Legal (sale + purchase)
- £2,500
- Removals
- £2,000
- Chain contingency (1.5%)
- £30,150
Kensington and Chelsea: is it cheaper to extend or move in 2026?
For homeowners in Kensington and Chelsea (Royal Borough of Kensington and Chelsea). Updated 2026-06-11.
Inner west London. Georgian, early-Victorian and late-Victorian stucco-fronted terrace and villa stock — the most architecturally restricted residential area in the UK. Extensive listed buildings. Side returns rare and almost always require full planning; loft conversions in conservation areas typically require planning permission and heritage-led design.
The borough covers the SW1X, SW3, SW5, SW7, SW10, W2, W8, W10, W11, W14 postcode districts. Terraced homes here trade around £3,250,000 against the borough-wide £1,257,000 average.
In short
In Kensington and Chelsea, the average home is valued at £1,257,000. Moving up by 60% to a £2,010,000 property triggers approximately £154,950 in Stamp Duty Land Tax (SDLT). By contrast, a 22 m² high-spec rear extension (single storey) here costs around £144,716 all-in. Kensington and Chelsea has a borough-wide Article 4 direction removing permitted development rights for basements.
Your numbers
Adjust the inputs to see your scenario. The page updates instantly as you adjust the inputs.
Your result
Extending saves you £65,239
Extend
Rear extension (single storey) — high spec
Total: £144,716
- Build cost (22 m² × £4,400/m²)
- £96,800
- Professional fees (15%)
- £14,520
- Subtotal
- £111,320
- VAT (20%)
- £22,264
- Contingency (10%)
- £11,132
An extension of this type and size could add roughly £163,410 (≈13%) to your home's value — Nationwide Building Society, October 2025.
Your tipping line
Where moving starts costing more than the extension you selected. The chart follows your inputs above.
Up to about £1,527,000 of target price, moving is the cheaper route in Kensington and Chelsea; beyond that line, extending wins.
Extending in Kensington and Chelsea: what's different here
Local planning picture
- Conservation areas
- 38
- Householder decisions within 8 weeks
- 58%
- Build-cost tier
- prime central London
- Typical housing stock
- Victorian and Edwardian terraces
Decision speed: MHCLG householder statistics, year ending September 2025, excluding agreed extensions of time.
Worth knowing in Kensington and Chelsea
- Kensington and Chelsea has a borough-wide Article 4 direction removing permitted development rights for basements.
- The average home here is around £1,257,000 (ONS, 2026).
- Extension types suited to Victorian and Edwardian terraces: Rear extension (single storey), Kitchen extension, Loft conversion (mansard), Side return extension, Basement / lower-ground conversion.
How the £154,950 stamp duty stacks up
HMRC bands applied to a £2,010,000 purchase — the default Kensington and Chelsea trade-up.
| Price band | Rate | SDLT due |
|---|---|---|
| £0 – £125,000 | 0% | £0 |
| £125,000 – £250,000 | 2% | £2,500 |
| £250,000 – £925,000 | 5% | £33,750 |
| £925,000 – £1,500,000 | 10% | £57,500 |
| Above £1,500,000 | 12% | £61,200 |
What each suitable type costs vs the £209,955 move
High specification at typical size, prime central London rates, all-in.
| Extension type | All-in cost | vs moving |
|---|---|---|
| Rear extension (single storey) (22 m²) | £144,716 | saves £65,239 vs moving |
| Kitchen extension (22 m²) | £144,716 | saves £65,239 vs moving |
| Loft conversion (mansard) (30 m²) | £116,610 | saves £93,345 vs moving |
| Side return extension (12 m²) | £93,288 | saves £116,667 vs moving |
| Basement / lower-ground conversion (40 m²) | £418,600 | £208,645 more than moving |
Why this comparison matters
"Homeowners that add a loft conversion or extension, incorporating a large double bedroom and bathroom, can add as much as 24% to the value of a three-bedroom, one-bathroom house."
Frequently asked questions
- Is it cheaper to extend or move in Kensington and Chelsea?
- At Kensington and Chelsea's average £1,257,000 home moving up to £2,010,000, the move costs about £209,955 — including £154,950 of HMRC Stamp Duty. A 22 m² high-spec rear extension (single storey) runs roughly £144,716 at prime central London rates. Extending is cheaper here by about £65,239. Your real figure depends on extension size, specification and planning constraints.
- How much does an extension cost in Kensington and Chelsea in 2026?
- Budget around £145,000 all-in for a high-spec 22 m² rear extension (single storey) here — prime central London build rates run near £4,400/m². For a 22 m² kitchen extension expect roughly £145,000. Those totals already carry 15% professional fees, 20% VAT and a 10% contingency; access, specification and ground conditions move the final number.
- How long does planning permission take in Kensington and Chelsea?
- The statutory determination period for a householder application is 8 weeks. Royal Borough of Kensington and Chelsea decided 58% of householder applications within 8 weeks in the year to September 2025 (MHCLG figures, excluding agreed extensions of time). Industry-compiled figures suggest around 92% of applications here are approved, though that is not an official statistic. A householder application costs £548 from April 2026, and a Larger Home Extension prior approval £240.
- Do I need planning permission for an extension in Kensington and Chelsea?
- Many single-storey rear extensions fall under Permitted Development — no planning permission needed. Kensington and Chelsea has the most restrictive planning regime in London. The borough is almost entirely covered by conservation areas, with Article 4 directions removing PD rights for most external alterations. Listed buildings are also extensive. Assume full planning permission required for almost any external work; PD route exceptional. Kensington and Chelsea has 38 conservation areas, including Chelsea, Royal Hospital, Holland Park, where PD rights are curtailed. Side extensions, large rear extensions and most wraparounds need full planning regardless. Check the Royal Borough of Kensington and Chelsea planning portal first. Open the Royal Borough of Kensington and Chelsea planning portal
- How long does a rear extension (single storey) take in Kensington and Chelsea?
- Allow around 16 weeks on site for a typical rear extension (single storey) in Kensington and Chelsea, after design, party wall agreements with neighbours and the council's determination period. A kitchen extension runs nearer 14 weeks. End to end, plan 4–8 months from first call to completion — longer in conservation areas or where structural surveys are needed.
- How much value does an extension add in Kensington and Chelsea?
- On a £1,257,000 Kensington and Chelsea home, the uplift is roughly £163,400 to £301,700: Nationwide Building Society (October 2025) put an extra double bedroom at about 13% of value, and a full loft conversion plus extension at up to 24%. The realised return depends on your street's ceiling price, buyer demand in Kensington and Chelsea and the specification you choose.
- Can I live in my home during the extension build?
- In Kensington and Chelsea's period stock, staying put depends on the project: a rear or kitchen extension is usually liveable with 2–3 weeks of real disruption, while mansard lofts and basements are far more invasive — basements in particular can mean months of structural works. Many Kensington and Chelsea owners decant for the heaviest phase and budget accordingly.
- Can I build a basement in Kensington and Chelsea?
- Yes, but not under permitted development: Royal Borough of Kensington and Chelsea has a borough-wide Article 4 direction removing PD rights for basement development, so every basement needs a full planning application. Local policy limits most schemes to a single storey and around 50% of the garden, with engineer-certified method statements required. Budget prime central London basement rates and 6–12 months of works.
- At what price does moving stop making sense in Kensington and Chelsea?
- Starting from Kensington and Chelsea's average £1,257,000 home with a 22 m² high-spec rear extension (single storey) (£144,716 all-in), the tipping line sits at roughly £1,527,000: buying above that price costs more in SDLT and moving fees than the extension itself. Below it, moving stays the cheaper route. The live chart on this page recalculates the line for your own inputs.
- How much stamp duty would I pay moving up in Kensington and Chelsea?
- On a typical Kensington and Chelsea trade-up from £1,257,000 to £2,010,000 (a 60% step up), Stamp Duty Land Tax (SDLT) is £154,950 — an effective rate of 7.71%. First-time buyers and additional-property buyers pay different rates. Use HMRC's official calculator at tax.service.gov.uk for your exact figure. HMRC Stamp Duty calculator
Compare nearby London boroughs
Nearby by average property value — useful if you're weighing a move to an adjacent price tier. A comparable trade-up in Camden would carry about £90,750 of stamp duty — £64,200 less than in Kensington and Chelsea.
Methodology and sources
Stamp Duty Land Tax is calculated from the HMRC bands in force for the 2025–26 tax year. Verify any figure against HMRC's official calculator before committing. Extension costs use prime central London £/m² rates by extension type — industry-estimate midpoints, presented as approximations.
- GOV.UK Stamp Duty Land Tax guidance — gov.uk/stamp-duty-land-tax
- Nationwide House Price Index (October 2025 release) — value-add commentary attributed to Andrew Harvey, Senior Economist.
- HM Land Registry / ONS UK House Price Index — borough average property values (March 2026 release).
- MHCLG planning statistics (PS2 dashboard) — householder decision speed, year ending September 2025.
- London 2026 £/m² grid by extension type and tier — Build Team benchmark compiled from BCIS/RICS, FMB and published architect guides (refreshed quarterly).
- Conservation-area counts and Article 4 status — individual London borough councils, verified 2026.
- HMRC SDLT calculator — tax.service.gov.uk/calculate-stamp-duty-land-tax