Move
Total: £48,825
- SDLT (HMRC)
- £25,500
- Estate-agent fee
- £6,675
- Survey
- £1,500
- Legal (sale + purchase)
- £2,500
- Removals
- £2,000
- Chain contingency (1.5%)
- £10,650
Stamp duty vs extension costs in Sutton — 2026 guide
For homeowners in Sutton (London Borough of Sutton). Updated 2026-06-11.
Outer south London. Predominantly 1930s suburban semi-detached and postwar housing, with pockets of older village stock (Carshalton, Cheam, Wallington). Loft and rear extensions dominate; side returns rare on suburban semis.
The borough covers the CR4, SM1, SM2, SM3, SM4, SM5, SM6, SM7 postcode districts. Terraced homes here trade around £465,000 against the borough-wide £445,000 average.
In short
In Sutton, the average home is valued at £445,000. Moving up by 60% to a £710,000 property triggers approximately £25,500 in Stamp Duty Land Tax (SDLT). By contrast, a 22 m² high-spec rear extension (single storey) here costs around £108,537 all-in. 90% of householder applications here are decided within 8 weeks — among the fastest in London.
Your numbers
Adjust the inputs to see your scenario. The page updates instantly as you adjust the inputs.
Your result
Moving is £59,712 cheaper than extending
Extend
Rear extension (single storey) — high spec
Total: £108,537
- Build cost (22 m² × £3,300/m²)
- £72,600
- Professional fees (15%)
- £10,890
- Subtotal
- £83,490
- VAT (20%)
- £16,698
- Contingency (10%)
- £8,349
An extension of this type and size could add roughly £57,850 (≈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 £1,325,000 of target price, moving is the cheaper route in Sutton; beyond that line, extending wins.
Extending in Sutton: what's different here
Local planning picture
- Conservation areas
- 15
- Householder decisions within 8 weeks
- 90%
- Build-cost tier
- outer London
- Typical housing stock
- 1930s semi-detached homes
Decision speed: MHCLG householder statistics, year ending September 2025, excluding agreed extensions of time.
Worth knowing in Sutton
- 90% of householder applications here are decided within 8 weeks — among the fastest in London.
- The average home here is around £445,000 (ONS, 2026).
- Extension types suited to 1930s semi-detached homes: Rear extension (single storey), Rear extension (double storey), Two-storey side extension, Garage conversion, Loft conversion (hip-to-gable), Over-garage extension.
How the £25,500 stamp duty stacks up
HMRC bands applied to a £710,000 purchase — the default Sutton trade-up.
| Price band | Rate | SDLT due |
|---|---|---|
| £0 – £125,000 | 0% | £0 |
| £125,000 – £250,000 | 2% | £2,500 |
| £250,000 – £925,000 | 5% | £23,000 |
What each suitable type costs vs the £48,825 move
High specification at typical size, outer London rates, all-in.
| Extension type | All-in cost | vs moving |
|---|---|---|
| Rear extension (single storey) (22 m²) | £108,537 | £59,712 more than moving |
| Rear extension (double storey) (45 m²) | £208,553 | £159,728 more than moving |
| Two-storey side extension (35 m²) | £167,440 | £118,615 more than moving |
| Garage conversion (18 m²) | £43,056 | saves £5,769 vs moving |
| Loft conversion (hip-to-gable) (25 m²) | £67,275 | £18,450 more than moving |
| Over-garage extension (18 m²) | £34,983 | saves £13,842 vs moving |
Why this comparison matters
"An architect-designed house extension in London may cost between £3,000 and £5,000 per square metre. Elsewhere in the UK, you can expect to pay between £2,000 and £3,500 per square metre."
Frequently asked questions
- Is it cheaper to extend or move in Sutton?
- At Sutton's average £445,000 home moving up to £710,000, the move costs about £48,825 — including £25,500 of HMRC Stamp Duty. A 22 m² high-spec rear extension (single storey) runs roughly £108,537 at outer London rates. Moving is cheaper here by about £59,712. Your real figure depends on extension size, specification and planning constraints.
- Can I live in my home during the extension build?
- Most Sutton families stay in their home during a rear extension or garage conversion — works are contained to one side of the house. Two-storey side extensions and hip-to-gable lofts are noisier: expect 4–6 weeks where one floor or the driveway side is out of action. Plan temporary kitchen arrangements and dust control for the noisy weeks.
- At what price does moving stop making sense in Sutton?
- Starting from Sutton's average £445,000 home with a 22 m² high-spec rear extension (single storey) (£108,537 all-in), the tipping line sits at roughly £1,325,000: 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 Sutton?
- On a typical Sutton trade-up from £445,000 to £710,000 (a 60% step up), Stamp Duty Land Tax (SDLT) is £25,500 — an effective rate of 3.59%. 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
- What does a typical extension cost in Sutton in 2026?
- A 22 m² rear extension (single storey) in Sutton runs about £109,000 all-in at high specification, on outer London build rates of around £3,300/m². A 45 m² rear extension (double storey) comes to roughly £209,000. All-in figures include 15% professional fees, 20% VAT and a 10% contingency — final cost depends on access, specification and ground conditions.
- How long does planning permission take in Sutton?
- The statutory determination period for a householder application is 8 weeks. London Borough of Sutton decided 90% of householder applications within 8 weeks in the year to September 2025 (MHCLG figures, excluding agreed extensions of time) — among the fastest in London. Across London, authorities grant roughly low-to-mid 80s per cent of applications. 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 Sutton?
- Many single-storey rear extensions fall under Permitted Development — no planning permission needed. Sutton has a limited Article 4 footprint, mainly affecting named conservation areas. Householder extensions outside conservation areas typically retain PD rights. Sutton has 15 conservation areas, including Sutton Town Centre, Carshalton Village, Carshalton Beeches, where PD rights are curtailed. Side extensions, large rear extensions and most wraparounds need full planning regardless. Check the London Borough of Sutton planning portal first. Open the London Borough of Sutton planning portal
- How long does a rear extension (single storey) take in Sutton?
- Allow around 16 weeks on site for a typical rear extension (single storey) in Sutton, after design, party wall agreements with neighbours and the council's determination period. A rear extension (double storey) runs nearer 20 weeks. End to end, plan 4–8 months from first call to completion — longer in conservation areas or where structural surveys are needed.
- Will an extension add value to my Sutton home?
- Nationwide Building Society (October 2025) found that adding a double bedroom can lift a home's value by about 13%, and a full loft conversion plus extension by up to 24%. On a Sutton average of £445,000, that's roughly £57,900 to £106,800 of capital uplift. Final return depends on the local market, the type of buyer in Sutton, and your extension's specification.
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 Hillingdon would carry about £26,500 of stamp duty — £1,000 more than in Sutton.
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 outer London £/m² rates by extension type — industry-estimate midpoints, presented as approximations.
- HMRC SDLT calculator — tax.service.gov.uk/calculate-stamp-duty-land-tax
- 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.