Move
Total: £51,800
- SDLT (HMRC)
- £27,500
- Estate-agent fee
- £7,050
- Survey
- £1,500
- Legal (sale + purchase)
- £2,500
- Removals
- £2,000
- Chain contingency (1.5%)
- £11,250
Stamp duty vs extension costs in Greenwich — 2026 guide
For homeowners in Greenwich (Royal Borough of Greenwich). Updated 2026-06-11.
South-east London bordering the river. Georgian and Regency stock in West Greenwich and the WHS area; Victorian terrace in Greenwich, Charlton and Woolwich; interwar suburban semi-detached around Eltham and Well Hall (notably the Progress Estate). Side returns common in the western wards; loft and rear extensions dominate the suburban stock.
The borough covers the BR7, DA8, SE2, SE3, SE7, SE9, SE10, SE12, SE18, SE28 postcode districts. Terraced homes here trade around £525,000 against the borough-wide £470,000 average.
In short
In Greenwich, the average home is valued at £470,000. Moving up by 60% to a £750,000 property triggers approximately £27,500 in Stamp Duty Land Tax (SDLT). By contrast, a 12 m² high-spec side return extension here costs around £82,524 all-in. The average home here is around £470,000 (ONS, 2026).
Your numbers
Adjust the inputs to see your scenario. The page updates instantly as you adjust the inputs.
Your result
Moving is £30,724 cheaper than extending
Extend
Side return extension — high spec
Total: £82,524
- Build cost (12 m² × £4,600/m²)
- £55,200
- Professional fees (15%)
- £8,280
- Subtotal
- £63,480
- VAT (20%)
- £12,696
- Contingency (10%)
- £6,348
An extension of this type and size could add roughly £61,100 (≈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 £1,095,000 of target price, moving is the cheaper route in Greenwich; beyond that line, extending wins.
Extending in Greenwich: what's different here
Local planning picture
- Conservation areas
- 23
- Householder decisions within 8 weeks
- 78%
- Build-cost tier
- inner 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 Greenwich
- The average home here is around £470,000 (ONS, 2026).
- Extension types suited to Victorian and Edwardian terraces: Side return extension, Rear extension (single storey), Wrap-around extension, Kitchen extension, Loft conversion (dormer), Loft conversion (mansard).
How the £27,500 stamp duty stacks up
HMRC bands applied to a £750,000 purchase — the default Greenwich trade-up.
| Price band | Rate | SDLT due |
|---|---|---|
| £0 – £125,000 | 0% | £0 |
| £125,000 – £250,000 | 2% | £2,500 |
| £250,000 – £925,000 | 5% | £25,000 |
What each suitable type costs vs the £51,800 move
High specification at typical size, inner London rates, all-in.
| Extension type | All-in cost | vs moving |
|---|---|---|
| Side return extension (12 m²) | £82,524 | £30,724 more than moving |
| Rear extension (single storey) (22 m²) | £124,982 | £73,182 more than moving |
| Wrap-around extension (25 m²) | £108,388 | £56,588 more than moving |
| Kitchen extension (22 m²) | £124,982 | £73,182 more than moving |
| Loft conversion (dormer) (18 m²) | £47,093 | saves £4,707 vs moving |
| Loft conversion (mansard) (30 m²) | £103,155 | £51,355 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 Greenwich?
- At Greenwich's average £470,000 home moving up to £750,000, the move costs about £51,800 — including £27,500 of HMRC Stamp Duty. A 12 m² high-spec side return extension runs roughly £82,524 at inner London rates. Moving is cheaper here by about £30,724. Your real figure depends on extension size, specification and planning constraints.
- How long does planning permission take in Greenwich?
- The statutory determination period for a householder application is 8 weeks. Royal Borough of Greenwich decided 78% of householder applications within 8 weeks in the year to September 2025 (MHCLG figures, excluding agreed extensions of time). About 75% of applications here were granted (MHCLG, Q3 2025). 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 Greenwich?
- Many single-storey rear extensions fall under Permitted Development — no planning permission needed. Greenwich has Article 4 directions in conservation areas (notably West Greenwich and the Maritime Greenwich World Heritage Site buffer zone, where most external alterations require full planning) and an HMO Article 4. Greenwich has 23 conservation areas, including Maritime Greenwich (UNESCO WHS), West Greenwich, Blackheath, where PD rights are curtailed. Side extensions, large rear extensions and most wraparounds need full planning regardless. Check the Royal Borough of Greenwich planning portal first. Open the Royal Borough of Greenwich planning portal
- How long does a side return extension take in Greenwich?
- Allow around 16 weeks on site for a typical side return extension in Greenwich, after design, party wall agreements with neighbours and the council's determination period. A rear extension (single storey) runs nearer 16 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 Greenwich 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 Greenwich average of £470,000, that's roughly £61,100 to £112,800 of capital uplift. Final return depends on the local market, the type of buyer in Greenwich, and your extension's specification.
- Can I live in my home during the extension build?
- Most Greenwich families stay in their home during a single-storey rear or side return extension — the build is contained to the back, and your kitchen is typically rebuilt in 2–3 weeks of disruption. Loft conversions and full wraparounds are harder: expect 4–6 weeks where one floor is unusable. Plan for temporary kitchen arrangements and dust everywhere.
- At what price does moving stop making sense in Greenwich?
- Starting from Greenwich's average £470,000 home with a 12 m² high-spec side return extension (£82,524 all-in), the tipping line sits at roughly £1,095,000: 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 Greenwich?
- On a typical Greenwich trade-up from £470,000 to £750,000 (a 60% step up), Stamp Duty Land Tax (SDLT) is £27,500 — an effective rate of 3.67%. 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 Greenwich in 2026?
- A 12 m² side return extension in Greenwich runs about £83,000 all-in at high specification, on inner London build rates of around £4,600/m². A 22 m² rear extension (single storey) comes to roughly £125,000. All-in figures include 15% professional fees, 20% VAT and a 10% contingency — final cost depends on access, specification and ground conditions.
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 Enfield would carry about £27,250 of stamp duty — £250 less than in Greenwich.
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 inner London £/m² rates by extension type — industry-estimate midpoints, presented as approximations.
- 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
- GOV.UK Stamp Duty Land Tax guidance — gov.uk/stamp-duty-land-tax