Move
Total: £92,800
- SDLT (HMRC)
- £58,750
- Estate-agent fee
- £10,800
- Survey
- £1,500
- Legal (sale + purchase)
- £2,500
- Removals
- £2,000
- Chain contingency (1.5%)
- £17,250
Move or extend in Islington? 2026 cost comparison
For homeowners in Islington (London Borough of Islington). Updated 2026-06-11.
Inner north London. Predominantly Georgian and Victorian terrace stock — Islington has one of the highest densities of Grade II-listed period property in any London borough. Side return geometry common but the planning route is almost always full planning given Article 4 coverage. Loft conversions in conservation areas usually require planning permission.
The borough covers the EC1A, EC1N, EC1R, EC1V, N1, N4, N5, N7, N19 postcode districts. Terraced homes here trade around £1,075,000 against the borough-wide £720,000 average.
In short
In Islington, the average home is valued at £720,000. Moving up by 60% to a £1,150,000 property triggers approximately £58,750 in Stamp Duty Land Tax (SDLT). By contrast, a 12 m² high-spec side return extension here costs around £82,524 all-in. Only 41% of householder planning applications here are decided within 8 weeks — among the slowest in London.
Your numbers
Adjust the inputs to see your scenario. The page updates instantly as you adjust the inputs.
Your result
Extending saves you £10,276
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 £93,600 (≈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 £1,065,000 of target price, moving is the cheaper route in Islington; beyond that line, extending wins.
Extending in Islington: what's different here
Local planning picture
- Conservation areas
- 41
- Householder decisions within 8 weeks
- 41%
- 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 Islington
- Only 41% of householder planning applications here are decided within 8 weeks — among the slowest in London.
- The average home here is around £720,000 (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 £58,750 stamp duty stacks up
HMRC bands applied to a £1,150,000 purchase — the default Islington 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% | £22,500 |
What each suitable type costs vs the £92,800 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 | saves £10,276 vs moving |
| Rear extension (single storey) (22 m²) | £124,982 | £32,182 more than moving |
| Wrap-around extension (25 m²) | £108,388 | £15,588 more than moving |
| Kitchen extension (22 m²) | £124,982 | £32,182 more than moving |
| Loft conversion (dormer) (18 m²) | £47,093 | saves £45,707 vs moving |
| Loft conversion (mansard) (30 m²) | £103,155 | £10,355 more than moving |
Why this comparison matters
"Authorities granted 90% of these applications and decided 93% within eight weeks or the agreed time."
Frequently asked questions
- Is it cheaper to extend or move in Islington?
- At Islington's average £720,000 home moving up to £1,150,000, the move costs about £92,800 — including £58,750 of HMRC Stamp Duty. A 12 m² high-spec side return extension runs roughly £82,524 at inner London rates. Extending is cheaper here by about £10,276. Your real figure depends on extension size, specification and planning constraints.
- Can I live in my home during the extension build?
- Most Islington 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 Islington?
- Starting from Islington's average £720,000 home with a 12 m² high-spec side return extension (£82,524 all-in), the tipping line sits at roughly £1,065,000: 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 Islington?
- On a typical Islington trade-up from £720,000 to £1,150,000 (a 60% step up), Stamp Duty Land Tax (SDLT) is £58,750 — an effective rate of 5.11%. 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 Islington in 2026?
- A 12 m² side return extension in Islington 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.
- How long does planning permission take in Islington?
- The statutory determination period for a householder application is 8 weeks. London Borough of Islington decided 41% of householder applications within 8 weeks in the year to September 2025 (MHCLG figures, excluding agreed extensions of time) — among the slowest 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 Islington?
- Many single-storey rear extensions fall under Permitted Development — no planning permission needed. Islington operates extensive Article 4 directions. A borough-wide Article 4 removes PD rights for change of use C3-to-C4 (HMO). Multiple zone-specific Article 4 directions remove PD rights for side and rear extensions and roof alterations in named conservation areas. Effect: most external alterations on Islington's classic Georgian and Victorian terraces require full planning permission. Islington has 41 conservation areas, including Barnsbury, Canonbury, Tufnell Park, where PD rights are curtailed. Side extensions, large rear extensions and most wraparounds need full planning regardless. Check the London Borough of Islington planning portal first. Open the London Borough of Islington planning portal
- How long does a side return extension take in Islington?
- Allow around 16 weeks on site for a typical side return extension in Islington, 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 Islington 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 Islington average of £720,000, that's roughly £93,600 to £172,800 of capital uplift. Final return depends on the local market, the type of buyer in Islington, 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 Wandsworth would carry about £53,250 of stamp duty — £5,500 less than in Islington.
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.
- 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
- 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).