Basement extension in Greenwich
Do you need planning permission for a basement extension in Greenwich?
Yes — expect a full application with structural evidence and, near the river, flood-risk evidence, under the Residential Extensions, Basements and Conversions SPD. There is no useful permitted-development route.
Covered by the Residential Extensions, Basements and Conversions SPD; expect a full application with structural and, near the river, flood-risk evidence.
The SPD explicitly covers basements as well as extensions and conversions, so the design and structural case has a written frame. Near the Thames, groundwater and flood risk are early feasibility filters. Conservation and listed stock add scrutiny of lightwells and other visible works.
What actually applies in Greenwich
Conservation areas in Greenwich
Real · planning.data.gov.uk14 designated areas are recorded in the official dataset for this borough without published names. The area report still checks an address against their real boundaries — see the council's own conservation-area and Article 4 pages for the named schedules.
Source: planning.data.gov.uk · Open Government Licence · 14 recorded.
Article 4 directions in Greenwich
Real · planning.data.gov.ukNo Article 4 geometry for Greenwich appears in the national planning.data.gov.uk dataset, but the Royal Borough operates householder Article 4 directions in a number of its conservation areas — among them the Ashburnham Triangle, West Greenwich, East Greenwich, the Rectory Field, the Shrewsbury Park Estate and the Progress Estate — removing permitted development rights so that visible external alterations need planning permission. The Residential Extensions, Basements and Conversions Guidance SPD sets the design rules. Check the council's Article 4 pages for the position at a specific address.
Source: planning.data.gov.uk · Open Government Licence. Checked at address level by the area report.
Prices: HM Land Registry UK House Price Index, December 2025 · Open Government Licence.
The planning route — PD or permission?
There is no useful permitted development route for basements in practice — assume a full planning application everywhere, with a Basement Impact Assessment covering ground conditions, hydrology, structural methodology and construction management. Camden, Westminster and Islington all limit basements to a single storey in most circumstances and protect listed buildings from excavation almost absolutely.
In a conservation area — which blankets much of prime north-west London, from Hampstead to St John's Wood — there is no permitted-development route to lose, but the visible elements are assessed closely on heritage grounds: lightwells, railings, front-garden changes, rooflights and any external alteration. An Article 4 direction or a listed building can remove the option of excavation altogether.
Party wall procedure is heavier than for any other project: underpinning shared walls triggers awards with detailed method statements on both sides, and neighbour objections — on noise, vibration, structural risk and years of disruption — are the norm rather than the exception. The applications that succeed arrive with the engineering done, not promised.
Permitted development limits — basement extension
| Permitted development | None in practice — assume a full planning application |
| Required technical evidence | Basement Impact Assessment (ground, hydrology, structure, construction management) |
| Depth, in most inner-London boroughs | Single storey in most circumstances |
| Listed buildings | Excavation protected against almost absolutely |
| Party wall procedure | Awards with method statements where underpinning shared walls |
Limits summarise the General Permitted Development Order (Schedule 2, Part 1) as it applies in London. In Greenwich, a conservation area, Article 4 direction or listed status changes the route — the panels above show what is designated, and the address check confirms what applies at your property.
How much does a basement extension cost in Greenwich?
| Cost per m² (low) | £6,000 |
| Cost per m² (expected) | £8,500 |
| Cost per m² (high — difficult ground / high water table) | £12,000+ |
| Typical project (35–50m² single storey) | £210,000 – £600,000 |
| Professional and consultant fees (add) | 15–25% of build |
Basements carry the widest cost uncertainty of any project — ground conditions and water management can move budgets six figures. Ranges from real project data; VAT excluded. Never commit on a single quote without a ground investigation.
Realistic timeline
| Feasibility, ground investigation, BIA | 3–6 months |
| Planning decision | 10–16 weeks |
| Party wall awards (multiple) | 3–6 months (parallel) |
| Build | 8–14 months |
What catches people out in Greenwich
Ground conditions near the river can end a scheme at feasibility or move the budget by six figures. Party wall and construction-management conditions still dominate programme on terrace sites.
Postcode districts in Greenwich
SE10 is the Maritime Greenwich World Heritage core — the Old Royal Naval College, Queen's House and Royal Observatory — wrapped by the West Greenwich, East Greenwich and Ashburnham Triangle conservation areas, several with Article 4 directions.
SE10 — Greenwich & Maritime Greenwich →SE3 covers the Blackheath and Westcombe Park conservation areas around the heath (Blackheath is shared with Lewisham).
SE3 — Blackheath & Westcombe Park →SE7 is Charlton — the Charlton Village conservation area around Charlton House and the Rectory Field, which carries an Article 4 direction.
SE7 — Charlton →SE9 is Eltham — home to the Progress Estate, a celebrated First World War garden suburb with an Article 4 direction, and Eltham Palace nearby.
SE9 — Eltham →SE18 covers Woolwich, the Royal Arsenal riverside and the Shrewsbury Park Estate conservation area (which carries an Article 4 direction) above Plumstead.
SE18 — Woolwich & Plumstead →SE2 covers Abbey Wood and the Thamesmead fringe, mainly in Greenwich with a Bexley edge.
SE2 — Abbey Wood & Thamesmead fringe →SE28 is Thamesmead — later twentieth-century stock and estate layouts in Greenwich (with a Bexley edge), different from the Victorian terrace belts further west.
SE28 — Thamesmead →Basement extension in Greenwich, asked straight
Do basements need planning permission in Greenwich?
How much does a basement cost?
Is a basement harder near the river?
Does listed status stop a basement?
What is the biggest risk?
What applies at your address?
Borough-level rules only narrow it down. Enter a Greenwich postcode for the live constraint check — conservation area, Article 4 and sold-price comparables, cited to source.
Need it in writing for one address? A planning permission report for a Greenwich property — from £59, or surveyor-reviewed from £295.
Planning Permission Checker provides planning and cost intelligence for early feasibility only. It is not legal, planning, valuation, architectural, structural, or surveying advice. All estimates are indicative and must be verified by qualified professionals before purchase, design, planning submission, or construction.
Cost estimates are indicative only — not a quotation. Final price depends on survey, specification, structure, access, party wall matters, VAT, professional fees, and contractor availability.
Planning outcomes are not guaranteed. Local planning authorities make final decisions.