BOROUGH · PROJECT

Rear extension in Bexley

Planning permission, real costs and what actually gets approved

Do you need planning permission for a rear extension in Bexley?

Outside the conservation areas, much of Bexley's suburban semi-detached stock keeps permitted development rights for a single-storey rear extension within the limits, or larger via prior approval. Inside a conservation area, a full application is needed. The borough-wide small-HMO conversion direction (since 24 September 2017) does not itself remove ordinary rear-extension rights.

Bexleyheath, Sidcup and Erith semis extend routinely under PD; Old Bexley and the conservation areas need a full application.

Bexley runs from Bexleyheath and Sidcup to older village cores and the Thames-side at Erith. Generous interwar plots with side access make rear extensions a staple outside protected streets. Conservation areas concentrate design scrutiny on historic and best-designed streets rather than blanketing the whole borough.

CHECK

What actually applies in Bexley

Conservation areas in Bexley

Real · planning.data.gov.uk

Every designated conservation area in Bexley from the official dataset — inside one, permitted development narrows and design scrutiny rises.

  • Brook Street
  • Christ Church
  • Crossness
  • Erith Riverside
  • Erith Road
  • Foots Cray
  • Halfway Street
  • High Beeches
  • Iron Mill Lane
  • Lesney Park Road
  • Longlands Road
  • North Cray Village
  • Oak Road
  • Old Bexley
  • Old Forge Way
  • Parkhurst
  • Red House Lane
  • Star Hill
  • The Green
  • The Hollies
  • The Oval
  • Willersley Avenue and Braundton Avenue
  • Woolwich Road

…plus 8 further designated areas.

Source: planning.data.gov.uk · Open Government Licence. Boundaries are checked at address level by the area report.

Article 4 directions in Bexley

Real · planning.data.gov.uk

No Article 4 geometry for Bexley appears in the national planning.data.gov.uk dataset, but the borough has operated a borough-wide HMO Article 4 direction since 24 September 2017, removing the right to convert a house to a small HMO (three to six occupants), plus householder directions in its conservation areas. 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.

Average house price
£413,126
Annual change
+2.0%

Prices: HM Land Registry UK House Price Index, December 2025 · Open Government Licence.

How often Bexley grants householder applications: 95.3% of householder applications decided were granted (895 of 939) over 2025 Q2 to 2026 Q1 — rank 31 of 33 for lowest grant rate. London average: 85.6%. Householder applications are the class most rear extensions fall under. See the full householder approval-rate league table →
ROUTE

The planning route — PD or permission?

Permitted development (GPDO Class A) covers single-storey rear extensions up to 3m beyond the original rear wall on attached houses and 4m on detached, with a maximum height of 4m. The 'larger home extension' route extends this to 6m/8m through prior approval with neighbour consultation — but that larger route is not available in conservation areas.

In conservation areas, the basic 3m/4m single-storey rear PD allowance usually survives — what conservation-area status removes is side extensions and two-storey rear extensions. An Article 4 direction can remove more, but Camden's directions in Hampstead and Belsize target front-and-side appearance (solar panels, window changes, boundary treatments), not the single-storey rear allowance. Flats have no PD rights at all. Two-storey rear extensions in conservation areas always need full permission.

Practical rule across London: check the address first. If a conservation area or Article 4 direction applies, budget for a full householder application decided on design, neighbour daylight (the 45-degree test) and materials.

LIMITS

Permitted development limits — rear extension

Single-storey rear depth — attached house3m beyond the original rear wall
Single-storey rear depth — detached house4m beyond the original rear wall
Larger extension via prior approval6m attached / 8m detached — not in conservation areas
Maximum height (single storey)4m
Two-storey rear in a conservation areaFull planning permission required
FlatsNo permitted development rights

Limits summarise the General Permitted Development Order (Schedule 2, Part 1) as it applies in London. In Bexley, 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.

COST

How much does a rear extension cost in Bexley?

Cost per m² (low — straightforward site)£3,000
Cost per m² (expected)£3,800
Cost per m² (high — conservation spec, hard access)£4,600+
Typical build cost (12–18m² single storey)£36,000 – £83,000
Professional fees, surveys, party wall (add)10–18% of build

Indicative London ranges calibrated from real project data. Conservation-area specifications (matching stock brick, lime mortar, bespoke glazing) and restricted rear access are the two biggest cost drivers. VAT not included.

TIME

Realistic timeline

Design and drawings4–8 weeks
Planning decision (full application)8–12 weeks (8-week statutory target)
Prior approval route, where available42 days
Party wall agreements4–10 weeks (parallel)
Build3–5 months
WATCH

What catches people out in Bexley

National geometry does not currently hold Bexley's Article 4 directions — confirm HMO and conservation-area positions on the council's pages. Daylight and party wall issues remain routine hold-ups.

DISTRICTS

Postcode districts in Bexley

DA5 — Bexley & Old Bexley

DA5 is Old Bexley — the historic village conservation area on the Cray, with Hall Place nearby and North Cray Village beyond.

DA5 — Bexley & Old Bexley →
DA6 — Bexleyheath

DA6 is Bexleyheath — the suburban town centre and the streets towards Danson Park.

DA6 — Bexleyheath →
DA7 — Barnehurst & Bexleyheath

DA7 covers Barnehurst and northern Bexleyheath, near the Red House Lane conservation area around William Morris's Red House.

DA7 — Barnehurst & Bexleyheath →
DA8 — Erith

DA8 is Erith — the Erith Riverside and Erith Road conservation areas on the Thames.

DA8 — Erith →
DA15 — Sidcup

DA15 covers Sidcup and Lamorbey, including the Halfway Street conservation area.

DA15 — Sidcup →
DA14 — Sidcup & Foots Cray

DA14 covers Sidcup and Foots Cray in Bexley — suburban semis and older village cores.

DA14 — Sidcup & Foots Cray →
DA16 — Welling & East Wickham

DA16 is Welling and East Wickham — interwar Bexley stock with a Greenwich edge.

DA16 — Welling & East Wickham →
DA17 — Belvedere & Erith fringe

DA17 covers Belvedere and the Erith fringe in Bexley.

DA17 — Belvedere & Erith fringe →
DA18 — Erith & Thamesmead East

DA18 is Erith and Thamesmead East in Bexley — a mix of riverside regeneration, later estate stock and suburban streets.

DA18 — Erith & Thamesmead East →
FAQ

Rear extension in Bexley, asked straight

01

Do I need planning permission for a rear extension in Bexley?

Outside conservation areas, many houses can use permitted development or prior approval. Inside a conservation area, expect a full application.
02

How much does a rear extension cost in Bexley?

Budget £3,000–£4,600+ per m², or roughly £36,000–£83,000 for a typical 12–18m² single-storey scheme, before VAT and 10–18% fees.
03

Does the September 2017 small-HMO conversion direction affect rear extensions?

No — that direction requires permission to convert a house to a small HMO. It does not itself remove ordinary rear-extension permitted development on unconstrained houses.
04

Is Green Belt a major factor?

Less of a defining householder filter than in some outer boroughs — conservation designation and ordinary PD limits matter more for most suburban extensions. Still check the address.
05

Do I need a party wall agreement?

Almost always on terraced and semi-detached houses when foundations or the structure affect a shared wall.
CHECK

What applies at your address?

Borough-level rules only narrow it down. Enter a Bexley postcode for the live constraint check — conservation area, Article 4 and sold-price comparables, cited to source.

Check a Bexley address

Need it in writing for one address? A planning permission report for a Bexley 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.

Check an address