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Permitted Development Extensions in the UK

Maximum extension sizes without planning permission. A checklist of what to verify, where rules differ across the four UK nations, and official sources. The Dashboard's AI Objection Risk Analyzer can help screen a specific property.

A row of traditional Georgian-style terraced houses with brick facades and white window surrounds under a blue sky
Georgian-style terraced housing, illustrative of UK residential architecture. Image is illustrative, not location-specific.Photo via Unsplash

Reviewed by the Scapely editorial team on 23 October 2026

Where this strategy is England-only

The householder and other permitted development allowances people quote online come from the English General Permitted Development Order. Wales, Scotland and Northern Ireland each have their own, different order and limits, so English size limits must not be used here.

Council pages for Wales, Scotland and Northern Ireland explain the alternative route for each nation.

What to verify

  1. Confirm the house still has its permitted development rights (not flats, not previously used up, no Article 4 direction).
  2. Measure against the current rules for the nation you are in; do not reuse English limits elsewhere.
  3. Check conservation area, listed status and Article 4 restrictions on the address.
  4. Consider a lawful development certificate to prove the position.
  5. Check neighbour consultation and prior approval requirements for larger extensions.

Building safety triggers

In England, higher-risk building rules generally apply to buildings of at least 18 metres or 7 storeys that contain at least two homes (and to some care homes and hospitals). Which gateway steps apply depends on the building's height, storeys and use and on the proposed work. It is not set by the council.

GOV.UK guidance on higher-risk buildings

Permitted Development Extensions by council

Viability of permitted Development Extensions depends on the exact address: local policy, designations such as Article 4 areas, and build cost. See council-specific checklists below:

Try the Dashboard

Explore a sample property report

A working sample of the Scapely Dashboard. Search the three sample properties, jump between report sections and stress-test costs and strategies. Everything here is sample data running in your browser.

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Samples
Property report (sample)

24 Coleherne Road

Score 67/100
SW10 9BWRoyal Borough of Kensington and ChelseaMid-terrace house6 rooms152 sqmPre-1900
01

Quick stats

EPC rating, transport access, HMO density and flood risk at a glance.

EPC Rating
E

Potential C with works.

PTAL Score
6a

Excellent

HMO Density
14%

Moderate saturation.

Flood Risk
Zone 1

low probability of flooding.

02

Sale history

Registered transactions and nearby comparables to benchmark the price.

Last registered sale
£1,850,000
Comparable average
£1,736,667
Comparables vs last sale
-6.1%
  • 18 Coleherne Road£1,975,000
    8 Feb 2024
  • 31 Coleherne Road£1,690,000
    14 Sept 2022
  • 9 Coleherne Road£1,545,000
    3 Nov 2021
  • 24 Coleherne RoadSubject£1,850,000
    12 Apr 2019
  • 24 Coleherne RoadSubject£1,420,000
    6 Jul 2011

Sample records styled on HM Land Registry Price Paid Data. Not real transactions.

03

Property fundamentals

Heritage, tenure and neighbourhood deprivation shape consent and buyer appetite.

Deprivation
Decile 7

Index of Multiple Deprivation, 1 = most deprived, 10 = least.

MostLeast

England's IMD ranks every neighbourhood from most to least deprived.

Area information

Kensington and Chelsea 012B. Urban conurbation, high-value Victorian terraces and strong rental demand.

Royal Borough of Kensington and ChelseaMid-terrace house152 sqmPre-1900
Heritage status
Conservation Area

Not listed, but alterations in a Conservation Area need full planning consent.

Listing and conservation designations restrict alterations.

Tenure
Freehold

Full ownership, no lease or ground rent liabilities.

Freehold means outright ownership of the building and land.

Local authority
Sample

Royal Borough of Kensington and Chelsea

The authority whose planning policy applies to this plot.

04

Energy performance

Current rating and the cost and uplift of upgrading before selling or letting.

EPC uplift potential
Current
E
Headroom
+2 bands
Potential
C

SAP score moves from 48 to 79 with the modelled works.

Retrofit cost
£22,400

£18,200 to £28,600

Indicative spend to reach the potential band.

Capital uplift
+6.5%

Greener-homes value premium per band achieved.

Rental uplift
+4.2%

Estimated rent premium per band achieved.

Annual bill saving
£1,840/yr

£3,120 to £1,280

Heating, hot water and lighting after improvements.

  • Air source heat pump£8,000 to £14,000saves £720/yr
  • Solid wall insulation (external)£9,000 to £15,000saves £540/yr
  • Secondary glazing£1,200 to £3,500saves £180/yr
05

Development potential

Planning risk, recommended route and a first-pass screen of permitted development rights.

Recommendation
Target strategyExplore refurbishment or a 4-bed HMO, subject to planning permission
Planning risks · Sample: not a higher-risk building (low-rise house)
Overall riskMedium

Illustrative sample only. It assumes Conservation Area and Article 4 restrictions that limit permitted development. Extensions may need planning consent. Where an Article 4 direction removes C3 to C4 rights, an HMO conversion requires a planning application, not prior approval.

Key objection themes
Conservation Area characterArticle 4: HMO restrictionsNeighbour amenityHeritage materials policy
C3 to C4 HMO conversion
Part 3, Class L
Restricted
Sample Article 4 restriction: planning permission required for C3 to C4 conversion.
  • The sample assumes an Article 4 direction removes Class L permitted development rights.
  • Apply for planning permission; prior approval does not replace removed permitted development rights.
Rear extension
Part 1, Class A
Restricted
Up to 3m permitted in principle, subject to Conservation Area materials criteria.
  • Materials must match original Victorian stock.
  • Anything above eaves height needs full consent.
Additional storey
Part 1, Class AA
Not available
Not available within a Conservation Area.
  • Class AA rights do not apply in designated Conservation Areas.

Sample first-pass screen. The live Dashboard checks the real constraints for any address.

06

Commercial and levies

Class MA, CIL, MEES and biodiversity net gain obligations.

Class MA
Not eligible

Residential (C3). Class MA applies to commercial Class E only.

PD right to convert commercial premises to homes.

CIL Zone 3
£125/sqm

Verify against the current charging schedule.

Community Infrastructure Levy on new floorspace.

Commercial MEES
Check

Sample EPC E. Commercial lets in England and Wales currently need at least EPC E, with exemptions. Domestic rules are separate, and proposed changes are not yet law.

Current rented non-domestic EPC rules in England and Wales are separate from proposed future standards. Check exemptions, use and jurisdiction.

BNG
Low

Existing residential: negligible obligation unless adding new footprint.

Biodiversity Net Gain: a measurable 10% habitat improvement.

Sample data for demonstration only. No searches, payments or accounts are used here.Run a real report in the Dashboard

Sources and methodology

Reviewed by the Scapely editorial team on 23 October 2026.

Build-cost and market figures on this page are indicative Scapely editorial benchmarks used for screening. They are not quotes, valuations or live data, and they have not been checked against a cost consultant. Real costs vary with specification, access, scale and date.

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