Permitted Development Rights for Extensions: What You Can Build Without Planning Permission in London

**The legal basis for permitted development rights for extensions**:

Permitted development rights for extensions to dwelling houses are contained in Part 1, Class A of Schedule 2 to the Town and Country Planning (General Permitted Development) (England) Order 2015 (GPDO 2015), as amended.

• Permitted development rights only apply to:
• •The existing dwelling house (not flats; not maisonettes; not purpose-built student accommodation)
• •In England (not Wales; not Scotland; not Northern Ireland — each has its own PD regime)
• •Where PD rights have not been removed by a planning condition, Article 4 Direction, or prior planning condition

**Class A PD rights — the key limits for London extensions**:

*Single-storey rear extensions under Class A PD*:

The maximum permitted extension dimensions for a single-storey rear extension under Class A PD rights (where no Prior Approval is needed) are:

| Property type | Maximum depth from original rear wall | Maximum height | |---|---|---| | Detached house | 4.0 metres | 4.0m (eaves); 4.0m ridge | | Semi-detached or terraced house | 3.0 metres | 4.0m (eaves); 4.0m ridge |

*Note*: the 4.0m/3.0m depth limits above are the standard PD limits where NO Prior Approval is needed. Where Prior Approval is obtained under the 'Larger Home Extension Scheme' (LHES), single-storey rear extensions can be built to:

| Property type | Maximum depth WITH Prior Approval | |---|---| | Detached house | 8.0 metres from the original rear wall | | Semi-detached or terraced house | 6.0 metres from the original rear wall |

See the Prior Approval section below for the process.

• *Additional conditions applicable to all Class A single-storey rear extensions*:
• •Height of the extension at the eaves: maximum 3.0m if within 2.0m of the boundary
• •Height of the extension: must not exceed the height of the existing dwelling house
• •The extension must not extend beyond the front elevation of the dwelling house
• •Materials: the extension must be built in materials of similar appearance to the existing dwelling house (this applies to PD extensions in conservation areas as well as non-conservation areas, although conservation area Article 4 Directions often withdraw PD rights entirely)
• •No verandas, balconies, or raised platforms
• •No side-facing windows or rooflights within 1.0m of the boundary (unless obscure-glazed)
• •The floor area of any outbuildings on the site (including the proposed extension) must not exceed 50% of the total curtilage of the property (excluding the footprint of the original house)

*Double-storey rear extensions under Class A PD*:

A double-storey rear extension (i.e., an extension that adds habitable floor space on both the ground floor and first floor) can be built under PD rights, subject to stricter limits:

| Condition | Limit | |---|---| | Maximum depth from original rear wall | 3.0 metres | | Maximum height | Must not exceed the height of the existing dwelling house | | Distance from boundary | The extension must be at least 7.0 metres from the opposite rear boundary | | Eaves height | Must match or not exceed the eaves height of the existing dwelling house | | Roof pitch | Must match the existing dwelling house |

*In practice, double-storey rear extensions under PD rights are relatively unusual in London Victorian terrace configurations*: the requirement for a 7.0m setback from the rear boundary typically means that on narrow London plots (rear garden depths of 8–12m), there is insufficient room to achieve the 3.0m extension depth AND the 7.0m setback from the rear boundary simultaneously. Most London double-storey extensions require planning permission.

*Side extensions under Class A PD*:

Side extensions are permitted under Class A PD subject to the following key conditions:

| Condition | Limit | |---|---| | Width of single-storey side extension | Maximum 50% of the width of the original dwelling house | | Height | Must not exceed the height of the existing dwelling house | | The extension must not be forward of the principal elevation | | In a designated area (conservation area; listed building; AONB; National Park) | Side extensions require planning permission — PD rights for side extensions are withdrawn |

*Key point for London*: the restriction on side extensions in designated areas (including all London conservation areas — of which there are over 1,000 in Greater London) means that most London Victorian terrace properties within a conservation area CANNOT build a side extension under PD rights. A side return extension on a London Victorian terrace in a conservation area always requires planning permission.

• *Side extensions under PD — further conditions*:
• •Must be single-storey (not two-storey)
• •No side-facing windows or rooflights within 1.0m of the boundary unless obscure-glazed
• •Materials must match the existing dwelling house

**What is the Prior Approval Larger Home Extension Scheme (LHES)?**

The Larger Home Extension Scheme (LHES) is a procedure introduced by amendment to the GPDO in 2013 (and made permanent in 2019) that allows single-storey rear extensions larger than the standard PD limits (4.0m detached / 3.0m semi-detached or terraced) to be built without full planning permission, subject to a 'Prior Approval' notification process with the LPA.

• Under the LHES, the extended depth limits are:
• •Detached house: up to **8.0m** from the original rear wall
• •Semi-detached or terraced house: up to **6.0m** from the original rear wall

All other Class A conditions still apply (height; materials; no verandas; no side windows within 1.0m of boundary; etc.)

**The LHES Prior Approval process**:

• *Step 1 — Notification to the LPA*:
• Before starting work, the homeowner must notify the LPA (the London Borough) using the standard Prior Approval notification form (available on the Planning Portal and each Borough's planning portal). The notification must include:
• •A plan showing the site and the proposed extension
• •A plan showing the floor plan of the proposed extension
• •Details of the proposed materials
• •Addresses of all adjoining dwellings (properties that share a wall, rear boundary, or side boundary with the property)

*Step 2 — LPA notifies neighbours*: On receipt of the Prior Approval notification, the LPA must notify each adjoining dwelling owner and occupier that the proposed extension is intended to be carried out under the Larger Home Extension Scheme, that they have an opportunity to object, and that objections should be received within 42 days of the date of the LPA's notification.

*Step 3 — LPA considers any objections*: If no objections are received from adjoining owners within the 42-day consultation period, the extension may proceed without any formal LPA approval — the homeowner need not wait for the LPA to issue a decision; the 42-day consultation period is the only check.

• If one or more adjoining owners DO object within the 42-day period:
• •The LPA must consider ONLY the impact of the proposed extension on the amenity of the adjoining property — NOT its wider planning impact; NOT its appearance from the street; NOT its impact on the character of the area
• •The LPA issues a Prior Approval decision (approval or refusal) within 42 days of the LPA's notification to neighbours
• •If the LPA refuses Prior Approval, the homeowner may either modify the extension (e.g., reduce the depth to within the standard PD limits) or apply for full planning permission

**LHES Prior Approval — practical considerations for London extensions**:

*The 'original rear wall' reference point*: the LHES depth is measured from the 'original rear wall' of the dwelling house — this means the rear wall of the original house as it existed at 1 July 1948 (or as first built if built after 1 July 1948). Previous extensions (including conservatories added after 1948) do not move the measurement reference point — the depth is always from the 'original' rear wall. This is an important distinction: if a previous extension has already used some or all of the standard PD depth, a LHES Prior Approval may not give as much additional depth as expected.

*Lawful Development Certificate (LDC) as confirmation*: once the LHES process is complete (Prior Approval granted or 42-day consultation period expired with no objections), it is strongly advisable to obtain a Lawful Development Certificate from the LPA confirming that the extension is lawful under PD rights. The LDC provides formal legal documentation that the extension is permitted — important for property sale and mortgage purposes.

• *LHES not available in certain cases*:
• •Flats and maisonettes — only houses
• •Listed buildings
• •Where planning conditions on the existing house remove PD rights (see below)
• •Where the article 4 direction withdraws PD rights for rear extensions (see below)
• •Where the extension is two-storey (LHES only applies to single-storey rear extensions)

**Important conditions and triggers that REMOVE Class A PD rights for extensions in London**:

• *1. Conservation Area Article 4 Directions*:
• In conservation areas, London Boroughs can make and have made Article 4 Directions that withdraw some or all Class A PD rights. The most commonly withdrawn PD rights in London conservation areas:
• •Class A side extensions: side extensions in conservation areas require planning permission regardless of size (this applies nationally under the GPDO designation restrictions, not just through Article 4)
• •Class A front extensions: planning permission required for any extension visible from the highway in conservation areas
• •Some Boroughs have made specific Article 4 Directions withdrawing rear extension PD rights in conservation areas — check the specific Borough's conservation area designations and Article 4 Directions

*2. Planning conditions on the existing planning permission*: Where planning permission was granted for the original house, or for a previous extension, a planning condition may have been attached that removes some or all PD rights. Common wording: 'Notwithstanding the provisions of the Town and Country Planning (General Permitted Development) Order 2015 (or any order revoking and re-enacting that order), no extensions, outbuildings, or alterations to the roof of the dwelling hereby approved shall be erected without the prior consent of the Local Planning Authority.' This type of condition is common on new-build developments in London where the LPA has imposed it to control cumulative impacts on the development design.

*3. Flats, maisonettes, and other non-dwelling house uses*: Class A PD rights apply only to dwelling houses (as defined by Use Class C3). Flats and maisonettes (whether converted Victorian houses or purpose-built blocks) do not have Class A PD rights — any extension, outbuilding, or alteration to a flat requires planning permission.

*4. Listed buildings*: Listed Building Consent (LBC) is required for any works to a listed building or its curtilage that affect the character of the building as a building of special architectural or historic interest. This means that even if PD rights technically apply to an extension proposal, LBC is still required for a listed building — and the works cannot be carried out under PD rights without LBC.

*5. PD rights previously used*: If previous extensions have been built using PD rights, those extensions may have used up part or all of the PD depth allowance. The measurement is always from the 'original' rear wall — so if a previous extension extends 2.0m from the original rear wall, only a further 1.0m of extension (to reach the 3.0m PD limit for a semi-detached) is available under PD rights for the combined extension.

**How to check PD rights before starting a London extension**:

1. Check whether your property is in a conservation area (London Borough planning portal or the Borough's Conservation Area maps) 2. Check whether the property is listed (Historic England's listed buildings register at historicengland.org.uk/listing/the-list) 3. Check the planning history of the property on the Borough portal (look for any planning conditions removing PD rights) 4. Check whether any previous extensions have used PD depth allowance 5. Apply for a Lawful Development Certificate (LDC) from the LPA (Section 192, TCPA 1990) confirming the proposed extension is lawful — the gold standard confirmation that PD rights apply and the proposal meets all conditions. LDC applications cost £206 (residential application) and are determined in 8 weeks. This is the most reliable protection before starting work.

**Why a Lawful Development Certificate (LDC) matters for London extension PD works**:

• The consequences of starting an extension that is not, in fact, permitted development (because PD rights have been removed by a planning condition, Article 4 Direction, or other restriction that was not identified) are serious:
• •The LPA may issue an Enforcement Notice requiring the extension to be removed
• •The extension, if built without planning permission where required, is an unauthorised development — a material concern for property sale and mortgage purposes
• •Retrospective planning permission is possible (planning permission after works are completed), but is not guaranteed to be granted, and the extension must be removed if retrospective permission is refused

**The LDC protects the homeowner**:

A Lawful Development Certificate, once issued by the LPA, is formal legal documentation that the specific works described are lawful as permitted development. It cannot be challenged retrospectively by the LPA (even if the LPA later discovers that PD rights were removed by a condition it had forgotten). An LDC issued in error by the LPA does not create a criminal liability for the homeowner.

**LDC application for a proposed extension under PD**:

*Application type*: Section 192 TCPA 1990 — Lawful Development Certificate for proposed use or development *Fee*: £206 (residential; 2025 fee, same as for full householder planning permission) *Information required*: site location plan; proposed extension plans; completed LDC application form describing how the extension meets all the conditions of the relevant PD class *Determination period*: 8 weeks (same as a householder planning application) *Outcome*: LDC issued (extension confirmed as lawful PD) or refused (extension is not lawful as PD — apply for planning permission instead)

**Cost comparison: LDC + extension under PD vs. Planning Permission**:

| Route | Fee | Determination period | Scope limitation | |---|---|---|---| | LDC (proposed PD) | £206 | 8 weeks | Must comply with all PD conditions | | Full householder PP | £258 (2025 fee) | 8 weeks | LPA can impose conditions; can refuse | | Prior Approval (LHES) | £120 | Up to 42 days | Only single-storey rear; amenity only |

*For a standard London extension within PD limits, the LDC route (£206; 8 weeks; no planning conditions imposed) is generally preferable to the planning permission route — provided the proposal genuinely qualifies as PD. The £52 saving over PP is not the main benefit; the main benefit is that no planning conditions can be imposed on an LDC.*

**When planning permission is the right route for London extensions**:

• *Planning permission (full householder application) is required, or is the better route, where*:
• •The extension does not qualify as PD (too large; in a conservation area with restricted PD rights; flat or maisonette; listed building)
• •The homeowner wants to build a larger extension than PD allows
• •The design of the extension requires flexibility in materials or height that is not possible under PD conditions
• •The property is in a conservation area and the LPA's pre-application guidance confirms planning permission is needed
• •The homeowner wants the certainty of an approved planning permission (some buyers prefer properties with full planning permission for the extension rather than an LDC, particularly for larger extensions)

For most standard single-storey London rear extensions within 3.0m (semi/terrace) or 4.0m (detached), outside conservation areas, and without planning conditions removing PD rights: an LDC is the efficient and reliable route. For extensions beyond these limits, or in conservation areas, planning permission is required.