Planning permission vs permitted development vs Lawful Development Certificates.

What is Permitted Development?

Permitted development (PD) rights are a set of automatic planning permissions granted by Parliament through the Town and Country Planning (General Permitted Development) (England) Order 2015 (as amended). They allow homeowners to carry out certain types of building work without submitting a planning application to their local council.

PD rights are organised into Classes. The ones most relevant to London homeowners are:

• Class A — Enlargement, improvement or other alteration of a dwellinghouse. This covers rear extensions, side extensions, and internal alterations that change the external appearance. Single-storey rear extensions can project up to 3 metres from the rear wall (attached/semi-detached) or 4 metres (detached). Maximum height is 4 metres at the eaves. Two-storey rear extensions are limited to 3 metres depth with a 7-metre eaves restriction and must be at least 7 metres from the rear boundary.
• Class B — Additions to the roof of a dwellinghouse. Loft conversions, including rear dormers, can add up to 40 cubic metres of additional roof space on terraced houses, or 50 cubic metres on semi-detached and detached houses. The dormer must be set back at least 20 cm from the original eaves. Materials must match the existing house in appearance as closely as possible.
• Class C — Other alterations to the roof. Re-roofing, changing roof tiles, and adding rooflights that do not protrude more than 150 mm above the roof plane.
• Class D — Porches. A porch can be added without planning permission if it is no more than 3 square metres in floor area, no higher than 3 metres, and is at least 2 metres from any boundary fronting a highway.
• Class E — Buildings incidental to the enjoyment of a dwellinghouse. Garden rooms, sheds, greenhouses and outbuildings. These must not cover more than 50% of the garden area, must be single-storey, and must not be used for habitable accommodation (sleeping, cooking or sanitary facilities).

There are critical constraints that apply across all classes. Materials used in any extension must be similar in appearance to the existing dwelling. No part of the extension can be higher than the highest part of the existing roof. Extensions to the front elevation or facing a highway are generally not permitted. And on designated land — including conservation areas, Areas of Outstanding Natural Beauty, and National Parks — PD rights are significantly reduced.

It is important to understand that permitted development rights apply only to houses (Use Class C3). They do not apply to flats, maisonettes, or buildings that have been converted from commercial use. If your property was created by a prior approval conversion (for example, from office to residential under Class O or Class MA), your PD rights may have been removed by condition.

What is a Lawful Development Certificate?

A Lawful Development Certificate (LDC) is an official document issued by your local planning authority confirming that a particular development is — or was — lawful. It is not planning permission. It is proof that planning permission was not required.

There are two types:

• Proposed LDC (Section 192) — confirms that a development you intend to carry out falls within permitted development rights. You apply before you build. This is the type most commonly used for house extensions and loft conversions. The council application fee is £103.
• Existing LDC (Section 191) — confirms that a development that has already been completed was lawful at the time it was carried out. This is used when you need retrospective proof, often for a property sale. The council application fee is £206.

The council must determine an LDC application within 8 weeks. Unlike full planning permission, the council cannot refuse an LDC based on design quality, neighbour objections, or policy preferences. The only question they assess is: does this development fall within the legal definition of permitted development? If the answer is yes, they must issue the certificate.

Why should you get one? Because without an LDC, you have no official proof that your extension was built lawfully. This matters enormously when you come to sell. Conveyancing solicitors acting for buyers will ask for evidence that any extensions or alterations were carried out with appropriate permissions. An LDC is the cleanest, most defensible document you can provide. Without one, you may need to purchase indemnity insurance — and some buyers or lenders will refuse to proceed without formal evidence.

An LDC application requires detailed architectural drawings showing the existing property and the proposed development, with measurements demonstrating compliance with every PD limit. This is where most homeowners need professional help. The drawings must prove compliance with millimetre precision — if a dormer is 21 cm from the eaves instead of the required 20 cm, the application is straightforward; if it is 19 cm, it will be refused.

When do you need full planning permission?

Full planning permission (formally called a "householder planning application") is required when your project falls outside permitted development limits, or when your PD rights have been removed. Common triggers include:

• Conservation areas. PD rights are significantly restricted in conservation areas. Side extensions, cladding, and any extension visible from a highway or public space generally require full planning permission. Rear extensions are limited to single-storey under PD.
• Listed buildings. Any alteration to a listed building — internal or external — requires listed building consent, which is a separate application from planning permission. PD rights do not apply to listed buildings in any meaningful way.
• Article 4 Directions. A council can issue an Article 4 Direction to remove specific PD rights in a defined area. This is common across inner London boroughs, particularly in conservation areas. If your property is subject to an Article 4 Direction, you may need full planning permission for work that would otherwise be permitted development.
• Flats and maisonettes. PD rights under the GPDO apply only to dwellinghouses. If you live in a flat, even a ground-floor flat with a garden, you cannot use PD rights for extensions. Full planning permission is required.
• Change of use. Converting a house into flats (C3 to C4 or sui generis), or converting a commercial unit to residential use, requires either full planning permission or a Prior Approval application (see below).
• Exceeding PD size limits. A rear extension deeper than 3 metres (or 4 metres for detached), a loft conversion exceeding 40/50 cubic metres, or a two-storey extension deeper than 3 metres will all require full planning permission.
• Front extensions and major external alterations. PD rights do not generally cover extensions to the principal elevation. Any extension visible from the highway that changes the front appearance of the dwelling requires planning permission.

The council application fee for a householder planning application is £258. The determination period is 8 weeks. The council will assess your application against its Local Plan policies, the National Planning Policy Framework, and any relevant supplementary planning documents. Neighbours are consulted, and their objections are a material consideration — though not a decisive one.

For London projects, you should also be aware that some boroughs have additional local restrictions. Basement development is heavily restricted in several boroughs (including Kensington and Chelsea, Camden, and Westminster). Roof extensions visible from the street are often resisted in conservation areas even where PD rights technically apply. A pre-application meeting with the council (£150–£600 depending on borough) can save significant time and cost.

PD vs LDC vs full planning: comparison

Prior Approval: the fourth route

Prior Approval is a streamlined planning process that falls between permitted development and full planning permission. It applies to specific categories of development where Parliament has decided that the principle of development is acceptable, but the council may still assess certain limited impacts.

The most relevant Prior Approval routes for London homeowners and developers are:

• Larger home extensions (Class A, paragraph A.4). Single-storey rear extensions between 4–8 metres (detached) or 3–6 metres (all other houses) can be built under Prior Approval. The council notifies adjoining neighbours, who have 21 days to respond. The council then has 42 days to decide, assessing only the impact on the amenity of adjoining properties. If the council does not respond within 42 days, approval is deemed granted.
• Commercial-to-residential conversions (Class MA). This replaced the former Class O (office to residential). It allows the change of use from Class E (commercial, business and service) to Class C3 (residential) subject to Prior Approval. The council assesses transport, contamination, flooding, noise, natural light, fire safety, and the impact on the provision of local services. The building must have been in commercial use for at least 2 continuous years before the application. There is a floor space limit of 1,500 square metres.
• Upward extensions (Class AA). This relatively new right allows the construction of up to 2 additional storeys on top of existing purpose-built detached blocks of flats (3+ storeys) or on certain detached commercial buildings. The council assesses external appearance, air traffic and defence, impact on neighbours, and the provision of adequate natural light. This route is increasingly used in London for densification without full planning.

Prior Approval applications typically cost £120 and must be determined within 56 days. The key difference from full planning permission is that the council can only assess the specific impacts listed in the legislation — they cannot refuse on broader policy grounds such as housing mix, affordable housing contributions, or design quality beyond the specified criteria.

How Article 4 Directions change everything

An Article 4 Direction is a legal order made by a local council that withdraws specific permitted development rights in a defined area. When an Article 4 Direction applies to your property, work that would normally be permitted development instead requires full planning permission.

Article 4 Directions are widespread across London, particularly in conservation areas. They are used to give councils greater control over changes that could harm the character of sensitive areas. Common restrictions include:

• Removal of PD rights for rear dormer loft conversions
• Restrictions on window and door replacements (especially uPVC in Victorian/Edwardian terraces)
• Controls on painting, rendering or cladding external walls
• Restrictions on satellite dishes, aerials and solar panels visible from the highway
• Removal of rights for outbuildings, garden structures and boundary treatments

London boroughs with particularly extensive Article 4 coverage include:

• Camden — covers most conservation areas borough-wide
• Islington — extensive Article 4 covering almost all conservation areas
• Westminster — near-blanket Article 4 across the borough
• Kensington and Chelsea — widespread conservation area Article 4s
• Hackney — growing coverage, especially in De Beauvoir, Dalston and Stoke Newington
• Richmond upon Thames — extensive conservation area coverage
• Lambeth — Article 4s in Brixton, Clapham and Streatham conservation areas
• Haringey — Muswell Hill, Hornsey and Crouch End areas
• Wandsworth — multiple conservation area Article 4s
• Southwark — Dulwich, Bermondsey and Borough areas

Before starting any project, check whether your property is affected by an Article 4 Direction. Your council's planning department or interactive planning map will confirm this. If an Article 4 applies, budget for a full planning application rather than relying on PD rights.

Which route is right for your project?

The decision tree is more straightforward than it appears. Work through these questions in order:

1. Is your property a house (Use Class C3)? If you live in a flat, maisonette, or a converted commercial unit where PD rights were removed by condition, you need full planning permission for any extension work. Stop here.

2. Is your property listed? If yes, you need listed building consent (plus planning permission if external work is involved). PD rights are effectively irrelevant. Stop here.

3. Is your property in a conservation area or subject to an Article 4 Direction? Check your council's interactive map. If an Article 4 removes the specific PD right you need, you will require full planning permission. If you are in a conservation area without an Article 4, PD rights still apply but with restrictions (no side extensions, no cladding, single-storey rear only).

4. Does your project fall within PD size limits? Measure carefully. If your rear extension is under 3 metres (or 4 metres detached), your loft conversion adds under 40 cubic metres (50 detached), and all other conditions are met, you can proceed under permitted development. We strongly recommend applying for a Lawful Development Certificate to obtain official proof.

5. Does your project exceed PD limits but remain single-storey? If you want a larger single-storey rear extension (up to 6 metres, or 8 metres detached), consider the Prior Approval route for larger home extensions. It is faster and cheaper than full planning, and the council can only assess impact on neighbours.

6. Does your project exceed all PD routes? You need full planning permission. Consider a pre-application meeting with the council to understand their likely position before investing in a full drawing set.

If you are unsure, get in touch for a free assessment. Our chartered architectural technologists can confirm your route in a single conversation and provide a fixed-fee quote for the drawings you need.

Frequently asked questions