Permitted Development in London, Decoded (2026)

What is permitted development, and what does it cover?

Permitted development is a national grant of planning permission for certain works, so long as they stay within defined limits. For a typical house it can cover single-storey rear extensions, some side extensions, loft conversions within volume limits, outbuildings, and changes like porches and rooflights. The rights come with conditions on depth, height, materials and how much of the plot you cover — exceed any one of them and the whole project needs full planning permission.

• Single-storey rear extensions within depth limits (typically 3m terraced/semi, 4m detached; larger sizes need Prior Approval)
• Loft conversions within volume limits — 40m³ terraced, 50m³ detached and semi-detached
• Outbuildings, porches, and most rooflights that do not project beyond the roof plane
• Rear dormers on many houses — but not usually on the front roof slope

Do I need a Lawful Development Certificate for permitted development?

No — legally you can build permitted development without applying for anything. But that leaves you carrying the risk. A Lawful Development Certificate (LDC) is a formal decision from the council confirming that your specific project is lawful. It is the document a buyer's solicitor will ask for, the thing that ends a neighbour dispute before it starts, and your defence if the council ever queries the work. For a few hundred pounds of council fee and a set of accurate drawings, it converts an assumption into certainty.

The LDC test is different from a planning decision, and that difference is in your favour. An LDC application is not judged on whether the design is attractive or whether neighbours object — it is a factual test of whether the works meet the permitted-development rules. There is no neighbour consultation and no discretion: if the drawings prove compliance, the certificate is issued. That is why an LDC, backed by accurate drawings, is both faster in spirit and lower-risk than a full application, and why it is worth having even though nobody can force you to obtain one.

What is an Article 4 direction and why does it matter in London?

An Article 4 direction is a tool councils use to remove specified permitted-development rights in a particular area — usually to protect the character of a conservation area or to control the spread of houses in multiple occupation. Large parts of inner London are covered: several Islington, Camden and Waltham Forest neighbourhoods have Article 4 directions that mean works which would be PD elsewhere need a full planning application here. Because Article 4 is drawn street by street, two identical houses a few roads apart can have completely different rights, so a neighbour's recent extension is no guarantee that the same works are permitted at your address.

• Conservation-area Article 4s often remove PD for front alterations, cladding, and sometimes rear extensions
• HMO Article 4s (borough-wide in some London boroughs) require planning to convert a family house to a shared house
• The only reliable check is the council's own designation map for your exact address, because Article 4 boundaries follow historic street patterns rather than any logic you could guess from the outside

Does permitted development apply to flats and maisonettes?

Largely no. The permitted-development rights for extensions and loft conversions apply to houses, not to flats or maisonettes — so a great deal of London's housing stock is excluded from the outset. This surprises many owners of converted-house flats, who assume their share of the building carries the same rights as the house did; it does not. Works to a flat almost always need a full planning application, and usually freeholder consent under your lease and a party-wall process with the flats above or below as well. If you own a flat or maisonette, treat PD as unavailable and plan for the full route — planning, lease consent and party wall — from day one, because discovering the restriction after committing to a builder is an expensive way to learn it.

How close to the limits can I really build?

The permitted-development limits look generous on paper, but they are a cliff edge, not a slope: meet every one and the whole project is lawful without a planning application; miss a single one by a few centimetres and the entire scheme needs full planning permission. There is no partial credit. This is why so many homeowners come unstuck — they design to the number they remember, forget one of the conditions that sits alongside it, and only discover the problem when a buyer's solicitor or an enforcement officer reads the drawings years later. It pays to understand the two areas where projects most often tip over the edge.

The safest way to build near a limit is to measure the existing house accurately first, then design with a deliberate margin rather than shaving against the maximum. A centimetre of tolerance costs nothing on a drawing and saves a full planning application later, whereas a scheme squeezed against every maximum leaves no room for the small on-site variations that are almost inevitable in construction.

Permitted development or full planning — which route should I choose?

If your project fits comfortably inside the limits and there is no Article 4 direction on your street, the PD route with a Lawful Development Certificate is faster, cheaper and lower-risk. If you are close to any limit, in a conservation area, extending upward or to the side, or own a flat, the full planning route is the honest answer — and trying to force a borderline scheme through PD usually costs more when it unravels.

The mistake to avoid is treating the two routes as interchangeable and simply picking the cheaper one. They test different things: PD is a factual compliance test with no discretion, while full planning is a judgement about acceptable design, so a scheme that is borderline on PD is not automatically weak on planning — sometimes the full application is the stronger, safer path even though it costs a little more. We assess which route your property actually qualifies for before any drawings are commissioned, so the decision is based on your specific address rather than a general rule of thumb.