Planning Permission in London: What Contractors Need to Know (2026)

Planning questions come up on almost every domestic job in London — and getting the answer wrong can stop a project entirely, or expose your client to enforcement action after the work is done. This guide cuts through the jargon to give contractors a clear picture of what needs permission, what does not, and where London's particular quirks make the national rules nearly irrelevant.

Permitted Development Rights: what you can build without planning permission

Permitted Development (PD) rights allow certain works to go ahead without a formal planning application. For residential properties in England, the key thresholds for common jobs are:

Rear extensions (single-storey):

• Detached houses: up to 4 metres beyond the original rear wall.
• Semi-detached and terraced houses: up to 3 metres beyond the original rear wall.
• Maximum height 4 metres; eaves no higher than the existing eaves.

Loft conversions:

• Detached houses: up to 50 cubic metres of additional roof space.
• Terraced and semi-detached houses: up to 40 cubic metres of additional roof space.
• No extension beyond the existing roof slope on the principal (street-facing) elevation.
• Dormers are permitted on rear elevations under these limits, subject to materials matching.

When you do need planning permission

Several common types of work fall outside Permitted Development and require a full householder planning application:

• Front extensions of any size — any extension in front of the principal elevation.
• Side extensions that exceed half the width of the original house.
• Two-storey rear extensions — PD only applies to single-storey.
• Any work in a conservation area or on a listed building — see below.
• Article 4 Direction areas — where the council has specifically removed PD rights.
• Extensions exceeding the PD limits in height, projection, or volume.
• Changes of use — converting a commercial unit to residential, adding a separate self-contained flat, etc.

London boroughs with strict Article 4 directions

This is where London diverges sharply from national guidance. Article 4 Directions allow councils to remove Permitted Development rights in specific areas, typically to protect the character of Victorian and Edwardian streetscapes. In practice, this means that work which would be PD in, say, a 1970s suburb in the Midlands, requires full planning permission in large parts of inner London.

The boroughs most frequently flagged by contractors are:

• Camden — extensive Article 4 coverage across conservation areas and much of the borough.
• Islington — Article 4 applies across most residential areas; the whole borough is effectively Article 4 for rear dormers.
• Hackney — large swaths of Victorian terraces are under Article 4 directions.
• Southwark — multiple conservation areas with Article 4 coverage.
• Kensington & Chelsea — almost the entire borough is within a conservation area or subject to Article 4 directions; standard PD rights rarely apply.

The planning process: what to expect and when

When a full householder application is required, the typical timeline runs as follows:

1. Pre-application enquiry — optional but recommended for anything non-standard. The council gives informal feedback on likely acceptability before you commit to a full application. Allows you to refine the scheme and flush out problems early. Most London boroughs charge for this service; expect 2–4 weeks for a response.
2. Application submission — full householder application submitted via the Planning Portal with drawings, forms, and fees. Validation typically takes 1–2 weeks; the council then notifies neighbours and consultees.
3. 8-week determination period — the statutory target for householder applications. In practice, many London boroughs take 10–12 weeks, particularly for applications in conservation areas or involving party wall issues.
4. Decision — approval (with or without conditions), refusal, or non-determination.
5. Appeal — if refused, the applicant has six months to appeal to the Planning Inspectorate. Appeals typically take a further 6–12 months. A planning consultant significantly improves the odds at appeal.

Planning costs: what to budget

Below are typical costs for a householder extension or loft conversion application in London. These should be included in your cost plan from the outset — clients rarely budget for them unless you put them in front of them early.

Fees correct as of April 2026. The householder application fee is set nationally; all other costs vary by project and borough.

How BuildPilot accounts for planning costs

Most estimating tools treat planning as an afterthought — a vague allowance buried in preliminaries, or worse, left out entirely. When your client then gets a bill for architectural drawings, party wall surveyors, and planning fees they were not expecting, it reflects badly on your initial cost plan.

BuildPilot cost plans include planning-related costs as separate, itemised NRM2 line items: the planning application fee, an allowance for planning or architectural drawings, party wall surveyor fees where applicable, and a pre-application enquiry allowance where the project is in a sensitive area. These sit in the correct NRM2 section so funders and developers can see them clearly.

The result is a cost plan that holds up when the client actually starts spending money — rather than one that looks competitive at tender and falls apart at commitment stage.