Planning Enforcement in London: What Happens If You Build Without Permission

Planning enforcement proceedings begin when a local planning authority becomes aware of a breach of planning control. Breaches of planning control that can lead to enforcement in London: development (building work, engineering operations, or material change of use) carried out without the required planning permission; development carried out in a manner that does not comply with the conditions of a planning permission; listed building works carried out without listed building consent; demolition of a building in a conservation area without planning permission. How councils find out about unauthorised development: complaints from neighbours (by far the most common trigger — a new extension, a roof terrace that creates overlooking, a change of use that generates noise or traffic); aerial photography or satellite imagery review (councils and the Planning Inspectorate regularly review aerial photography to identify apparent new development); the planning application process itself (when applying for planning permission for a later project, the drawings may reveal previous unauthorised work); and disclosure during a property sale (a buyer's solicitor raising enquiries about building works).

A London council has several enforcement tools: Breach of Condition Notice (BCN): issued where a planning condition attached to an existing permission has been breached. The BCN requires the breach to be remedied within a specified period (minimum 28 days). Failure to comply with a BCN is a criminal offence (unlike an Enforcement Notice). Planning Enforcement Notice (EN): issued where the council considers that: a breach of planning control has occurred; it is expedient to issue an enforcement notice having regard to the development plan and other material planning considerations. The EN specifies: the alleged breach; what steps must be taken to remedy it; the time period for compliance (typically 28 days to 6 months). An EN can be appealed to the Planning Inspectorate within 28 days of issue (see the planning appeals guide). Stop Notice: can be issued alongside an Enforcement Notice where the council considers the breach must stop immediately (used for the most serious or harmful breaches). Listed Building Enforcement Notice: the specific form of enforcement notice for unauthorised listed building works. Untreated London cases: councils are not obliged to take enforcement action in every case — they have a discretion. Many technical breaches of planning control in London are de minimis (harmless) and councils choose not to pursue enforcement. The National Planning Policy Framework (NPPF) guidance on enforcement states: 'Effective enforcement is important as a means of maintaining public confidence in the planning system... Enforcement action is discretionary, and local planning authorities should act proportionately in responding to suspected breaches of planning control.'

One of the most important protections for London homeowners with unauthorised development is the limitation period — after which the council's right to take enforcement action expires: Operational development (building work — extensions, loft conversions, outbuildings): 4 years from the date the development was substantially completed. If the development was completed more than 4 years ago and no enforcement action has been taken, the right to enforce expires. The homeowner can apply for a Lawful Development Certificate (LDC) for existing development confirming the development is now lawful through the passage of time. Change of use to a dwellinghouse: 4 years from the date of the change of use. Any other change of use: 10 years from the date of the change of use. Breach of a planning condition: 10 years from the date of the breach. Important change to limitation periods: the Levelling Up and Regeneration Act 2023 changed the limitation period for unauthorised operational development from 4 years to 10 years for development starting after 25 April 2024. Development that started before 25 April 2024 retains the 4-year limitation period. This is an important change that means newer unauthorised extensions and loft conversions in London (after April 2024) will need to wait 10 years rather than 4 years for the enforcement limitation to expire.

Where planning permission was required and not obtained for work in London, the most straightforward remedy (where the work can be approved) is to apply for retrospective planning permission: Retrospective planning application (s73A application): an application for planning permission made after the development has been carried out. The council assesses the development using the same criteria as a standard application — against the development plan, the London Plan, and all relevant material considerations. If the development would have been approved if applied for in advance, it should be approved retrospectively. Important: a retrospective application is not automatically granted — if the development would have been refused had it been applied for in advance, it will be refused retrospectively too. The benefit of a retrospective approval: regularises the planning position; resolves the issue for the purposes of property sale; provides the buyer's solicitor with evidence that the development is lawful; and removes the enforcement risk. Retrospective applications that are refused: the council may still issue an Enforcement Notice requiring the works to be remedied (demolished or altered to comply with the conditions of a consent). A Lawful Development Certificate for existing use: where the 4-year (or now 10-year) limitation period has expired, the homeowner can apply for an LDC for existing development rather than a retrospective planning application. The LDC is evidence that the development is now beyond the enforcement time limit — and cannot be the subject of enforcement action regardless of whether it would have been approved.

The most common context in which unauthorised London development becomes a problem is the property sale: Standard conveyancing enquiries: the buyer's solicitor will raise enquiries (typically via the CON 29 local authority search) about planning enforcement notices and planning history. The seller is under a duty to disclose enforcement notices. Separate solicitor enquiries will ask the seller directly whether any building work has been carried out and whether the required consents were obtained. Implications for a London property sale with unauthorised development: the buyer's solicitor will typically require either: (1) evidence of retrospective planning permission; (2) a Lawful Development Certificate (where the limitation period has expired); or (3) an indemnity insurance policy covering the risk of enforcement action. Planning indemnity insurance: available from specialist UK legal indemnity insurers (Aviva, ARAG, CLS, Defaqto). Typical cost for a London residential property: £200-£1,500 as a one-off premium. Covers the cost of enforcement action, legal fees, and any loss in value from a successful enforcement action. Not available where: the unauthorised development has already been notified to the council or is already the subject of enforcement proceedings; the development is less than a few years old (insurers require the limitation period to be approaching, not recently started). Planning indemnity insurance is a legitimate solution for a property sale when retrospective permission is not possible or the development is approaching the limitation period — but it is not a substitute for planning permission where the development can and should be regularised.