Planning Enforcement in London — What Happens if You Build Without Permission?

Target keyword: planning enforcement London without permission Published by: RCB Design & Build | A2Z Principal Contractors Audience: Homeowners who have done works without planning permission, or who want to understand the risk

Building works without planning permission is more common than most homeowners realise — and the consequences are less straightforward than you might expect. Planning enforcement in England is not automatic, the law provides specific immunity periods in many circumstances, and there are legitimate legal routes for regularising past works. Understanding how the system actually operates is essential before you either start building without permission or purchase a property where unauthorised works have been carried out.

Is It a Criminal Offence to Build Without Permission?

In most cases, no. Under Section 171A of the Town and Country Planning Act 1990, carrying out development without planning permission is not in itself a criminal offence. What is an offence is failing to comply with an Enforcement Notice once one has been formally issued. This distinction matters: the local planning authority (LPA) must follow a procedural process before criminal liability arises, and even then it relates to non-compliance with the notice, not the original act of building.

There are limited exceptions — breach of a planning condition is governed differently (see below), and listed building enforcement carries separate and considerably more serious consequences.

The LPA's Discretion

The LPA is not obliged to take enforcement action even where a breach of planning control has occurred. Section 172 of the TCPA 1990 states that the LPA "may" issue an Enforcement Notice — not that it must. The National Planning Policy Framework 2023 (paragraph 59) reinforces that enforcement action should be proportionate to the breach. Minor works unlikely to cause any planning harm may simply be left without action.

This discretion does not mean the breach is approved or that the LPA has waived its rights. If circumstances change — for instance, if you apply for planning permission for something else and the LPA's attention is drawn to an existing breach — enforcement may follow.

Immunity Periods

Section 171B of the TCPA 1990 provides that the LPA loses the right to take enforcement action after certain time periods have elapsed without action being taken.

For operational development — the physical construction of a building or structure — the immunity period is four years from the date the development was substantially completed. If the LPA has not issued an Enforcement Notice within four years of completion, the development becomes immune from enforcement.

For material change of use to use as a single dwellinghouse, the immunity period is also four years.

For all other material changes of use, the immunity period is ten years from the date the change first took place, provided the use has continued throughout that period.

One critically important qualification: if the breach was concealed through deceit, the immunity period does not run. The Supreme Court confirmed this in Welwyn Hatfield Borough Council v Secretary of State for Communities and Local Government [2011] UKSC 15. If you actively misled the LPA about what was being built or used, you cannot later rely on the passage of time.

Listed buildings are entirely outside this framework. There is no immunity period for listed building enforcement. A Listed Building Enforcement Notice can be served at any time, no matter how many decades ago the unauthorised works were done. This applies to any works affecting the character of a listed building carried out without listed building consent, including works of maintenance that would be ordinary in an unlisted property.

Certificates of Lawful Existing Use or Development (CLEUD)

Once the relevant immunity period has passed, the owner can apply to the LPA for a Certificate of Lawful Existing Use or Development (CLEUD) under Section 191 of the TCPA 1990. This certificate formally confirms that the development or use is now lawful. It does not retrospectively approve the planning breach — it confirms that enforcement is no longer possible.

A CLEUD is extremely important for mortgage lenders and conveyancers. Without it, a buyer's solicitor receiving replies to the Commercial Property Standard Enquiries (CPSE) or the Seller's Property Information Form (SPIF) will flag unauthorised works as a risk that may prevent lending.

Enforcement Tools Available to LPAs

Where the LPA does decide to act, it has several enforcement mechanisms. An Enforcement Notice under Section 172 must specify the alleged breach, the steps required to remedy it, and a compliance period of at least 28 days. The recipient has a right of appeal to the Planning Inspectorate under Section 174. A Stop Notice or Temporary Stop Notice (Section 171E) can halt works currently in progress — this takes immediate effect. A Breach of Condition Notice under Section 187A addresses non-compliance with a planning condition specifically; unlike the Enforcement Notice route, breach of a BCN is a criminal offence without the need for a further notice.

What to Do If You Are in Breach

If you discover that works have been carried out without planning permission — whether on a property you own or one you are considering purchasing — the first step is to obtain independent planning advice. Do not start further works. Consider applying for retrospective planning permission under Section 73A of the TCPA 1990, which allows an application for permission to be made after development has already been carried out. Consider whether the immunity period has run, and if so apply for a CLEUD.

On any property sale, enquiries will specifically ask about the planning history of the property and any known breaches. Incorrect or incomplete answers can constitute misrepresentation under the Misrepresentation Act 1967 or the Consumer Protection from Unfair Trading Regulations 2008, with significant legal consequences.

RCB Design & Build always confirms the planning position and compliance pathway — including whether proposed works require planning permission, building regulations approval, or both — before starting any project.

Batch 26 Summary

Posts 131–135 | Created 2026-07-20 | RCB Design & Build blog content

Post 131: What a Structural Engineer Produces
Post 132: Damp, Mould and Condensation in Old London Homes
Post 133: Material Change of Use Explained
Post 134: Retention in Construction Contracts
Post 135: Planning Enforcement in London