Article 4 Direction HMO London | C3 to C4 Planning 2026

Converting a family home (use class C3) into a small shared house of three to six unrelated occupiers (use class C4) is normally permitted development, meaning no planning application is needed. But many London boroughs have made Article 4 directions that remove this permitted development right, so a full planning application is required before you can create even a small HMO. Large HMOs of seven or more occupiers are sui generis and always need planning permission. This guide explains how Article 4 works, which boroughs operate it, and the consequences of converting without permission.

How HMO planning use classes work: C3, C4 and sui generis

Before you can understand Article 4, you need the use classes, because the whole question of whether you need planning permission for an HMO turns on them. A standard dwelling occupied by a single household, a family, falls in use class C3. A small house in multiple occupation (HMO) of between three and six unrelated occupiers sharing facilities falls in use class C4. A large HMO of seven or more unrelated occupiers does not have its own use class, it is sui generis ("of its own kind"), meaning it sits outside the standard classes. The significance is in how planning treats movement between them. The change from C3 to C4, a family home to a small HMO, is normally permitted development under national rules, so no planning application is needed by default. But the change from C3 or C4 to a sui generis large HMO is never permitted development and always requires a full planning application. So the planning question for a small HMO is entirely about whether the C3-to-C4 permitted development right is available, and that is exactly the right an Article 4 direction takes away.

What is an Article 4 direction?

An Article 4 direction is the mechanism that lets a council switch off a permitted development right in a defined area, and for HMOs it is the single most important thing a landlord must check. Permitted development rights are granted nationally, but a local planning authority can make an Article 4 direction removing a specified right across all or part of its area. For HMOs, the direction removes the right to change from C3 to C4 without planning permission. Where an Article 4 direction is in force, a landlord who wants to create a small HMO, which would be permitted development anywhere else, must instead submit a full planning application to the council and obtain permission before proceeding. The reason boroughs use Article 4 directions is to control the concentration of HMOs in residential areas, managing the impact on parking, refuse, noise and the balance of the local community. The effect for landlords is that the default national position, that a small HMO needs no planning permission, simply does not apply in large parts of London. Whether you need permission depends entirely on whether the specific area of your property is covered by an Article 4 direction, which makes checking the local position the essential first step of any HMO project. Landlords planning an HMO conversion can read more on our /for-landlords page.

Which London boroughs operate Article 4 directions for HMOs?

A large and growing number of London boroughs have made Article 4 directions covering HMO conversions, and the trend has been firmly toward more coverage, not less. Boroughs that have operated borough-wide or area-specific Article 4 directions removing the C3-to-C4 permitted development right include, among others, Barking and Dagenham, Croydon, Enfield, Newham, Redbridge, Waltham Forest, Brent, Tower Hamlets and Southwark, and the list continues to expand as more boroughs introduce directions. Some directions cover the entire borough, while others apply only to defined wards or zones where HMO pressure is greatest. Because directions are made, varied and extended by individual councils on their own timetables, the precise list and the areas covered change over time. For this reason, no published list should be treated as definitive or current. The only reliable way to know whether a specific property is affected is to check directly with the local planning authority for that borough, every London council publishes its Article 4 directions, and the planning department can confirm whether a given address is within a covered area and what the direction requires. Treating that check as the mandatory first step, before any building work is planned, avoids the expensive mistake of converting on the assumption of permitted development that has in fact been removed.

How to check a borough's Article 4 status

Because Article 4 coverage changes and varies by area within a borough, checking the status of your specific property correctly is a skill worth getting right. Start with the local planning authority's website, where Article 4 directions are published, often with maps showing exactly which areas are covered and the date the direction took effect. Read the direction itself, not just a summary, because some directions are borough-wide while others are confined to named wards or a defined boundary, and the property must be inside the covered area for the direction to bite. Note also the date: a direction generally takes effect a period after it is made (often around twelve months), which affects whether it applies to your project. If the published material is unclear, contact the council's planning department directly with the property address and ask two questions: is this address within an Article 4 direction removing C3-to-C4 permitted development, and if so what does it require. For any HMO project where the answer is uncertain or the consequences of getting it wrong are significant, a formal route exists, you can apply to the council for a lawful development certificate to confirm whether permission is required. The cost of these checks is trivial against the cost of converting unlawfully, so they belong at the very start of the project, before design, before building work, and before any tenancy commitments.

Large HMOs always need planning permission

One point cuts through all the Article 4 complexity: if your HMO will house seven or more occupiers, the Article 4 question does not even arise, because you always need planning permission. A large HMO of seven or more unrelated occupiers is sui generis, outside the standard use classes, and the change to sui generis is never permitted development anywhere in the country. So a landlord creating a large HMO must submit a full planning application regardless of whether the borough has an Article 4 direction, the direction only matters for the C3-to-C4 small-HMO threshold. This catches landlords who assume that because a small HMO might be permitted development, a slightly larger one will be too. It will not. The table below summarises which moves need planning permission and when. The pattern is straightforward: small HMOs need permission only where an Article 4 direction applies, large HMOs always need it, and the safe assumption in much of London is that permission will be required. Planning a project around the wrong assumption is one of the costliest mistakes in the HMO sector, which is why establishing the planning position first, before partitions go up or rooms are created, is non-negotiable.

Change of use	Planning permission needed?
C3 (home) to C4 (small HMO, 3–6) — no Article 4	No — permitted development by default
C3 to C4 (small HMO, 3–6) — Article 4 in force	Yes — full planning application required
C3 or C4 to large HMO (7+, sui generis)	Yes — always, anywhere in the country

Consequences of converting without permission

Converting an HMO without the planning permission you needed is not a paperwork oversight that can be quietly fixed later, it carries real enforcement risk, and understanding that risk is the final reason to check first. Where a landlord creates an HMO that required planning permission and did not obtain it, the council can take planning enforcement action. That can include an enforcement notice requiring the use to cease and, in effect, the property to revert to its lawful use, which for an HMO can mean ending tenancies and losing the rental income the conversion was meant to generate. Acting against an enforcement notice is a criminal offence. While there are time limits on enforcement and a possibility of applying for retrospective permission, neither is guaranteed, retrospective permission can be refused on exactly the grounds the Article 4 direction exists to protect. The planning position is also separate from, and additional to, HMO licensing, a property can need both planning permission and a licence, and satisfying one does not satisfy the other. The combined effect is that an unlawful HMO conversion can expose a landlord to planning enforcement, licensing penalties, and the loss of the income that justified the project. The work to establish the planning position and, where needed, to design and build the conversion to an approvable standard is modest against that exposure. We approach HMO conversions with the planning and compliance position settled first, then carry out the partitions, fire safety and refurbishment to match, so the finished HMO is lawful as well as lettable.

Frequently Asked Questions

Do I need planning permission to convert a house into an HMO in London?

It depends on the borough and the size. Changing a house (C3) into a small HMO of three to six occupiers (C4) is normally permitted development, needing no planning permission, but many London boroughs have Article 4 directions that remove this right and require a full planning application. A large HMO of seven or more occupiers is sui generis and always needs planning permission. Check the specific borough's Article 4 status before starting.

What is an Article 4 direction for HMOs?

An Article 4 direction is a measure a local planning authority can make to remove a permitted development right in a defined area. For HMOs, it removes the right to change from C3 (a home) to C4 (a small HMO) without planning permission, so a landlord in a covered area must apply for full planning permission to create even a small HMO. Boroughs use them to control the concentration of HMOs in residential areas.

Which London boroughs have Article 4 directions for HMOs?

Many do, and the number keeps growing. Boroughs that have operated Article 4 directions covering HMO conversions include Barking and Dagenham, Croydon, Enfield, Newham, Redbridge, Waltham Forest, Brent, Tower Hamlets and Southwark, among others. Some cover the whole borough, others only defined wards. Because directions change over time, the only reliable check is to confirm the current position directly with the relevant borough's planning department for your specific address.

Does a large HMO always need planning permission?

Yes. A large HMO of seven or more unrelated occupiers is sui generis, outside the standard use classes, and the change to sui generis is never permitted development anywhere in the country. A landlord creating a large HMO must submit a full planning application regardless of whether the borough has an Article 4 direction. Article 4 only affects the small-HMO (C3-to-C4) threshold.

What happens if I convert an HMO without planning permission?

The council can take planning enforcement action, including an enforcement notice requiring the use to cease, which can mean ending tenancies and losing rental income. Acting against an enforcement notice is a criminal offence. Retrospective permission can be applied for but is not guaranteed and can be refused. Planning is also separate from HMO licensing, so an unlawful conversion can expose you to both planning enforcement and licensing penalties.

Article 4 Directions and HMO Planning in London (2026)