Do I need planning permission for an HMO? Article 4 explained

This one is for anyone thinking about buying a house to run as an HMO, or converting a buy-to-let they already own. Whether you need planning permission depends almost entirely on one thing: whether the property sits inside an Article 4 area. Get this wrong and you can be ordered to undo the whole conversion, so check it before you exchange, not after.

The short answer

Turning an ordinary house into a small HMO (3 to 6 unrelated sharers) normally needs no planning application. It is permitted development.
If the council has made an Article 4 direction covering the property, that right is switched off and you need full planning permission.
An HMO for 7 or more people always needs planning permission, everywhere, Article 4 or not.

Everything else in this guide is the detail behind those three lines.

The three planning boxes an HMO can sit in

Planning law sorts residential property into "use classes". For HMOs, three matter:

Use class	What it covers	Planning permission to convert into it?
C3 dwellinghouse	A normal home: a family, a couple, or up to 6 people living as a single household	Not applicable, this is the starting point
C4 small HMO	3 to 6 unrelated residents sharing facilities (kitchen, bathroom) as their main home	Normally no (permitted development), unless Article 4 applies
Sui generis large HMO	More than 6 residents	Always yes, everywhere

The C4 definition comes from the Town and Country Planning (Use Classes) (Amendment) (England) Order 2010: use of a dwellinghouse as an HMO by not more than six residents. Anything above six falls outside every use class ("sui generis"), so changing to it always needs a planning application. There is no permitted development route to a 7-bed HMO.

The normal rule: C3 to C4 is permitted development

Class L of Part 3, Schedule 2 of the General Permitted Development Order 2015 grants automatic planning permission for a change of use from C3 to C4, and back again. So in most of England, buying a 3-bed terrace and letting it to four unrelated sharers involves no planning application at all. You may still need building regulations sign-off for physical works, and possibly a licence (more below), but the planning side is automatic. One caveat: Class L covers a straight swap of use, not splitting one building into two or more separate homes or HMOs.

What an Article 4 direction does

An Article 4 direction is a legal tool that lets a council switch off specific permitted development rights in a defined area. Where a direction targets Class L, the automatic C3-to-C4 right disappears and you must apply for full planning permission like any other development. The mechanics are set out in the government's planning guidance, When is permission required?

Two things an Article 4 direction is not:

It is not a ban. Councils can and do grant permission for HMOs in Article 4 areas. But many pair the direction with policies limiting HMO density (for example, refusing where too many nearby properties are already HMOs), so approval is far from guaranteed.
It is not retrospective. If the property was already lawfully in C4 use before the direction took effect, that use is established. This is why proving an existing HMO's history matters so much when you buy one.

Most HMO directions are "non-immediate": the council announces the direction at least 12 months before it bites, because giving a year's notice removes the council's liability to compensate owners for the withdrawn right. The practical effect for investors: there is usually a publicised window between announcement and commencement, and a genuine change of use completed before the start date preserves your position. Cutting it fine is risky, because you would need evidence the C4 use had actually begun (tenants in occupation), not just an intention.

Coverage is growing fast

Article 4 HMO directions used to be a student-city thing. Not any more. Recent borough-wide examples:

Walsall: in force from 1 October 2025 (Walsall Council).
Oldham: in force from 1 January 2026, confirmed by the council on 15 December 2025 (Oldham Council).
Birmingham has a city-wide HMO direction, recorded on the national planning data platform.

In London, boroughs including Ealing, Croydon, Tower Hamlets and Waltham Forest have HMO directions covering some or all of their area. There is no single official count, and industry trackers in 2026 put the figure at more than 20 of the 33 London boroughs, but treat any list as out of date the day it is published. Directions are being made every few months, which is exactly why you check the specific postcode, not a map from last year.

How to check before you buy

Do this before you offer, and again before exchange:

Run our free Area Check tool. Put in the postcode and it queries the government's planning.data.gov.uk Article 4 datasets for directions covering that location. Takes about ten seconds.
Confirm on the council's own planning pages. The national dataset relies on councils publishing their data, and not all do promptly. The council site is authoritative and will also show directions announced but not yet started.
Ask the council's planning team in writing if it is marginal. Boundaries can run down the middle of a street.

If the area is under Article 4, price the deal accordingly: a planning application costs money and months, refusal is a real possibility in high-density HMO wards, and your exit value changes if the next buyer cannot assume HMO use.

What happens if you convert anyway

Convert to a C4 HMO in an Article 4 area without permission and you are in breach of planning control. The council can serve an enforcement notice requiring you to return the property to a single dwelling, and ignoring one is a criminal offence with an unlimited fine. You get no compensation for wasted conversion costs or lost rent, and the notice sits on the property's record, strangling resale value.

Waiting out the enforcement clock is not a plan. An unauthorised change of use to an HMO has long been subject to a 10-year enforcement window (the old "4 year rule" never covered it; that shorter limit applied to building works and changes of use to a single dwellinghouse). And for breaches occurring on or after 25 April 2024, the Levelling-up and Regeneration Act 2023 changes apply a single 10-year limit to effectively all breaches anyway. A decade of exposure on a property you may want to remortgage or sell is not a strategy.

Article 4 and HMO licensing are different regimes

Planning permission and HMO licensing are separate legal systems, run by separate council departments, and both can apply to the same property:

Planning (this guide) controls the change of use of the building.
Licensing, under the Housing Act 2004, controls how the HMO is managed and its standards. Mandatory licensing applies to HMOs with 5 or more people from 2 or more households anywhere in England, per the government's licensing guidance, and many councils run additional licensing schemes catching smaller HMOs too.

Holding a licence does not grant planning permission, and having planning permission does not exempt you from licensing. A 5-bed HMO in an Article 4 area needs both. Our HMO licensing guide covers the licensing half in full.

Mistakes people make

Checking licensing but not planning. The licence application form will not tell you the property needs planning permission.
Relying on the agent's word that "the street is full of HMOs". Those may all predate the direction. Yours would not.
Assuming a 6-bed is the same as a 7-bed. Six sharers can be permitted development. Seven is sui generis and always needs a planning application.
Buying "an HMO" with no paperwork. In an Article 4 area, the seller should evidence lawful C4 use from before the direction, ideally with a Lawful Development Certificate. No evidence, big discount or walk away.
Missing a direction that has been announced but not started. The 12-month notice period means the risk is visible a year out, if you look.

Thirty seconds on the Area Check tool and ten minutes on the council's planning pages will tell you which side of the line your deal sits on. Do it before the money moves.

Sources: legislation.gov.uk, GPDO 2015 Schedule 2 Part 3 Class L · legislation.gov.uk, Use Classes (Amendment) (England) Order 2010 · gov.uk, When is permission required? · Oldham Council, Article 4 Direction · Walsall Council, HMO Article 4 Direction · planning.data.gov.uk, Article 4 direction area dataset · gov.uk, Enforcement changes under the Levelling Up and Regeneration Act · gov.uk, HMO and residential property licensing reform guidance

Education, not financial advice. For mortgage advice, speak to an FCA-authorised broker.