What Is an HMO? Meaning and Rules

HMO meaning: people, households and shared facilities

GOV.UK sets out the everyday test. A property is an HMO when at least 3 people who are not from 1 household rent it. They also share toilet, bathroom or kitchen facilities.

The Housing Act 2004 gives the legal tests in section 254. The main one is the standard test. A building, or part of one, meets it when these main conditions apply:

1. Not self-contained. The living space is not a self-contained flat or flats.
2. More than one household. The people living there do not form a single household.
3. Only or main home. They live there as their only or main residence.
4. Rent. Rent is paid for at least one of the people living there.
5. Shared amenities. Two or more households share a toilet, washing facilities or a kitchen, or the home lacks one of them.

A household is one family. Section 258 counts a couple as one household, whether married, civil partners or living together as if they were a married couple or civil partners. Close relatives also count, such as parents, children, brothers, sisters, aunts, uncles and cousins.

So 3 unrelated friends sharing a kitchen form an HMO. A family of five does not. Section 259 treats a student's term-time home as their main residence, so a student house can be an HMO.

Section 254 also covers some converted buildings, and some badly converted blocks of flats under section 257. That applies where the conversion did not meet building standards, still does not, and fewer than two-thirds of the flats are owner-occupied.

Once you know a house is an HMO, the next question is its planning class.

Small C4 HMOs vs large sui generis HMOs

Planning law sorts HMOs by size, not by the licence. In England and Wales, the Use Classes Order puts a small HMO in Class C4. Its wording is the use of a house "by not more than six residents" as an HMO.

The Planning Portal describes C4 as small shared houses with 3 to 6 unrelated residents. An HMO with more than 6 residents falls outside every use class. Planners call that sui generis, a use of its own kind.

The licence rules use a different number. A house of 5 or 6 people is C4 for planning, yet it can still need a mandatory licence. Check both sets of rules, not one.

A family house is Class C3. That matters, because the move from C3 to C4 has its own planning route, set out below. If you are buying, ask the council for the current use class before you exchange.

HMO licence types: mandatory, additional and selective

Licensing is run by your council's housing team, not its planners. There are three types, and a house can fall under more than one.

1. Mandatory licence. In England, an HMO needs one when 5 or more people from 2 or more households live there. This applies in every council area.
2. Additional licence. A council can widen licensing to smaller HMOs, across its whole district or part of it. Section 56 of the Housing Act 2004 gives it that power.
3. Selective licence. A council can require licences for privately rented houses in a set area. The area must meet tests such as low housing demand or persistent anti-social behaviour.

GOV.UK says a licence lasts for a maximum of 5 years, and you must renew it before it expires. Each council sets its own fee.

Licences come with duties. GOV.UK lists sending the council a gas safety certificate every year, and installing and maintaining smoke alarms. You must also show electrical safety certificates when asked.

Our guide to HMO licences and regulations covers the application, the inspection and the conditions in full.

HMO planning permission and Article 4 directions

In England, changing a family house (C3) into a small HMO (C4) is usually permitted development. Class L of the General Permitted Development Order allows it without a planning application. It also allows the change back from C4 to C3.

Class L has a limit. It does not allow one house to become two or more separate homes. A large HMO for more than 6 residents is sui generis, so it always needs planning permission.

An Article 4 direction changes the small HMO route. GOV.UK explains that it lets a council withdraw set permitted development rights in an area. Work covered by a direction needs a planning application instead.

Some councils use Article 4 directions to control new small HMOs, so check before you buy. Your council's planning team is the first point of contact. It can tell you whether a direction covers the street.

Our guide to HMO planning permission explains the applications, and our Article 4 guide for HMOs covers how directions work in London.

HMO room sizes and fire safety basics

Room sizes are licence conditions in England. Every licensed HMO must meet them, including those under additional licensing.

A room smaller than 4.64 m² cannot be used for sleeping. Floor area under a ceiling lower than 1.5 m does not count towards the size. That rule matters in loft rooms with sloping ceilings.

Fire safety is a duty for every HMO manager. The management regulations for England require the means of escape to be kept clear and in good repair. Fire alarms and any firefighting equipment must be kept in good working order.

Notices showing the escape route must be displayed, unless the HMO has 4 or fewer occupiers. Your council can set further conditions on the licence.

Our guide to HMO conversion standards covers kitchens, bathrooms, fire doors and layouts in more depth.

Unsure about the first four lines? Our free route check answers them for the address you send.

Before you buy or convert a house as an HMO

Three numbers decide most of the rules. Seven residents makes the house sui generis. Five residents triggers a mandatory licence. An Article 4 direction can stop a small HMO without permission.

So work out three things for the house first: the planning route, the licence it needs, and how many rooms pass the size rules. Together they decide how many rooms you can let.

We have been in the market for 10 years, since 2016. One team draws the layout, secures the consent and builds the house, so nothing is lost between consultants. Our Development Director, Rob Barton, is a former housebuilding managing director.

Send us the address for a free HMO route check. You get the planning class, any Article 4 restriction and the licences your council runs there, so you know the route before you commit.