Class C4 HMO Compliance Essentials: Planning, Licensing, Safety and Regulations
02, Oct, 2026
A house might look ideal for an HMO until the compliance questions begin. How many people will live there? Does the property need planning permission? Does an Article 4 Direction apply? Are the bedrooms large enough? What fire safety work is needed?
These questions matter before walls are moved or bedrooms are added. Understanding class C4 HMO requirements early helps landlords avoid expensive changes later. Planning, licensing, safety and the physical condition of the property all need to work together before tenants move in.
What Is a Class C4 HMO?
Class C4 covers the use of a dwellinghouse by no more than six residents as a house in multiple occupation. In simple terms, it generally applies to a small HMO where several unrelated people live together and share facilities.
The important number is six. A property planned for seven or more residents falls outside the C4 use class and usually has a different planning position. This means landlords need to think about the number of occupants before deciding how many bedrooms to create.
Does a C4 HMO Need Planning Permission?
Not always, but the answer depends on the property's location. A change from a normal dwellinghouse use to a small C4 HMO has historically benefited from permitted development rights in areas without an Article 4 Direction. A council can remove those rights, meaning planning permission is required for the change.
Merton is a good example for South West London landlords. The council has removed permitted development rights for C3 to C4 conversions across the whole borough. The latest controls covering the remaining 13 wards started on 24 March 2026. A new small HMO conversion in Merton therefore requires planning permission.
Planning Permission and HMO Licensing Are Different
Planning permission deals with whether the proposed use or development is allowed. HMO licensing deals with whether the property meets the requirements for operating as a licensable HMO. GOV.UK states that mandatory licensing applies to HMOs rented to five or more people from more than one household who share facilities. Smaller HMOs might also need a licence where the local council has additional licensing rules.
Merton also makes this distinction clear. Its planning guidance states that HMO licensing is separate from planning permission.
What Safety Requirements Apply to a C4 HMO?
The property needs suitable fire precautions, safe escape routes and working smoke alarms. Electrical systems, gas appliances where present, heating, kitchens and bathrooms also need to meet the relevant requirements.
The exact work depends on the property. A house with an older electrical system might need an upgrade. Another property might need changes to doors, escape routes or fire detection. This is why safety should be considered when the layout is planned, rather than after the bedrooms have already been built.
How Big Do C4 HMO Bedrooms Need to Be?
Bedroom size is another area where a planned layout might run into problems. For licensed HMOs in England, the national minimum sleeping room size is 6.51m² for one person aged over 10 and 10.22m² for two people aged over 10. A room used by one child under 10 has a minimum of 4.64m².
Local councils might set additional standards, so these figures should not automatically become the target for every property. For landlords, the lesson is simple. Do not divide the house into as many bedrooms as possible before checking the relevant HMO standards.
What Happens If You Want More Than Six Residents?
Class C4 covers no more than six residents. A proposal for seven or more residents falls outside C4 and normally has a different planning classification. That change might affect the planning application, layout and other requirements for the property. If an extra bedroom is being considered, check the planned occupancy before changing the layout. One additional resident might change the planning position of the entire project.
What Building Work Does a C4 HMO Conversion Involve?
A C4 HMO conversion might involve new internal walls, additional bathrooms, kitchen changes, plumbing alterations, electrical upgrades, fire safety improvements, structural work, heating changes, and new finishes. Adding a bathroom requires suitable plumbing and drainage. Moving walls affects the room layout and sometimes the structure.
Denham Crescent provides architectural, structural, refurbishment and construction services and oversees projects from feasibility and permits through design and construction. Its structural works service also covers structural alterations, foundations and assessments of existing buildings.
What Should Landlords Check Before Starting?
Before work begins, check:
The property's current planning use.
Whether an Article 4 Direction applies.
The number of planned residents.
Whether an HMO licence is required.
Local bedroom and space standards.
Fire safety and escape arrangements.
Electrical, heating and plumbing requirements.
Any structural changes needed.
What is included in the building quotation.
This checklist helps identify problems before construction starts rather than after money has already been spent.
Why the Right Builder Matters for a C4 HMO
Denham Crescent has experience with complex property refurbishment and multi-trade work. In Mitcham, one refurbishment included plumbing, electrical work, built-in wardrobes, a driveway, a new kitchen and a further extension. The client, Mohsin Chughtai, praised the quality of the work and service.
Another client, Theran Bhatia, said Denham had renovated and extended two of his properties and also maintained his other properties. He praised the finish, cost control and the team's response to problems.
Class C4 HMO Compliance Checklist
Before converting a property, make sure you have checked:
Planning use and Article 4 restrictions
C3 to C4 change of use
HMO licensing requirements
Number of residents
Bedroom sizes
Fire safety
Escape routes
Kitchen and bathroom facilities
Electrical and gas safety
Structural requirements
Building and refurbishment work
Getting these points right early gives landlords a clearer picture of what the property needs before construction begins.
Plan Your Class C4 HMO Before Construction Starts
Class C4 HMO compliance involves more than changing the use of a property. Planning permission, licensing, room sizes, safety measures and the actual building work all need to fit together.
For landlords planning a class C4 HMO conversion in South West London, Denham Crescent provides architectural, structural, refurbishment and construction services to help manage the building work from the early planning stages through to completion.
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