HMO Change of Use Applications: When Converting a Property Needs More Than a Licence

Converting an ordinary family home into a shared HMO is one of the most common ways London landlords increase rental yield — but the conversion itself can trigger a legal process entirely separate from the HMO licence application. Landlords who focus only on licensing sometimes discover, partway through fitting out bedrooms and installing extra locks, that the local planning department takes an entirely separate view on whether the conversion is allowed at all. Understanding when a change of use application is needed, on top of licensing, avoids a costly surprise partway through a project.

What "change of use" actually means

Under planning law, different uses of a building fall into different use classes. An ordinary dwelling occupied by a single household is use class C3. A small HMO, broadly meaning a property let to between three and six unrelated occupants, sits in a distinct category, use class C4. Moving a property from C3 to C4 is, in planning terms, a change of use — a specific legal event that planning law treats entirely separately from the HMO licensing process run by the council's housing team, even though both are triggered by the same underlying decision to convert the property.

These two systems don't communicate with each other automatically. A council's licensing team assesses management standards, fire safety, and room sizes; a planning department, often based in a different part of the council with entirely different staff, assesses whether that particular use of that particular building is permitted at all. It's entirely possible to hold a valid HMO licence for a property that is, technically, in breach of planning control, or to have full planning permission for a use that hasn't yet been licensed.

Permitted development — usually, but not always automatic

In most of England, a C3-to-C4 conversion falls under permitted development rights, meaning the change of use itself doesn't require a specific planning application — the property simply moves categories without the landlord needing to apply for anything on the planning side. This is the default position, and it's why many landlords reasonably assume that converting a family house into a small HMO is a licensing-only exercise.

However, a significant number of London boroughs have removed this right through what's known as an Article 4 Direction. Where an Article 4 Direction applies to a street or area, the permitted development right for C3-to-C4 conversion is withdrawn, and full planning permission is required for exactly the same conversion that would be automatic a few streets away in a borough without one. Article 4 status is often set at a granular, sometimes street-by-street level, so checking the borough's general policy isn't always enough — the specific address matters.

Larger HMOs always need planning permission

The permitted development route only ever applied to small HMOs. For HMOs with seven or more occupants, described in planning terms as a "sui generis" use, planning permission is required everywhere in London regardless of Article 4 status. There is no permitted development route for HMOs at this scale, so landlords planning a larger shared house — a former hotel or care home conversion, for example — should assume a full planning application is needed from the outset, not just a licence application.

This distinction catches out landlords scaling up from a small, licensed HMO to a larger one on the same site. Adding rooms to push occupancy from six to seven or more doesn't just change which licence category applies — it moves the property into a use class that always requires planning permission, even in a borough with no Article 4 Direction at all.

Building regulations are a third, separate process

Beyond planning, the physical conversion work itself — adding partition walls, converting reception rooms into bedrooms, installing additional bathrooms or kitchens — will often separately require Building Regulations approval. This covers matters like fire safety, means of escape in the event of a fire, and sound insulation between newly created rooms, and it sits alongside planning and licensing as a genuinely distinct approval process, administered again by a different function (building control) with its own application and inspection route.

A conversion can be planning-compliant and licensing-compliant and still fall short of building regulations requirements if the physical works weren't signed off properly. This matters at resale too — a buyer's solicitor or surveyor will typically ask for completion certificates for any structural conversion work, and gaps here can complicate a sale long after the licence itself has been granted without issue.

What commonly goes wrong

The most frequent mistake is landlords treating the HMO licence as the only approval needed, because it's the most visible requirement and the one most commonly discussed among landlords. A landlord converts a property, submits a licence application, and only discovers an Article 4 Direction applied to their street when the council's licensing team flags a planning enforcement risk during the inspection — by which point walls have already been built and tenants may already be in occupation. Retrospective planning applications are possible but are not guaranteed to succeed, and enforcement action is a real risk where a change of use has taken place without permission where it was required.

Sequencing matters

Because these are genuinely separate processes with separate application routes, decision-makers, and timescales, the sensible order is to establish the planning position first wherever there's any doubt about Article 4 status, before committing to conversion works or to a licensing timeline that assumes the change of use is unproblematic. Checking the borough's planning portal or contacting the planning department directly, ideally before exchanging on a purchase intended for HMO use, costs little and avoids a scenario where a licence has been granted for a use that planning law doesn't currently permit.

We focus on licensing — but we'll flag what else you need

Our service handles your HMO licence application specifically — Additional HMO Licence applications are a fixed £300+VAT, and Mandatory HMO Licence applications are £500+VAT. As part of reviewing your property, we'll flag if your borough's Article 4 status or the scale of your proposed conversion suggests a separate planning or building regulations process is needed, so you're not caught out mid-project, and can be pointed toward the right specialist for that separate application.