Setting Up an HMO: Planning, Conversion, and Ground 4A

What changed under the Renters’ Rights Act 2025

Section 21 abolished. Fixed-term assured tenancies abolished. Ground 8 threshold raised to 3 months. Information Sheet required for every tenancy by 31 May 2026. Read the full guide.

Setting up a House in Multiple Occupation involves three regulatory streams running in parallel: planning permission, building regulations, and HMO licensing. Each has its own approval process and consequences. This page sets out the planning use classes (C3, C4, sui generis), Article 4 directions, building regulations Approved Documents, realistic conversion cost estimates, insurance requirements, and the Ground 4A possession ground for student HMOs introduced by the Renters’ Rights Act 2025 — including the advance-notice condition that catches out landlords who don’t plan ahead.

Three regulatory streams to think about

Setting up an HMO involves three regulatory streams that operate in parallel. Each has its own approval process, its own timescales, and its own consequences for getting it wrong. Treating them as one undifferentiated mass is the most common reason HMO setups overrun budget and timeline.

Planning permission determines whether the property can lawfully be used as an HMO at all. The starting question is whether permitted development rights apply or whether full planning permission is required.

Building regulations determine whether the physical works to convert or refurbish the property meet construction standards — fire compartmentation, escape routes, electrical safety, energy efficiency, structural integrity.

HMO licensing determines whether the property can lawfully be let to multiple occupiers under the Housing Act 2004 — covered in detail in our HMO licensing guide.

A property can have planning permission and not be safe for occupation. It can satisfy building regulations but not be licensable as an HMO. It can be licensed as an HMO but lack planning permission. All three streams must be properly addressed, and none substitutes for the others.

Planning permission: C3, C4, and sui generis

The planning use class system distinguishes three relevant categories for residential property:

C3 (dwelling house) covers a property used as a single dwelling by a person, persons living together as a family, or up to six people living together as a single household. A typical family home is C3.

C4 (small HMO) covers an HMO used by between three and six unrelated occupiers from two or more households who share basic amenities. A four- or five-bedroom property let to sharers is typically C4.

Sui generis (large HMO) covers HMOs with seven or more occupiers. There is no use class for these — they are sui generis (“of its own kind”) and always require full planning permission for any change to or from this use.

Permitted development rights

In most areas of England, change of use from C3 to C4 (small HMO) is permitted development, meaning a landlord can convert a single-family home into a small HMO without applying for planning permission. This right was introduced from 1 October 2010 and is granted under the Town and Country Planning (General Permitted Development) (England) Order 2015.

Two important limits. First, the right does not extend to changes of use to sui generis large HMO — those always require full planning permission. Second, local authorities can remove the C3-to-C4 permitted development right in designated areas through an Article 4 direction. It is also worth knowing the right runs one way in practice: changing a C4 HMO back to C3 does not need permission, but converting back to C4 again afterwards does.

Article 4 directions

Article 4 directions are orders made by a local planning authority that remove specified permitted development rights in defined geographic areas. They are most commonly used to remove the C3-to-C4 conversion right in areas with high HMO concentrations, where the character of the area is judged to be at risk from further HMO growth.

Article 4 directions covering HMO conversions are typical in:

• University towns and cities — many wards in Leeds, Newcastle, Nottingham, Manchester, Bristol, Brighton, and other cities and towns with significant student populations have Article 4 directions covering some or all of their HMO-heavy areas.
• Inner-city areas with established high HMO concentrations.
• Areas where the local plan identifies HMO over-concentration as a planning issue.

In an Article 4 area, any change of use from C3 to C4 requires full planning permission, and the local authority can refuse it where, in its planning judgment, the change would harm the character of the area or add to existing HMO over-concentration.

Always check the Article 4 position before committing to an HMO conversion. Local planning authorities publish Article 4 area maps and HMO planning policy on their websites — check the specific address, not just the general area, since directions can be drawn ward-by-ward or street-by-street. If you are buying a property to convert, make this check before exchange of contracts. A property in a busy Article 4 area where planning permission is unlikely to be granted is not a viable HMO project, regardless of the property’s physical suitability.

When planning permission is required

In summary, planning permission is required for HMO use when:

• The HMO will have seven or more occupiers (sui generis change of use).
• The property is in an Article 4 area, and the conversion is from C3 to C4.
• The HMO involves external alterations requiring planning permission (extensions, dormer windows, change to the front elevation in a conservation area).
• The property is in a conservation area or is listed, where additional planning controls apply.

Outside these cases, change to small HMO (C4) is usually permitted development and no planning application is required. HMO licensing requirements are separate and still apply regardless of the planning position.

Building regulations

Building regulations control the construction quality of the works to set up the HMO. The relevant Approved Documents are issued by government and updated periodically. The most relevant for HMO conversions are:

Approved Document B (Fire Safety) — the most demanding for HMOs. Sets out requirements for fire compartmentation between rooms and floors, fire-resisting construction of walls and doors, escape route design, and detection and alarm systems. Approved Document B drives most of the fire door, protected escape route, and structural fire resistance requirements behind typical HMO conversion costs.

Approved Document P (Electrical Safety) — covers electrical installations. New consumer units, new circuits, and new sockets in kitchens and bathrooms must be installed by competent persons and certified.

Approved Document G (Hygiene) — covers water supply, sanitation, and hot water provision. Relevant where bathrooms, en-suites, or kitchens are added to a converting property.

Approved Document L (Energy Efficiency) — covers insulation, glazing, and energy performance. Relevant where significant works affect the property’s thermal performance.

Approved Document M (Access) — covers accessibility. Relevant where significant works affect access to or within the property.

Building regulations approval is a separate process from planning permission. The conversion works require either a full plans submission to the local authority’s building control department, a building notice (suitable for smaller works), or use of a registered building control approver. The works are inspected at key stages and a completion certificate issued at the end.

Operating an HMO without building regulations approval for required works is unlawful. Local authorities can require the works to be undone (taking out non-compliant fire doors, removing additional bathrooms) or upgraded to a compliant standard. Retrospective compliance routinely costs more, and causes more disruption, than doing the works correctly the first time.

Realistic conversion costs

Converting a four-bedroom family home into a five- or six-bedroom HMO involves substantial works. The figures below are market estimates gathered from typical landlord and contractor experience — not statutory fees — and vary by location, property condition, and finish standard. Always get at least three quotes from contractors with HMO experience, and check your local authority’s HMO standards document for what is required in your specific case before budgeting.

Fire safety upgrade. Replacement of internal doors with FD30 fire doors and frames including intumescent strips and self-closers; mains-wired interlinked smoke alarms throughout with a heat detector in the kitchen; emergency lighting on protected escape routes where relevant; closing off any non-compliant openings between rooms and the escape route. Typical estimate: £6,000–£12,000.

Additional bathroom or en-suite installation. If the property has fewer bathrooms than the local standard requires, an additional bathroom must be added. A loft conversion en-suite, ground-floor shower room, or new first-floor bathroom typically costs £4,000–£10,000 each.

Kitchen reconfiguration. Many family kitchens are inadequate for five or six occupiers. Larger units, an additional cooker, additional refrigeration, additional worktop space — typical estimate £3,000–£8,000.

Electrical upgrade. Old consumer units and circuits may not support HMO loads. A new consumer unit, additional circuits, additional sockets in bedrooms, and EICR certification — typical estimate £2,000–£5,000.

Bedroom alterations. Some rooms may need partition adjustment to meet minimum sizes; others may need built-in storage to make small rooms practical. £1,000–£4,000.

Energy efficiency works. Bringing the property up to the current legal minimum (EPC E) or further, ahead of tightening standards — see below. Insulation, draught-proofing, glazing, and heating efficiency work. £2,000–£10,000 depending on the existing condition.

Furniture and fittings. Beds, mattresses, desks, chairs, wardrobes, kitchenware, white goods. For a five-bedroom HMO furnished to a reasonable standard, £4,000–£8,000.

Professional fees. Architect or designer (if substantial layout changes), planning consultant (if planning permission required), fire risk assessor, inventory clerk, lettings agent set-up. £1,500–£5,000.

Total illustrative range for a four-bedroom-to-five-bedroom HMO conversion: roughly £20,000–£40,000. Larger conversions (bedrooms added through a loft conversion, complete refurbishment of an older property) commonly run £40,000–£75,000. These are estimates for budgeting purposes only — check current costs with contractors and your council before committing.

Energy efficiency standards are tightening

EPC E is currently the legal minimum energy rating for private rented tenancies in England. The government’s Warm Homes Plan (published January 2026) sets out a target for privately rented homes to reach EPC C — or an equivalent multi-metric standard — by 1 October 2030, alongside a proposed cap on required spend and an exemption route where the cap is reached without hitting the target. Landlords setting up an HMO now should budget for the direction of travel, not just the current minimum — check gov.uk for the latest confirmed regulations before finalising a specification.

Insurance

Standard residential building insurance does not cover HMO use. A landlord operating an HMO under residential insurance is uninsured for HMO-related loss — including fires, water damage caused by tenants, public liability claims, and legal expense claims arising from HMO operation.

A specialist HMO policy is essential. Specialist insurers underwrite HMO risk and typically provide:

• Buildings cover that contemplates multiple-occupier use.
• Contents cover for landlord-supplied furnishings (essential for furnished HMOs).
• Public liability cover, commonly with a £2 million minimum and £5–£10 million increasingly offered.
• Loss of rent cover for periods following insured events.
• Legal expenses cover for landlord-tenant disputes.
• Malicious damage by tenants — historically excluded from standard buy-to-let policies but increasingly included in specialist HMO policies.

Premiums vary by insurer, property, and cover level — get quotes from specialist HMO insurers rather than relying on a general estimate, and confirm the policy is written for HMO use specifically before you complete on cover.

Ground 4A: the mandatory ground for student HMOs

The Renters’ Rights Act 2025 introduced Ground 4A, a mandatory possession ground for HMOs let entirely to full-time students, recoverable in line with the academic year. It sits alongside the older Ground 4, which is much narrower: Ground 4 can only be used by universities and colleges themselves, for accommodation they let to their own students, with just two weeks’ notice. Ground 4A is the ground most private HMO landlords letting to students will actually rely on.

What the HMO and student conditions require

• The property is an HMO. Under the Housing Act 2004 definition applied by the official government guidance, that means at least three tenants living there, forming more than one household, sharing a toilet, bathroom, or kitchen. Sector commentary generally treats Ground 4A as most relevant to HMOs of three or more bedrooms let to a group of sharers — check the current gov.uk grounds guidance for the definitive position on your property.
• The tenants meet the “full-time student” test. The Act defines this by reference to full-time courses provided by universities, colleges, and other listed education providers.

The two conditions landlords most often miss

• Advance written notice, given before the tenancy started. The landlord must have given the tenant written notice — before the tenancy was entered into — that they might seek possession under Ground 4A because the property is needed for a new group of students. A landlord who lets an HMO to students without giving this notice up front cannot retrofit it later in the tenancy: without the advance notice, Ground 4A is not available for that letting.
• The tenancy must not have been agreed more than six months before it started. If a landlord signs up next year’s student cohort more than six months ahead of the tenancy start date, Ground 4A cannot be used for that letting. This constrains how far in advance a landlord can safely secure next year’s tenants while preserving the ability to rely on the ground.

Timing conditions

• The possession date must fall between 1 June and 30 September in the relevant year, reflecting the normal academic-year changeover.
• Four months’ notice is required in the standard case. A transitional two-month notice period applied where the tenancy was signed before 1 May 2026 and the landlord served notice between 1 May and 31 July 2026 — a one-off easement for landlords adjusting to the new regime, not an ongoing option.

How it works in practice

A landlord letting a five-bedroom HMO to a group of students for a tenancy running roughly July to June should, at the point the tenancy is signed, give the tenants written notice that Ground 4A may be used to recover possession for the next academic year’s cohort. Ahead of the intended handover, the landlord serves a Section 8 notice specifying Ground 4A, giving at least four months’ notice, timed so the possession date falls between 1 June and 30 September. If the tenants do not leave once the notice expires, the landlord applies to court; because Ground 4A is mandatory, the court must grant possession once the ground and its conditions are proved.

What Ground 4A does not cover

Ground 4A does not help a landlord who:

• Did not give the required advance written notice before the tenancy began.
• Signed the tenancy more than six months before it started.
• Wants possession outside the 1 June–30 September window.
• Is letting a smaller property that does not meet the HMO threshold, or an HMO with non-student occupiers.
• Is a university or college seeking possession of its own accommodation — that is Ground 4, not Ground 4A.

Where Ground 4A does not apply, student-let landlords must rely on the other grounds for possession (Ground 1 for landlord occupation, Ground 1A for sale, and so on), each with its own conditions and, commonly, a 12-month protected period during which it cannot be used.

Practical roadmap for setting up an HMO

A landlord setting up a new HMO should work through the following sequence:

Pre-acquisition (or pre-conversion) due diligence. Check planning use class. Check Article 4 directions. Check the local HMO licensing scheme. Check the council’s HMO standards document. Check insurance availability and indicative premiums. Check finance — most standard residential mortgages prohibit HMO use.

Planning and design. Engage an architect or designer if substantial layout changes are needed. Engage a fire risk assessor early — the assessment shapes the works. Get at least three quotes from contractors with HMO experience.

Approvals. Submit a planning application if required. Submit a building regulations application. Submit an HMO licence application. Timescales vary by local authority — ask each department directly rather than assuming a standard turnaround, and build contingency into your project timeline.

Works. Carry out the conversion, with building control inspections at key stages, ending in a final inspection and completion certificate.

Pre-occupation compliance. EICR certificate. Gas safety certificate. EPC. Fire risk assessment recorded in writing. Inventory and schedule of condition. Insurance in place.

Occupation. Tenancy agreements signed. Statutory written statement of terms provided to each occupier. Government Information Sheet served. How to Rent guide provided. Deposit protected and prescribed information served. Landlord’s contact details displayed in the property.

A complete HMO setup, from acquisition to first occupation, commonly takes several months once approvals, works, and pre-occupation compliance are all accounted for. Compressing the timetable is risky — corners get cut, approvals are delayed, and the eventual problems cost more than the time saved.

Authoritative sources

• Town and Country Planning (General Permitted Development) (England) Order 2015 — permitted development rights.
• Planning system for houses in multiple occupation (gov.uk).
• Approved Documents (gov.uk) — building regulations technical guidance.
• Houses in multiple occupation and residential property licensing reform: guidance for local housing authorities (gov.uk).
• Renters’ Rights Act 2025.
• Renters’ Rights Act 2025, Schedule 1 — grounds for possession, including Ground 4A.
• Grounds for possession: guidance for landlords and letting agents (gov.uk).
• Domestic private rented property: minimum energy efficiency standard — landlord guidance (gov.uk).
• Your local authority’s HMO standards document and Article 4 maps.

This page is general information for landlords setting up an HMO in England, correct as at the date above — it is not legal advice on your specific property or circumstances. Check current requirements with your local authority and on gov.uk before committing to a conversion or serving a possession notice.