HMO minimum room size standards
HMO minimum room size standards are the legally required lower limits for sleeping rooms in licensed Houses in Multiple Occupation in England. They are set by the Licensing of Houses in Multiple Occupation (Mandatory Conditions of Licences) (England) Regulations 2018, which came into force on 1 October 2018 alongside the extension of mandatory licensing. A room that does not meet the minimum for its intended occupancy cannot be used as sleeping accommodation, and the licence will reflect that restriction. Room size compliance is a mandatory condition of every HMO licence, and councils check measurements during inspection.
The minimum sizes
The national minimums for rooms used as sleeping accommodation are:
6.51 m² for one person aged ten or over
10.22 m² for two people aged ten or over sharing a room
4.64 m² for one child under ten
No room with a floor area below 4.64 m² may be used as sleeping accommodation at all. Landlords also have a separate duty to notify their local housing authority of any room in the HMO with a floor area below 4.64 m², even where it is not used for sleeping. These are national statutory minimums, local authorities may impose higher standards through licence conditions, and commonly do. Always confirm the applicable local standard directly with the council before finalising occupancy plans.
The standards apply to any HMO that requires licensing, whether under the national mandatory scheme or a local additional scheme.
How to measure correctly
Floor area is measured wall to wall at floor level, but only where the ceiling height is greater than 1.5 metres. Any part of a room where the ceiling is at or below 1.5 metres, including areas under eaves, sloping rooflines, or loft conversions, is excluded from the usable floor area calculation entirely. For a rectangular room with a flat ceiling this is straightforward: length multiplied by width. For rooms with sloping ceilings, landlords must first establish the line at which the ceiling drops to 1.5 metres and calculate only the area within that line.
En-suite bathrooms and shower rooms attached to a bedroom are not included in the sleeping room floor area measurement. A room measuring 12 m² with an attached 3 m² en-suite gives a sleeping room area of 9 m², which meets the single-person minimum of 6.51 m² but falls short of the two-person threshold of 10.22 m². This is one of the most common miscalculations we see among landlords converting properties for the first time.
Built-in wardrobes, on the other hand, are generally included in the floor area measurement. Confirm the approach with your local authority before submitting plans, as council inspectors can interpret borderline cases differently.
Local authority discretion
The 2018 Regulations set the national floor. Local authorities are required to impose licence conditions specifying the maximum number of persons permitted per room, and they have discretion to set higher minimum sizes through those conditions. Councils in London in particular frequently apply local standards that exceed the national minimums, some requiring 8 m² or more for a single-occupancy room. Purchasing or converting an HMO without checking the local standards can result in a compliance shortfall that is expensive to remedy after the fact.
Consequences of breach
Letting a room below the permitted size is a breach of the HMO licence, which is a criminal offence under the Housing Act 2004. Councils can impose civil penalties of up to £30,000 and revoke the licence. Tenants may apply to the First-tier Tribunal for a rent repayment order of up to 24 months' rent under the Renters' Rights Act 2025, which is now in force as of 1 May 2026. A non-compliant room also reduces the lettable capacity of the property, directly cutting rental income until the issue is resolved, either by reconfiguration, de-occupation of the room, or successful renegotiation of the licence condition.
From working with self-managing landlords across the UK, we find that room size errors most often arise at the point of purchase rather than conversion. Many older HMOs were built before the 2018 standards and contain rooms that were previously let legally but no longer meet the minimum for their occupancy level. Use the August HMO calculator to model room-by-room income against occupancy, so you can see exactly how room sizes affect net yield before committing to a conversion. For a full treatment of the licensing application process and what councils inspect, see our mandatory HMO licensing guide.
Frequently asked questions
Do HMO room size standards apply to unlicensed HMOs?
The minimum sizes introduced by the 2018 Regulations are mandatory conditions of HMO licences. An HMO that does not require licensing is not subject to these specific standards. However, the Housing Health and Safety Rating System applies to all rented properties regardless of licensing status, and overcrowding is one of the 29 assessed hazards, so very small rooms can still attract enforcement action even in unlicensed properties.
What happens if my council sets a higher standard than the national minimum?
The council's local standard prevails. A room that meets the national minimum of 6.51 m² for a single occupant may still be refused at licence stage if the council's own HMO standards require, say, 8 m². These local standards are set through licence conditions and can vary significantly. Check with the local housing authority before submitting plans or purchasing a property with the intention of converting it.
Can a room below the minimum be used for storage instead?
Yes, a room below the minimum for sleeping cannot be used as sleeping accommodation, but there is no prohibition on using it as storage, a study, or communal space. The constraint is on its use for sleeping, not its existence in the property. Repurposing undersized rooms as communal areas is a common practical solution.
