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Cardiff Council

Houses in multiple occupancy

​This information refers to HMOs within the Planning system. View information on HMO Licensing​​​​​​​​​​​​Dolen yn agor mewn ffenestr newydd, or see information under ‘HMO Licensing’ below.

Houses in Multiple Occupation (HMO) are those dwellings that are occupied by a number of unrelated people. In planning terms, there are two types of HMO;

  • C4 Use Class HMOs include properties with 3-6 unrelated people
  • Sui Generis Use Class HMOs is for properties with 7 or more unrelated people.

Prior to February 2016, Planning permission was only required for Sui Generis HMOs. However, since this date planning permission is required for all HMOs whether housing 3-6 or 7+ unrelated people.

The council has produced Supplementary Planning Gu​idance (1.47mb PDF)​​​​​​​​​​Link opens in a new window on how it will assess any applications for new HMOs.

For the purposes of Class C4 and Sui Generis HMOs, an HMO has the same meaning as in section 254 of the Housing Act 2004 and does not include a converted block of flats to which section 257 of the Housing Act 2004 applies.

To fall within the HMO definition a property must be occupied as the main residence. Students, migrants and asylum seekers who do not occupy the property all year will be considered as occupying the property as their main residence and should be included in any calculation of occupant numbers. Guests visiting for a short period should not be included in any calculation of the number of occupants. ​

View section 254 of The Hous​ing Act 2004​​​​​​​​​​​External link opens in a new window.

In 2016, three planning changes took place in respect of HMOs. Firstly, the Welsh Government created a new Use Class called ‘C4’ (which is a building type classification) for smaller HMOs. Secondly, the council adopted a new Local Development Plan (LDP) which introduces a new planning policy (policy H5) controlling the sub-division or conversion of residential properties. Finally, the council produced an SPG to provide extra guidance on policy H5.

Use Class Changes
On 25th February 2016, the Welsh Government created a new use class (C4) for smaller HMOs, which previously were classed as Dwelling Houses (C3). Large HMOs for more than 7 people have been, and continue to be classed as Sui Generis. The outcome of this is that new HMOs of less than 7 persons now need planning permission, whereas previously they did not.

Local Development Plan
The Cardiff Council LDP (adopted January 2016) includes a policy which indicates that HMOs will be considered amongst other things on ‘the cumulative impact of such conversions [not] adversely affect[ing] the amenity and/or character of the area’. This means that when the council receive a planning application for a smaller (C4) or larger (Sui Generis) HMO, then the density of existing HMOs in the local area will be considered alongside other issues. The core reason for this is to try and retain some balance within communities, and to not allow entire streets to operate as HMOs.

Supplementary Planning Guidance
To complement this policy, the Council has produced Supplementary Planning Guidance (SPG) on relevant planning HMOs. This expands upon the above policy, and provides guidance on the issues that will be taken into account with regards to planning applications for HMOs. This document was approved by the council on 20 October 2016 and is accessible in the tab below.

When considering a planning application for a new HMO, the council will consider a variety of factors (see Supplementary Planning Guidance). Amongst these considerations will be the number of existing HMOs that surround a proposed new one. The council will apply a radius of 50m around the property, and within that radius, the number of existing HMOs will be assessed. That concentration of HMOs will be deemed too high if it is above 20% of dwellings in Cathays and Plasnewydd, or 10% elsewhere in the city.

Applicants can apply for pre-application advice to understand how many HMOs surround a new one (See ‘How to Apply’ section below) alternatively, an understanding of the location of HMOs can be viewed online​​​​​​​​​​​External link opens in a new window. The data may not be definitive and is for guidance only.

Planning permission must still be sought, even where you believe there to be few HMOs surrounding a proposed new one.

We have published information on how ​to apply for planning permission.

For advice please contact us via emailing or by phone on 02922 330 800.

If you would like any help or advice please contact us​​​​​​​​​​​External link opens in a new window.

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