The Southsea HMO appeal at Montgomerie Road has succeeded, allowing a five-person house in multiple occupation (HMO) to become an eight-person, eight-bedroom property. Inspector R Cahalane allowed the appeal on 9 November 2026, but refused the applicant’s separate claim for costs against Portsmouth City Council.
The appeal concerned an existing Class C4 HMO in a densely populated residential area of Southsea. It followed the council’s failure to determine the application within the prescribed period and a subsequent Planning Committee resolution that it would have refused permission. The council’s officers had previously recommended approval.
The Southsea HMO appeal is particularly revealing because 29 of the 76 properties within 50 metres were already HMOs, a concentration of 38.2%. The Inspector nevertheless gave substantial weight to the lawful existing five-person use and found that the additional three occupiers would not materially change the number of HMO properties in the locality.
Why the Southsea HMO appeal succeeded
Portsmouth’s adopted Core Strategy Policy PCS20 seeks mixed and balanced communities, while its 2019 HMO Supplementary Planning Document uses a 10% concentration threshold within 50 metres. At first sight, a property surrounded by HMOs at nearly four times that threshold might seem unlikely to secure permission for further intensification.
But the Southsea HMO appeal did not involve converting an ordinary family dwelling into an HMO for the first time. The property was already an HMO licensed for five people. The Inspector treated that established lawful use as the starting point, rather than assessing the proposal as though it created another HMO address. That distinction determined the weight attached to the council’s concentration objection.
The Inspector described the existing five-person occupancy as an “important material consideration” and a lawful fallback. Increasing the number of residents to eight would not increase the local count of HMO properties. On the evidence available, it would not materially change the existing mix and balance of households or conflict with the adopted community-balance policy.
The Inspector also examined the actual surroundings rather than inferring harm from a percentage alone. During the site visit, the neighbouring HMO buildings did not appear neglected. The Inspector found no convincing qualitative evidence that litter, noise or other local character harm could be attributed to HMOs in the immediate area. That was a site-specific finding, not a ruling that HMO concentration policies are irrelevant.
The emerging Portsmouth Local Plan took a stricter approach. Policy PLP20.2 would normally restrict intensification where HMO concentrations exceed 10%, subject to exceptional circumstances. However, the plan was still undergoing examination, and the Inspector could not be confident that the policy would be adopted unchanged. The Inspector therefore gave it insufficient weight to override the adopted development plan in this Southsea HMO appeal.
Room sizes, outdoor space and protected coastal habitats
The council’s committee had raised concerns about the garden being too small for eight occupiers. The Inspector acknowledged that the rear space would be relatively modest after a proposed extension, but found it could still accommodate seating and clothes drying. In the context of a densely developed urban street, the provision was acceptable.
The Inspector also found that all bedrooms would comfortably exceed the room-size standards in Portsmouth’s HMO guidance, including after allowing for sloping ceilings at second-floor level. Natural light and ceiling heights were satisfactory. The rear extension and loft conversion shown on the plans were treated separately, because the appeal was not a formal determination of whether those building works were permitted development.
There remained an important environmental issue. Adding three residents could increase recreational pressure on the Solent’s protected coastal habitats and contribute nutrients through wastewater. In the Southsea HMO appeal, the appellant submitted a signed section 111 undertaking providing £1,044 for recreational mitigation and £2,750 for nutrient mitigation.
Following an appropriate assessment under the Habitats Regulations, and consultation with Natural England, the Inspector was satisfied that the secured measures avoided adverse effects on the integrity of the relevant European sites. Conditions also require evidence of water efficiency, and the eight-person use cannot begin until specified alterations, cycle storage and refuse facilities are provided.
The application is a reminder that HMO planning applications should distinguish the existing lawful occupancy from any additional intensity, address the quality of accommodation and identify mitigation requirements. A numerical threshold may be important, but it is not a substitute for analysing what would actually change.
Why the costs claim failed
The applicant sought a full costs award, arguing that Portsmouth had acted unreasonably. The separate decision on the same date reached the opposite outcome from the planning appeal: the Inspector refused to make any award. Permission to develop and entitlement to costs involve different questions.
In the costs decision, Inspector Cahalane wrote: “A Planning Committee is entitled to take a decision contrary to the advice of its professional officers.” The Inspector added that the reasons must nevertheless be supported by substantive evidence. The committee had raised issues of HMO concentration, local character and amenity which, although not decisive on planning merits, were sufficiently specific to make defending the appeal reasonable.
The Inspector did criticise the authority’s handling of the application. Emails showed that the applicant had received repeated assurances, over almost four months, that it would go before the next available committee meeting. Those assurances were not honoured and the application remained undetermined well beyond the prescribed period.
However, the costs decision explained that delay and frustration do not, by themselves, establish the unnecessary or wasted appeal expense required for an award. The mitigation undertaking submitted during the appeal did not change that conclusion. The Southsea HMO appeal therefore provides a useful contrast with other cases where unsupported refusal reasons have led to costs awards.
For comparison, a different Portsmouth HMO appeal decided in October resulted in a partial costs award. The outcomes are not inconsistent: the evidence supporting the authority’s conduct has to be examined in each case, independently of whether the proposal is ultimately allowed.
What the decision means for other HMO proposals
For owners considering an increase from Class C4 to a larger sui generis HMO, the key lesson is to establish precisely what use is already lawful. Evidence of the existing planning position, occupancy, room arrangements and conditions can materially affect the assessment. Planning permission remains necessary for the proposed change to an eight-person HMO.
Councils, meanwhile, should distinguish whether an intensification produces another HMO property, changes its occupancy, or generates identifiable effects on neighbours and local services. Emerging plan restrictions matter, but their weight depends on the stage of preparation and the likelihood of adoption in their current form. See Planning Geek’s guide to HMO planning policies for the wider policy context.
The Southsea HMO appeal also shows why a successful appeal is not automatically a successful costs application. Applicants still need evidence of unreasonable behaviour causing unnecessary expense, rather than simply evidence that a committee was slow or its planning judgement was rejected.
Appeal reference 6014163 was decided by Inspector R Cahalane on 9 November 2026. The separate costs decision concerns the same reference and date. The appeal decision is also available on AppealBase.
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