Section 257 HMO Licensing in Portsmouth: Converted Buildings

Section 257 of the Housing Act 2004 catches a category of building that many freeholders and block managers do not think of as an HMO: a house or commercial building converted into self-contained flats that did not meet the Building Regulations standard applicable at the time, where two-thirds or more of the flats are rented privately. Portsmouth's Additional HMO Licensing scheme brings these blocks within scope.

What Triggers a Section 257 Licence

Three conditions must all be true:

1. Conversion standard. The conversion did not meet the Building Regulations 1991 standards or the subsequent regulations in force at the time of conversion. A pre-1991 date or a missing completion certificate alone does not establish non-compliance.
2. Ownership split. Less than one-third of the flats are owner-occupied. Put another way, two-thirds or more are rented privately.
3. Additional licensing scope. Portsmouth's Additional Licensing designation (active citywide until 31 August 2028) explicitly includes Section 257 buildings.

If all three apply, the block itself needs an additional HMO licence, typically held by the freeholder or head block manager. This is a licence for the building as a whole, not for individual flats.

Individual Flats Can Need Their Own Licence

A Section 257 licence covers the common parts and structural management of the building. If an individual flat within the block is itself let to three or more unrelated people who share amenities, that flat also needs its own additional HMO licence. The two licences are separate and additive — the freeholder or block manager holds the building licence, while the flat landlord holds the individual flat licence.

Fees and Per-Flat Surcharges

The base fee for a Section 257 additional licence follows the standard additional HMO schedule (£886 for a new 5-year licence at 2026 rates). On top of that, Portsmouth adds £74 for each flat under the licence holder's control. A converted Victorian house with four rented flats would add £296 to the Part 2 fee.

How to Check Your Building

The critical question is whether the conversion met the Building Regulations standard applicable at the time. If a completion certificate is unavailable, check with Portsmouth's Building Control team; its absence alone does not establish non-compliance. For post-1991 conversions, check whether the conversion met the regulations then in force. A missing approval record is a reason to verify compliance, but does not by itself establish that the building falls within Section 257.

Council tax records and the Land Registry title register help establish whether the ownership split meets the two-thirds rental threshold.

Our Portsmouth Landlord Licensing Guide covers Section 257 classification in detail, including how building licences interact with individual flat licences and the fee calculations for multi-unit blocks.

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