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What is Section 257 HMO?
Last verified 31 October 2026
A section 257 HMO is a converted block of flats treated as a house in multiple occupation under section 257 of the Housing Act 2004. It applies where the conversion did not meet the appropriate building standards and fewer than two thirds of the self-contained flats are owner-occupied.
Why it matters to landlords
The test is about the building, not about a single flat. For blocks completed before 1 June 1992, the standard is the equivalent of the 1991 Building Regulations as they stood on 1 June 1992. For other blocks, it is the requirements under building regulations at the time of conversion. A flat counts as owner-occupied if it is occupied by a leaseholder whose lease was granted for more than 21 years, by the freeholder, or by a member of either household.
The section does not change the HMO status of any individual flat in the block. In practice this matters to freeholders, management companies and landlords of one flat in an older converted building, because the block itself is treated as an HMO and may need a licence. Ask the council whether it treats the building as a section 257 HMO before you buy, and ask the freeholder who holds any licence.
Example
Neil is buying a leasehold flat in a house converted in 1988 into six flats. Only one flat is lived in by its leaseholder, which is under two thirds. The council confirms the conversion did not meet the 1991 standard, so the building is a section 257 HMO and he asks the freeholder about the licence before exchange.
Related terms
- HMO (House in Multiple Occupation)
- Mandatory HMO licensing
- Building regulations
- HMO licence
- HMO management regulations