There are two central tests
The definition concerns a building, or part of a building, converted into self-contained flats. The relevant construction standard and the proportion of owner-occupied flats must both be assessed. A modern, compliant block is not a Section 257 HMO merely because most flats are rented; nor is every old conversion automatically within the definition. [1]
For conversions before 1 June 1992, the relevant benchmark is the 1991 Building Regulations. For later conversions, the assessment concerns the applicable requirements when the conversion was undertaken and whether the relevant deficiencies remain. [1]
The ownership test is less than two-thirds owner-occupied, not simply whether the freeholder lets out any accommodation. Establish which flats qualify as owner-occupied under the legal definition. Other statutory exclusions and occupation requirements also need checking. [1] [2]
What evidence should be gathered?
Ask for the conversion date, building-control records, approved drawings and evidence of subsequent remedial work. Compare these with the actual layout and construction, and prepare a schedule showing the tenure and occupation of each flat. [1] [2]
Missing paperwork should prompt investigation rather than an automatic conclusion that the physical conversion failed the relevant standard. Equally, an old drawing is not proof that the work was built as drawn. The purpose of the evidence exercise is to establish the building's actual position.
Does the block need an HMO licence?
Section 257 blocks are not automatically covered by national mandatory HMO licensing. A council can include relevant converted blocks in an additional licensing scheme, so the scheme's wording and exclusions must be checked for the address. [3]
An individual flat within a block may also meet an HMO definition because of how its occupants share it. Do not combine every resident in separate self-contained flats into a single five-person shared-HMO calculation. [3]
The rules of an additional scheme in another city should not be imported into London or Epping Forest. Use national definition guidance to understand Section 257, then inspect the local designation to establish licensing. [3]
Management and fire safety still matter
Salford's guidance explains that Section 257 HMOs are subject to the applicable 2007 management regulations and identifies fire-risk assessment duties for relevant common parts. An alarm service certificate does not replace a suitable fire-risk assessment. [2]
Address the actual deficiencies and risks rather than treating the classification as only a licence-form question. Where construction work is proposed, agree the relevant building-regulations route and the evidence needed to demonstrate the completed work. [4]
Review changes in occupation and construction
A change in the balance of owner-occupation and letting, or work correcting the conversion, may affect the assessment. Keep the tenure schedule and technical records current instead of assuming that an earlier classification remains conclusive indefinitely. [1] [2]
For a purchase, licensing dispute or enforcement case, obtain a property-specific assessment of the construction and statutory definition before relying on an exemption.