Section 257 HMOs Explained: Licensing for Converted Flats

Not every HMO licensing trap looks like an HMO. A significant number of London landlords own a single self-contained flat in a converted building with no idea that Section 257 of the Housing Act 2004 could mean the entire building requires an HMO licence — not because of how any individual flat is let, but because of how the building itself was converted.

What is a Section 257 HMO?

Section 257 applies to buildings that have been converted into self-contained flats where the conversion did not meet the standards of the Building Regulations 1991 (typically because the conversion happened before June 1992), and where less than two-thirds of the flats are owner-occupied. If both conditions apply, the building as a whole can be treated as an HMO for licensing purposes — regardless of whether any single flat would ordinarily be considered a shared house.

Why this catches landlords out

Most landlords think about HMO licensing in terms of their own tenancy arrangement — how many unrelated people share their specific flat. Section 257 doesn't work that way. A landlord who owns and lets a single, perfectly ordinary self-contained one-bedroom flat can still be caught if the wider building meets the two conditions above, because the licensing obligation attaches to the building's structure and ownership pattern, not to the individual let.

What's assessed

A Section 257 licence application looks at the building's common parts — fire doors, means of escape, fire detection in shared hallways and stairwells, and the electrical safety of shared services. The electrical certification work required to evidence compliance (an EICR covering communal areas, for example) is a distinct piece of work from the licence application itself — our sister site, electrician247.london, handles that certification side for London landlords, while we handle the licence application and council liaison.

What to do if you think this applies to you

If you own a flat in a converted building and you're not sure whether the wider building falls under Section 257, don't guess. Contact us with the building's details — age, conversion date if known, and the ownership split between flats — and we'll confirm whether a licence is required and handle the application if it is.