HMO Conversion Drawings for Landlords in London

C4 small HMO or sui generis large HMO — which applies to your property?

The distinction matters because it decides which rules apply. A small HMO housing three to six unrelated sharers who share amenities is Class C4. A large HMO of seven or more occupants is sui generis and always needs planning permission, since sui generis uses sit outside the permitted development system entirely. The line also shifts with occupancy — a property let to six sharers today can tip into sui generis territory the moment a seventh tenancy is signed, which changes the planning position even though nothing about the building itself has changed. We assess your proposed occupancy and layout against both definitions before drawing, so the application matches how the property will actually be let.

Do I need planning permission for an HMO conversion in London?

Converting a family home (C3) into a small HMO (C4) is technically permitted development under national rules, but a large number of London boroughs have made an Article 4 direction that removes this right across all or part of the borough — meaning a full planning application is required even for a small, compliant HMO. Article 4 directions vary street by street in some boroughs, so two similar houses a few doors apart can sit on opposite sides of the line. Any large HMO (sui generis) needs planning permission everywhere, regardless of Article 4. We check your specific address against the relevant borough's Article 4 direction before recommending a route, since guessing wrong wastes both time and application fees.

Mandatory and additional HMO licensing — what's required?

Most HMOs need a licence from the council, separate from any planning permission. A licence application typically has to demonstrate that the property meets fire safety, amenity and space standards, that gas and electrical installations are safety-certified, and that the landlord or managing agent is a fit and proper person to hold it.

Minimum room sizes and amenity standards for HMOs

Licensing standards set minimum sizes for HMO bedrooms — commonly around 6.51m² for one adult, larger for two adults sharing, with reductions where a room contains a kitchen area — alongside requirements for adequate kitchen, bathroom and communal amenity space relative to the number of occupants. Getting a layout wrong is one of the most common reasons an HMO conversion stalls: a scheme drawn to maximise bedroom count without checking these thresholds can pass through planning and then fail licensing, forcing a costly redesign after the work is done. We design room layouts to meet these thresholds from the first floor plan, so the scheme that gets planning permission is also the scheme that will pass licensing inspection.

Fire safety, compartmentation and means of escape

An HMO has different fire safety expectations from a single dwellinghouse, because more unrelated households share the same means of escape. We coordinate this detail with the building regulations package so the drawings that go to planning, licensing and Building Control are consistent with one another, rather than three separate versions of the same building.

• A protected escape route or stairway, separated from habitable rooms by fire-resisting construction
• Fire doors and compartmentation between individual lettings and shared circulation space
• Interlinked smoke and heat alarms across all storeys and lettings
• Emergency lighting and fire safety signage where the layout and occupancy require it