HMO Conversions London

HMO conversions in London turn a family house into a shared house let room by room to unrelated tenants, or bring an existing house in multiple occupation up to the standard its licence demands. This guide is written for a London landlord or investor who needs to know what the council will allow, what the licence conditions mean in bricks and plasterboard, what the build costs and how it runs. You, or your agent, apply for planning permission and the HMO licence. Your designer draws the room layout, any new opening or steel is designed by the structural engineer we appoint, and building control inspects the notifiable work. We build the fire doors, detection, partitions, kitchens and bathrooms to the drawings and the licence standard. An HMO stays one building shared by several households, so the work centres on fire safety and shared facilities.

Across London, a light HMO conversion for four to six tenants typically costs £40,000 to £75,000 in construction, or £90,000 to £150,000 with an en-suite to every bedroom (indicative ranges, Mayfair Studio and LetCompliance, 2026). GS Renovation Ltd, a building contractor based in Potters Bar, does the work in London: we build the fire doors, detection, bathrooms and kitchens to the council's HMO standards, the landlord applies for the licence, and a registered electrician certifies the electrics.

Which London houses make a workable HMO?

A London house makes a workable HMO when it has enough bedrooms of a usable size, a stair that can serve as a safe way out, and room for kitchens and bathrooms in proportion to the tenants. Three-storey Victorian and Edwardian terraces often qualify, as do larger interwar semis. Both reception rooms can become lettable rooms only where the council's amenity standard allows it, which usually means a larger shared kitchen-diner or keeping one communal room. Each bedroom must meet the minimum floor area after fitted cupboards and boxing, and any area where the ceiling is lower than 1.5 metres is excluded, which is where loft and eaves rooms most often fail. Every extra bedroom adds a sharer the kitchen and bathrooms must serve, so plan the two together.

Safe escape sets the room count before rent does. In a shared house each tenant must be able to leave their room along a protected route to the front door, so the stair and hall become the escape route. A kitchen that opens onto that route, or a bedroom reached only through another room, usually has to change. Loft and basement rooms raise the hardest questions, because escape from them is longer or below ground. Plan the room count from the escape route and shared facilities outwards, then see how many lettable rooms remain. A house that gives five good rooms is a better HMO than one squeezed to seven, which would also make it a large HMO needing planning permission.

How an HMO conversion runs on site in London

On site, an HMO conversion in London is organised around the fire strategy and the licence conditions. We survey the house against your designer's layout and flag any room below the size standard or any door that cannot be made a fire door. Letting rooms is a business, so CDM 2015 treats you as a commercial client rather than a domestic one. Where more than one contractor works on site, you appoint the principal designer and principal contractor in writing. After strip-out we build the partitions and any openings the engineer has designed, then run the extra bathroom pipework and the alarm wiring. Once building control has inspected, we plaster, hang the fire doors with closers and seals, and fit the kitchens and bathrooms.

Licensing upgrades are often built with tenants still living in the house. Your duties as manager continue while we work, so the escape route is never left blocked and the alarm system is live at the end of every day, even when a door is off for replacement. Tenants keep their right to quiet enjoyment, so you give each one written notice before we need their room, usually at least 24 hours. We work room by room and phase kitchens and bathrooms so one of each is always in use. Noisy stages stay within the council's permitted hours, and you tell tenants which days they fall on. Where the licence sets a date to finish works, or the council has served an improvement notice under the Housing Act 2004, that date sets the programme, so tell us when we survey.

Planning permission and building regulations for an HMO in London

In much of outer London you will need planning permission even for a three-person HMO, because the council has removed the permitted development right with an Article 4 direction. Barnet, Bexley, Enfield, Greenwich, Redbridge and Sutton, among others, have directions covering the whole borough, and Brent, Croydon and Newham have them too. Where no direction applies, changing a family house in class C3 to a small HMO for three to six unrelated people in class C4 is permitted development. A shared house for seven or more people is sui generis, outside any use class, and turning a family house into one needs planning permission. Check the council's Article 4 map for the exact address, and the borough page for your area, before you buy.

Building control normally treats a change to a small HMO as building work, not a material change of use. Bedsit layouts and larger HMOs can count as rooms for residential purposes, so confirm this before the layout is fixed. If they count, Part E sound insulation applies between letting rooms. Structural openings, new partitions on the escape route, new bathrooms and hot water, drainage and new circuits must comply with Parts A, B, F, G, H, L and P as they apply. A G3-qualified installer fits any unvented cylinder. Because the Regulatory Reform (Fire Safety) Order 2005 applies to the common parts, building control needs a full plans application, not a building notice. Once let, the Management of Houses in Multiple Occupation (England) Regulations 2006 require the manager to keep the escape route clear, the alarms maintained and the common parts in good order.

HMO licensing, room sizes and fire safety standards in London

An HMO in London needs a mandatory licence when five or more people forming two or more households share it. A flat HMO in a purpose-built block of three or more flats falls outside mandatory licensing, but an additional licensing scheme can cover it, as it can smaller HMOs. The landlord applies to the council, and the licence comes with conditions an officer will inspect. Since 2018 the national minimum room sizes have been mandatory conditions in England: 6.51 square metres for one adult, 10.22 square metres for two, and no room under 4.64 square metres used for sleeping. Schedule 3 to the 2006 HMO licensing regulations sets minimum bathrooms, WCs and kitchens by the number of sharers, and councils publish their own amenity standards on top.

Fire safety carries more of the licence building work than anything else, and the standard is risk-based. The recognised guide is the LACORS housing fire safety guidance, read with Part B and the council's own HMO fire standard. In most shared houses of three or more storeys that means a protected escape route from every room, 30-minute fire doors with smoke seals and self-closers to bedrooms and the kitchen, and a mains-wired, interlinked alarm system. A low-risk two-storey house may need less, and the fire risk assessment sets the level. Sound insulation between rooms is worth planning at the same stage. Where the let needs an EPC, the minimum E rating has applied to new and existing lets since April 2020, subject to valid exemptions.

What does an HMO conversion cost in London?

A light HMO conversion of a London house for four to six tenants, with shared kitchen and bathrooms and little structural work, typically costs £40,000 to £75,000 in construction alone. A full conversion of a five or six bedroom house with an en-suite to each room runs £90,000 to £150,000, again build only. Both are indicative London ranges from Mayfair Studio, 2026, and planning, design and licence fees sit on top. Mayfair notes fire safety work is often inside its bands but sometimes billed separately, and LetCompliance, 2026, prices that package in a typical five-bed HMO at £5,000 to £9,500. Its typical total for a three-bed semi converted to a five-person HMO in London and the South East, £35,000 to £60,000, includes the licence fee and furniture, so it is not a build-only figure.

The number of bathrooms moves an HMO price more than anything else, because the council's amenity ratio ties it to the number of tenants. Adding an en-suite costs £3,500 to £8,000 per room (Mayfair Studio, 2026), and a second shared bathroom £4,000 to £9,000 (LetCompliance, 2026), depending on layout, plumbing, extractor and tiling. Five en-suites add far more than one extra shared bathroom, though they can lift the rent. Work the numbers per room: a sixth letting room that takes the house past the council's ratio brings another bathroom or WC with it, and sometimes a second kitchen. Period houses add cost where panelled doors cannot reach a 30-minute rating, or lath and plaster ceilings under the escape route need fire-resisting boards.

Why London HMOs fail licence inspections, and how to pick a builder for one

HMOs commonly fail licence inspections on fire safety or room size. Typical faults are standard doors with a closer screwed on and called fire doors, frames with no intumescent seal, and battery smoke alarms where a mains-wired, interlinked system was required. Pipes and cables through ceilings are often left unsealed, which breaks the compartment the fire doors rely on. A room can fall below the minimum once fitted cupboards or boxing go in, or because part of it sits under a ceiling lower than 1.5 metres. A kitchen with too few sinks or cooking rings for the tenants is another. The council can then license fewer occupants than you applied for, or set conditions with a deadline, and the fix then means opening finished walls.

Judge an HMO quotation by how it answers the licence conditions, since those decide whether the rooms can be let at all. Ask how the fire doors will be supplied and hung, whether they come as certified door sets, and who will fire-stop the service penetrations. Ask how the alarm system will be specified and who certifies the electrics. A careful builder measures every bedroom against the national minimum sizes before quoting and tells you if a room will not pass. Check that the quote names the council's amenity standard and the occupancy it is built for, so the kitchen and bathroom count can be checked against it. If your house sits under an Article 4 direction, do not let anyone start before permission is granted.

• Sound lining to bedroom walls and party walls
• Hot water sized for several sharers showering at once, with any gas work by a Gas Safe registered engineer
• Protected escape routes through the hall, stair and landings

Alongside hmo conversions in London, the pages that usually help next are bathroom renovation in London, bathroom fitting in London, what a snagging list covers and Kitchen Renovation Cost.

Working With GS Renovation in London

An HMO has to pass a licence inspection as well as building control, and GS Renovation Ltd (company number 14611254) builds with both in mind. Our founder, Abdelaaziz Saaid, runs the work and has over 30 years of hands-on experience. One named contact handles your job from the first survey to handover, and our own trades build the partitions, fire work, kitchens and bathrooms rather than a subcontractor chain. We coordinate building control on every notifiable job. After the survey you receive an itemised written quotation, and MyBuilder reviewers rate us 4.9 from 31 reviews.

• Free, no-obligation quotations
• Kitchens and bathrooms counted against the council's amenity standard
• Every bedroom measured against the national minimum room sizes

Checked by Abdelaaziz Saaid, founder and director of GS Renovation Ltd (Companies House no. 14611254).