HMO Conversions Westminster

HMO conversion in Westminster is shaped more by licensing than by the stock. The whole City sits under a renewed Additional HMO Licensing Scheme that took effect on 31 August 2026. Under it, a shared house or flat where three or more people from two or more households share a kitchen or bathroom needs a licence. With 91% of homes being flats, the building can be a flat share or an older converted building as well as a whole house.

In Westminster, 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 London ranges, Mayfair Studio and LetCompliance, 2026). GS Renovation Ltd, a building contractor based in Potters Bar, does the work in Westminster: 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.

Use classes and planning for a Westminster HMO

The planning question in Westminster turns on how many people will share. The London Plan glossary puts HMOs for three to six people in Use Class C4 and larger ones in sui generis, which always needs planning permission. Class L of the General Permitted Development Order makes a change from a single C3 home to a C4 HMO permitted development. It does not allow one former house to be used as two or more separate C4 HMOs.

Class L can be removed locally, and the London Plan asks boroughs weighing such directions between C3 and C4 to consider the strategic as well as local importance of HMOs. The owner or their planning agent should confirm the position for the address before the layout is drawn. The London Plan also says HMOs of a reasonable standard should generally be protected, which matters when an existing Westminster HMO is upgraded rather than returned to a family home.

Housing in Westminster

Take the 132,230 or so homes the valuation list gives Westminster: 91% flats, 9% houses, 48% from before 1919, 10% interwar and 40% post-war.

Mandatory and additional HMO licensing across Westminster

A licence is needed before a Westminster HMO is let, and the landlord applies for it. GOV.UK defines a large HMO as one rented to 5 or more people who form more than 1 household, which needs a mandatory licence. Westminster first brought in borough-wide additional licensing on 30 August 2021. The renewed scheme was designated on 21 April 2026, took effect on 31 August 2026 and runs until 30 August 2031.

Mandatory licensing does not reach a flat in a purpose-built block of three or more self-contained flats; where such a flat is shared, it is the council's additional scheme, if any, that applies.

Additional licensing reaches flat shares, bedsits and some converted flats that fall outside the mandatory scheme. Westminster also says a building converted into flats that are not all fully self contained may need a mandatory or additional licence even with no shared facilities. That catches older conversions, so a survey of the separation between units comes before any quote. GOV.UK warns that renting out an unlicensed HMO can lead to an unlimited fine, so the build finishes before the first tenancy.

Room sizes, kitchens and sharing under Westminster HMO standards

Westminster's HMO standards turn into dimensions on the drawing. The council has produced four sets of standards for different types of shared property, updated in April 2021, and may attach works conditions to a licence to achieve them. For a shared house or flat, a kitchen must be at least 5.5 square metres and arranged for safe access and use. No more than two people may sleep in one bedroom, and a child counts as a person.

Bedrooms must also meet the national minimum sizes that apply as licence conditions: 6.51 square metres for one person over 10, 10.22 for two, and no sleeping room under 4.64 square metres. Where statutory bedroom sizes are breached, Westminster says it has a legal duty to act but allows an 18-month period to put it right. The sizes are measured on usable floor area: floor under 1.5 metres of ceiling height and fixed boxing do not count, though a door swing does. The 18 months is a correction period, not a design allowance, so we set out partitions to the sizes on the approved plan and check them before plastering. Bathrooms and WCs are sized to the occupancy the licence will name.

Fire safety, sound and energy in a Westminster HMO

Fire safety is the core of an HMO build in Westminster. Bedroom doors become fire doors with self closers, the escape stair is protected, and linked fire detection and alarms go in to the grade set for the building, following Part B and the LACORS housing fire safety guidance. For buildings of self-contained flats that count as HMOs, Westminster's standard treats 60 minutes as the benchmark but accepts 30 minutes with appropriate automatic fire detection in most existing conversions.

Sound between lettings matters more than in a family house, because each room is a separate household with its own hours. Stud partitions are filled with mineral wool and floors between bedrooms get a resilient layer. Energy rules apply too: since 1 April 2020 a landlord cannot let, or continue to let, a home with an EPC rating below E unless a valid exemption is registered. The government has set 1 October 2030 for private lets to reach EPC C, subject to regulations, so insulation and heating controls belong in the scope while floors and walls are open.

• Electrics extended to every bedroom, certified by a registered electrician
• Hot water sized for several sharers showering at once, with any gas work by a Gas Safe registered engineer
• Emergency lighting on the escape route where the house needs it

VOA Council Tax stock of properties, March 2025, for all 24 statistical areas in Westminster. Counts rounded by the VOA.

Useful next reading for a hmo conversions project in Westminster: bathroom renovation in Westminster, our Westminster area guide, what a main building contractor does, kitchen fitting in London, how we handle hmo conversions across London and Getting Planning Permission.

Why Choose GS Renovation in Westminster

An HMO has to pass a licence inspection as well as building control, so we build to both from the first drawing. We set out rooms to the approved sizes and check them before plastering, install fire doors, detection and protected escape routes in the order inspectors want to see them, and coordinate the registered electrician and a registered gas engineer. The landlord applies for the licence; we hand over the certificates and a record of the fire safety work to support it.

• Building control applications and inspections coordinated for you
• Sound lining between bedrooms so one sharer does not keep another awake
• Detection laid out to the grade the council's HMO fire guidance sets

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