Licensed · Fire-compliant · Principal contractor
HMO Conversions in London
Licensed HMO fit-out from 3 to 8 rooms. Fire compartmentation, FD30 and FD60 fire doors, emergency lighting, room layouts to licensing standard, and Building Control sign-off. Fixed price before we start.
Why HMO conversions need the right contractor
An HMO conversion is one of the most regulated categories of residential construction. The fire safety standards, room size requirements, facilities standards, and Building Control obligations are all mandatory — not optional upgrades.
The consequences of getting it wrong are serious: Building Control can issue prohibition notices preventing the property from being occupied, local authorities can refuse or revoke HMO licences, and landlords face significant fines and potential prosecution for non-compliant HMO management.
We build HMOs that pass Building Control inspection and support licence approval. That means understanding the licensing conditions before work starts, designing the layout to meet room size minimums, specifying fire doors and compartmentation to the correct standard, and providing the completion documentation the local authority needs.
What an HMO conversion includes
We manage the full sequence under one contract. Every element below is coordinated by our site team.
Fire compartmentation
- ✓FD30 and FD60 fire doors throughout — to Building Control specification
- ✓Intumescent strips and cold smoke seals to all fire doors
- ✓Fire-resistant partition walls between rooms and common areas
- ✓Ceiling upgrades to achieve 30-minute fire resistance where required
- ✓Fire stopping to all service penetrations
Emergency lighting & detection
- ✓Emergency escape lighting throughout — all circulation routes and stairwells
- ✓Interlinked mains-wired smoke detectors in all rooms and common areas
- ✓Heat detectors in kitchens
- ✓Fire alarm panel where required under HMO licence conditions
- ✓Emergency lighting to WCs, bathrooms and shared spaces
Structural & layout works
- ✓Room subdivision — new stud partitions to create additional lettable rooms
- ✓Loft conversion to create additional rooms where applicable
- ✓Load-bearing wall removal and RSJ installation
- ✓New ensuite bathrooms — plumbing, tiling, ventilation, sanitary ware
- ✓Corridor and communal area reconfiguration
Kitchen & bathroom fit-out
- ✓HMO-specification kitchen — sized and specified for occupant numbers
- ✓Additional kitchen units, sockets and extraction where required
- ✓Shared bathroom refurbishment — waterproof tiling, new suite, ventilation
- ✓Ensuite bathrooms in bedrooms where licenced and specified
- ✓Cold water storage and hot water systems to meet demand
M&E and services
- ✓Full electrical survey and upgrade to 18th Edition IET Wiring Regulations
- ✓Separate metering or sub-metering where required
- ✓Plumbing upgrades to meet hot water demand for occupant numbers
- ✓Ventilation upgrades — bathrooms, WCs, kitchen extraction
- ✓TV aerial distribution and data points where specified
Decoration and completion
- ✓Full replaster and skim where required
- ✓Mist coat and two coats of emulsion throughout
- ✓Skirting boards, architraves, and door sets
- ✓Floor preparation (screed or boarding) — floor finishes are client-supplied
- ✓Deep clean on completion
All second-fix materials (floor finishes, sanitaryware, kitchen units) are client-supplied unless specifically agreed otherwise. RCB does not install carpet.
HMO conversion costs in London (2026)
These are guide ranges only. Final cost depends on the number of rooms, structural complexity, extent of fire compartmentation works, ensuite provision, and the current condition of the property.
3–4 room HMO — light conversion
Fire doors, emergency lighting, smoke detection, kitchen upgrade. Minimal structural work. Shared bathroom(s) only.
5–6 room HMO — standard conversion
Fire compartmentation, FD30 doors, emergency lighting, new or upgraded kitchen, shared bathrooms. May include one structural alteration.
7–8 room HMO — full conversion
Full fire compartmentation, all FD30/FD60 doors, new kitchen to HMO spec, ensuite bathrooms, structural alterations, full M&E upgrade.
HMO conversion with loft
Adds a loft conversion to create additional lettable rooms. Dormer or hip-to-gable, structural floor upgrade, fire compartmentation extended to loft level.
A site visit is required before a reliable estimate can be provided. These figures are for budgeting only.
How we deliver HMO conversions
Feasibility and licence check
We assess your property, review the local authority HMO licence requirements, and advise on room sizes, facilities standards, and fire safety obligations before any work starts.
Layout and scope agreement
We agree the room layout, number of lettable rooms, ensuite provision, and kitchen and bathroom specification. A full written scope of works is issued before you commit to anything.
Fixed price issued
You receive an itemised fixed price for the full works. No vague estimates — a scope-referenced figure agreed before work starts.
Building Control notification
We notify Building Control and manage all inspections throughout. Fire compartmentation, emergency lighting, and structural works are all inspected and signed off.
Managed delivery
We manage all trades on site — structural, electrical, plumbing, fire doors, plastering, decoration. One point of contact, one programme, one team.
Completion and licence support
We complete to Building Control and HMO licence standard. We can prepare the documentation pack for your local authority licence application if required.
Why choose RCB Design & Build for HMO conversions?
Compliance-first approach
We understand what Building Control and local authority licensing officers require. We design to those requirements, not around them.
Fire door and compartmentation specialists
We specify and install fire doors, cold smoke seals, intumescent strips, and fire-resistant partitions correctly. Not all contractors do.
Fixed price before work starts
Your price is agreed and documented before a tool goes on site. You know the cost of the conversion before you commit.
Building Control managed
We notify Building Control and manage all inspections. You receive a completion certificate you can rely on for licensing applications.
Principal contractor
One team manages every trade from structural to decoration. No trade coordination for you to manage. One point of contact throughout.
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Common questions about HMO conversions
How much does an HMO conversion cost in London?
A licensed HMO conversion in London typically costs £40,000–£90,000 depending on the number of rooms, extent of structural work, ensuite provision, and the current condition of the property. A 5-room HMO with no structural changes and one shared bathroom sits at the lower end. An 8-room HMO with ensuite rooms, full structural work, and a new kitchen sits at the upper end. A site visit is required before a reliable figure can be given.
Do I need planning permission for an HMO conversion?
Converting a property to a small HMO (3–6 people, Use Class C4) may not require planning permission if the property is already a dwelling. However, some London boroughs have Article 4 Directions that remove permitted development rights for C4 HMO conversions — Newham, Tower Hamlets, Hackney, and others. We check the applicable rules before work starts. Large HMOs (7+ occupants, Sui Generis) always require full planning permission.
What is fire compartmentation and why does it matter?
Fire compartmentation means constructing walls, floors, ceilings, and door assemblies that resist the spread of fire for a defined period — typically 30 or 60 minutes. For licensed HMOs, Building Control requires that each room forms a fire compartment, that all doors to corridors are FD30 fire doors with cold smoke seals, and that ceiling and wall construction meets 30-minute fire resistance standards. This is not optional — failure to comply is a criminal offence under HMO licensing legislation.
What are the minimum room sizes for an HMO?
Under the Housing Act 2004 national minimum room size standards: a room used for sleeping by one adult must be no smaller than 6.51m². A room used for sleeping by two adults must be no smaller than 10.22m². Rooms below 4.64m² cannot be used as sleeping accommodation at all. Some local authorities set higher minimums — always check with the relevant London borough before finalising your layout.
Will you manage the HMO licence application?
We build the property to the standard required for licensing and can prepare the construction documentation and completion certificate pack. The actual licence application is submitted by the property owner or their agent to the local authority. We can advise on what documentation is needed and help you prepare the supporting evidence.
How long does an HMO conversion take?
A 5–6 room HMO conversion with moderate structural work typically takes 10–16 weeks on site. A larger 7–8 room project with full structural works, ensuite bathrooms, and kitchen replacement typically takes 16–24 weeks. We issue a programme before work starts so you can plan void periods and mortgage obligations accordingly.
Plan your London HMO conversion
Free site survey. Compliance check included. Fixed price before we start. Building Control managed throughout.
Or call us on 07359 872594