HMO Conversions · London
Turning houses into high-yield HMOs takes more than a floor plan and a building notice. It takes someone who understands the planning system, knows how to design rooms that actually let well, and can manage the build without the project dragging on for months. That is what we do.
Talk to Us About Your Project
What We Do
Most developers we work with have a similar story. They have bought a property, or they are about to, and they want to convert it into a 5, 6 or 7-bed HMO. They have spoken to a few architectural designers and builders but nobody seems to handle the whole thing - the design, the planning application, the building regs, the actual build.
We do all of it under one roof. As residential architectural designers in London, Rosace Design Studio handles architecture and construction under one contract, so you are not coordinating between three or four different companies. You brief us once and we take it from there.
We work with developers and landlords across London who are converting properties from C3 residential use into C4 or sui generis HMOs. That means we deal with Article 4 Directions regularly, and we know what planning officers in each borough are looking for.
Most of our HMO projects also involve an extension. A rear extension or loft conversion adds bedrooms and dramatically improves the yield on the property, and we handle the extension and the conversion as one coordinated project.
Types of HMO Conversion
Small HMOs (C4 use class) are properties occupied by 3 to 6 unrelated people who share facilities such as a kitchen or bathroom. In boroughs without an Article 4 Direction, converting a house to a C4 HMO is permitted development. In boroughs with an Article 4, you need full planning permission.
Large HMOs (sui generis) are properties occupied by 7 or more people. These always require planning permission regardless of Article 4 status. They also need a mandatory HMO licence from the council, which sets standards for room sizes, facilities and fire safety. Most serious HMO developers aim for this category because yields are higher.
HMO with extension is the most common project type we see. Developers buy a 3-bed terraced house and want to extend at the rear and into the loft to create 6 or 7 lettable bedrooms, each with an en-suite. We design the extension and the internal layout together, submit one planning application, and build it all under one contract.
HMO with basement conversion works particularly well on Victorian properties that have existing cellars. Converting the basement adds a bedroom or two without using garden space, and it can be combined with a rear extension above. We coordinate the structural work, tanking, lightwells and internal fit-out as part of the same project.
Planning & Article 4
Planning is where most HMO conversions succeed or fail. Getting the application right first time saves months and protects your investment. Rosace Design Studio prepares and submits HMO planning applications across London, and we know what each borough expects.
Most inner London boroughs now have Article 4 Directions in place. That means converting even a small house into a C4 HMO requires full planning permission. Boroughs including Wandsworth, Hackney, Islington, Camden, Lewisham, Southwark, Lambeth, Newham and Tower Hamlets all have Article 4 coverage. For more detail on how Article 4 works, read our guide to Article 4 and HMO planning in London.
For large HMOs with 7 or more occupants, the use class changes to sui generis, and planning permission is always required regardless of whether an Article 4 Direction applies. These applications are scrutinised more closely by councils, particularly around impact on the character of the area, parking, waste management and neighbour amenity.
We prepare full planning applications including floor plans, elevations, design and access statements, waste management plans and parking assessments. We handle all correspondence with the council and attend planning committee meetings when required.
Cost Guide
Construction costs for HMO conversions in London typically range from £1,500 to £2,500 per square metre, depending on the scope of work and the quality of finish. The lower end covers straightforward internal reconfiguration with basic en-suites. The higher end applies to projects that include structural alterations, a rear extension or significant upgrades to fire safety and sound insulation.
As a rough guide for 2026: converting a 3-bed terraced house into a 6-bed HMO with a single-storey rear extension typically costs between £80,000 and £150,000 for the construction. Adding a loft conversion pushes that towards £130,000 to £200,000. These figures include the internal fit-out, en-suites, kitchen and all finishes.
Professional fees - architectural design, planning application, structural engineering and building regulations - usually add between £8,000 and £20,000 on top, depending on the complexity of the project and whether an Article 4 application is involved.
Because Rosace Design Studio handles both architecture and construction, we provide cost estimates early in the design process. You know what the project will cost before you commit to the planning application, which means you can model the investment properly and make informed decisions about specification.
Cost Calculator
Tell us the size, location and finish level. Our calculator returns a realistic range for your extension or loft conversion, with a detailed breakdown available.
For developers
An Article 4 direction is what most often removes the permitted development route on a house to small HMO conversion. Check the designations recorded over a site postcode before you commit, free and instant.
Why Rosace Design Studio
The biggest headache in HMO development is coordination. The architectural designer draws something up, then the builder says it cannot be done for the budget, and the planning consultant disagrees with both of them. Meanwhile the mortgage is ticking.
Because we handle architecture, planning and construction in-house, these problems do not arise. We design with buildability and cost in mind from day one. Our construction team prices the job before we submit the planning application, so you know what you are committing to.
We also design interiors that tenants actually want to live in. Good room proportions, decent natural light, proper storage, shared spaces that work. The result is fewer voids, better tenants and stronger yields.
For developers running multiple HMO projects, this model is particularly efficient. We learn your specification preferences, your budget parameters and your letting strategy, and we apply that knowledge across every project without you having to re-explain it each time.
Coverage
Rosace Design Studio works across all of Greater London and within a 30-mile radius. We have completed HMO conversion and extension projects in boroughs including Wandsworth, Hackney, Islington, Camden, Lewisham, Southwark, Lambeth, Newham and Tower Hamlets.
HMO demand varies across London. South London boroughs like Lewisham, Southwark and Lambeth remain popular with developers because of strong transport links and relatively lower purchase prices. East London - particularly Hackney, Newham and Waltham Forest - offers similar opportunities. We are familiar with the planning policies, Article 4 boundaries and licensing requirements in each of these areas.
Outside London, we take on HMO projects across Surrey, Hertfordshire, Essex, Kent and Buckinghamshire, where yields can be strong and planning constraints are often less restrictive.
How It Works
01
Viability Check
You show us the property - or the listing if you have not bought yet. We assess whether it works as an HMO: room sizes, escape routes, access, the licensing picture, and whether planning will be needed.
02
Layout & Planning
We draw up the layouts, including any extensions. Every room is sized to meet HMO standards. We prepare and submit the planning application - whether Article 4 or full permission.
03
Licensing & Building Regs
We coordinate with the council on HMO licensing and produce full building regulations drawings covering fire safety, sound insulation, ventilation and means of escape.
04
Conversion Build
Our in-house construction team delivers the conversion. Building regs, fire safety, sound insulation - all built to the standard the council expects to see at inspection.
Common Questions
