HMO Conversion Builders: What Should Landlords Look For?
28, Sep, 2026
Six bedrooms, a good location, and strong rental demand can make the numbers look attractive. Then it raises a real question: Are the bedrooms large enough? Will the property need new bathrooms? Does the postcode have planning restrictions? What about fire safety, electrics and plumbing?
Choosing the right HMO conversion builders matters because converting a house is more than adding walls and bedrooms. The layout, structure, safety measures, and finish must work together before the property is tenant-ready.
Start With the Property
One of the biggest mistakes is deciding how many bedrooms to create before checking what the property can support.
A room might look large enough on a floor plan but lose usable space because of a chimney breast, sloping ceiling, or awkward layout. Adding more rooms might also leave too little shared space or make the property difficult to use.
A proper HMO conversion should look at the whole property first. This includes the existing layout, structure, stairs, windows, plumbing routes, kitchen, bathrooms, and available space.
Does Your Property Need HMO Planning Permission?
In Merton, for example, permitted development rights have been removed for converting homes from C3 to small HMOs in all wards. This means a new small HMO conversion in Merton needs planning permission. The borough-wide controls came into effect on 24 March 2026. Planning permission and HMO licensing are separate matters. A property might need planning permission and still need an HMO licence before it is occupied.
What Should HMO Conversion Builders Handle?
An HMO conversion often involves several types of building work at the same time. Depending on the property, this might include:
Changing the internal layout
Creating or removing walls
Adding bathrooms or en-suites
Upgrading plumbing and electrics
Improving fire safety
Reworking kitchens and shared areas
Adding fire doors and other safety measures
Improving heating and ventilation
Carrying out structural work
Decorating and finishing the property
Denham Crescent provides architectural, structural, refurbishment and construction services as part of an integrated approach, covering the project from feasibility and design through to construction. Its structural team also works on foundations, alterations and existing buildings.
Room Sizes and Fire Safety Need Early Attention
Merton's current HMO guidance states that a bedroom for one person over 10 must have at least 6.51m² of usable floor space. A room for two people over 10 needs at least 10.22m². Only floor space where the ceiling is higher than 1.5 metres counts.
There are other requirements too. HMOs need suitable fire precautions and escape routes, enough kitchens, bathrooms and toilets for the number of occupants, and enough living space to avoid overcrowding. These details should be considered whilst the layout is being planned, not after the building work has started.
How Much Does an HMO Conversion Cost?
A property needing new bedrooms, bathrooms, plumbing, electrics and fire safety upgrades will cost more than one needing mainly cosmetic work. The condition of the property also matters. Older houses might need more work to the wiring, plumbing, heating, insulation or structure.
Adding several bathrooms can also increase costs because new water and waste pipe routes might be needed. The best way to compare HMO conversion costs is to ask for a detailed quotation. It should show what is included rather than giving you one figure without explaining the work behind it.
What Should Be Included in Your Builder's Quote?
A cheap quote can become expensive if important work has been left out. Before choosing an HMO conversion contractor, check whether the quotation covers the full scope of work. This might include demolition, structural changes, plumbing, electrical work, bathrooms, kitchen work, fire safety measures, doors, flooring, decorating, waste removal and final finishing.
Also ask who will coordinate the different trades. This matters because an HMO refurbishment often involves several teams working in the same property. Plumbing needs to work with the bathroom layout. Electrical work needs to work with the room layout. Structural changes need to be planned before walls are removed.
Look for Building Experience, Not Only HMO Claims
Look at the projects it has completed and the type of work involved. Experience with structural changes, complete refurbishments, plumbing, electrics, kitchens and bathrooms gives you useful evidence of how a builder handles projects with several moving parts.
Denham Crescent has completed refurbishment projects involving multiple trades. In one Mitcham project, the work included plumbing, electrical work, built-in wardrobes, a driveway, a new kitchen and a further extension. Client Theran Bhatia also said the company had renovated and extended two of his properties and praised its quality, service and cost control.
Another Denham project in Croydon combined a three-metre rear extension with a complete ground-floor refurbishment, including new electrics, plumbing, a bathroom and kitchen, with the work approved by the Building Control Officer.
Five Questions to Ask Before Hiring an HMO Builder
Before starting an HMO conversion, ask:
Can you assess whether the existing property suits the planned layout?
What building work is included in the quotation?
Who will handle structural, electrical, and plumbing work?
How will fire safety and other required standards be addressed?
What happens if unexpected problems are found after work starts?
Choose HMO Conversion Builders With the Whole Property in Mind
A successful HMO conversion needs more than extra bedrooms. The property needs a sensible layout, suitable room sizes, safe escape routes, working bathrooms and kitchens, reliable services and the right approvals.
The right HMO conversion builders should help identify these issues before construction begins, giving you a clearer idea of the work and costs involved.
For landlords planning an HMO conversion in South West London, Denham Crescent provides structural, refurbishment, architectural and construction services, helping property owners manage complex building work from the early stages through to completion.
Share:
