Price an HMO conversion or refurbishment the way landlords actually budget it - including the fire-safety and amenity works a standard buy-to-let refurb never has to pay for. Tick the works that apply, adjust any cost for your spec and area, and the tool adds a contingency and shows the cost per square metre. Send the total straight to the BRR calculator.
Property
beds
m²
£
%
Works
Tick what applies. Enter the quantity (or £/m² rate, or cost) in the cell on each row.
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What makes an HMO refurb cost more
An HMO is held to a higher standard than a single-family let, and the gap is almost entirely fire safety and amenity provision. On top of the usual strip-out, rewire, plastering and decoration, an HMO typically needs certified fire doors on every room, interlinked mains alarms throughout, emergency lighting and signage, and often extra bathrooms, en-suites or a second kitchen to meet amenity standards for the number of sharers.
Fire doors (FD30s) to bedrooms and risk rooms - budget around £250 per door fitted, including the closer and intumescent strips.
Interlinked fire detection, emergency lighting and signage to the LACORS/HMO standard - this tool uses an editable per-room allowance.
Amenity standards: enough bathrooms and kitchen provision for the number of lettable rooms - add en-suites or a second bathroom as needed.
A mandatory HMO licence is required for larger HMOs, and many councils run additional or selective licensing - add the council fee as a line.
Worked example - 5-bed HMO conversion
Strip out £1,050; rewire 120 m² x £100 = £12,000; plaster and decorate throughout.
5 fire doors x £250 = £1,250; fire safety to HMO standard 5 rooms x £1,000 = £5,000; two bathrooms and a kitchen; one en-suite £10,000.
On a 120 m² conversion the budget commonly lands well above a like-for-like single-let refurb - the difference is the fire and amenity works.
Licensing, planning and room sizes
Mandatory licensing applies to any HMO let to 5 or more people from 2 or more households; many councils also run additional or selective licensing - check locally.
An Article 4 direction can remove permitted-development rights, so a small (C4) HMO may need planning permission; a large HMO is usually sui generis and needs it.
National minimum bedroom sizes apply - 6.51 m² for one adult and 10.22 m² for two, and a room under 4.64 m² cannot be used to sleep in, which can change the deal.
Treat the total as a planning budget, not a quote, and confirm the fire-safety specification with your local authority - HMO standards vary by council and by the number of storeys and occupants. This is general guidance, not legal or financial advice.
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Frequently asked questions
How much more does an HMO refurb cost than a normal buy-to-let?
The works are the same up to a point - it is the fire-safety package (fire doors, interlinked alarms, emergency lighting, signage) and the extra bathrooms, en-suites or kitchen needed to meet amenity standards that push an HMO higher. This tool itemises those so you can see the difference.
Do I need a licence and planning permission for an HMO?
Most larger HMOs need a mandatory licence (5 or more occupants from 2 or more households), and many areas add additional or selective licensing. Planning depends on the class - a small C4 HMO may be permitted development unless an Article 4 direction applies, while a large HMO is usually sui generis and needs permission. Always check with the local authority.
What fire-safety works does an HMO need?
Typically certified fire doors to bedrooms and risk rooms, an interlinked mains-powered alarm system, emergency lighting on escape routes and signage, with the exact specification set by your council to the LACORS/HMO guidance. Enter your own per-room and per-door costs if you have a quote.
How does this connect to the BRR and GDV tools?
The refurb total feeds the refurb budget in the BRR calculator, and the Property Value Estimator gives you the GDV. Use the buttons to carry the figures across so the three tools work as one HMO deal appraisal.
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Important: BrickCrunch provides general information and estimates only — this is not financial, tax, mortgage or legal advice. Calculations are simplified and your circumstances may differ. UK tax and rate figures are checked against gov.uk (21 June 2026 (2026/27 tax year)) but rates change and errors are possible. Always confirm figures with gov.uk or a qualified professional before making decisions.
