HMO conversion cost calculator
HMO conversions are the most complex — and most scrutinised — refurb deals. Estimate yours below including the fire-safety and licensing items valuers check, then build the full schedule of works with the compliance pack auto-included.
How to cost an HMO conversion
- 1Size the works to the rooms
Each lettable room carries a share of strip-out, layout reconfiguration, electrics, plastering and decoration. Add en-suites per room where the market supports it.
- 2Add the compliance pack
Fire doors to every bedroom plus communal and escape-route doors, a fire alarm to the correct grade, emergency lighting on 3+ storeys, a fire risk assessment, signage and an EICR.
- 3Size the kitchen to occupancy
Councils set minimum kitchen facilities per sharer — extra units, worktop, hob rings and fridge/freezer capacity. Budget for a larger kitchen than a standard BTL.
- 4Include licensing and contingency
Add the HMO licence fee (varies by council) and a 15% contingency for the unforeseen — HMO conversions carry more structural and compliance surprises than a plain refurb.
The difference between a profitable HMO and a stalled one is usually the items investors forget to budget: the jump from a Grade D1 to a Grade A alarm on a three-storey property, the fire-stopping and compartmentation behind the walls, the en-suite drainage runs, and the council’s kitchen amenity standards. These aren’t optional extras — a valuer or licensing officer will expect them, and a lender wants them costed.
ScopeWise auto-includes the full HMO compliance pack and warns you if any mandatory category is missing, so nothing falls through. Remember the prompts are guidance — HMO standards vary by authority, so confirm the detail with your council before you rely on the numbers.
Typical HMO compliance & conversion items
| Item | Indicative cost | Driver |
|---|---|---|
| FD30(S) fire door (fitted) | £320–£650 each | Per bedroom + communal/escape |
| Fire alarm — Grade D1 (small HMO) | £900–£1,600 | Mains interlinked, ≤6 occupants |
| Fire alarm — Grade A (3+ storey) | £3,500–£6,000 | Panel, sounders, certified |
| Emergency lighting | £80–£180/fitting | Escape routes, 3+ storeys |
| En-suite shower room | £2,200–£4,500 each | Per room |
| HMO kitchen (occupancy-sized) | £3,500–£8,000 | Per kitchen |
| Fire risk assessment | £150–£500 | Per property |
| HMO licence fee | £500–£1,600 | Per council (5-year licence) |
Indicative figures — HMO standards and fees vary by local authority. Confirm with your council.
Frequently asked questions
How much does it cost to convert a house to an HMO?+
As a rough guide, a typical 5–6 bed HMO conversion runs from around £40,000 to £100,000+ depending on the starting condition, number of en-suites, storeys (which drives the alarm grade) and region. Use the calculator above for a figure tailored to your property, then build the itemised schedule.
What fire safety do I need for an HMO?+
Generally: FD30(S) fire doors to bedrooms, kitchen and the protected escape route; an interlinked fire detection system to the right grade (Grade D1 for smaller HMOs, Grade A for larger/3+ storey under BS 5839-6); emergency lighting where escape routes lack borrowed light; fire-stopping/compartmentation; signage, a kitchen fire blanket and extinguishers; and a fire risk assessment. Your council's standards govern the detail.
Do I need planning permission for an HMO?+
A small HMO (up to 6 occupants, use class C4) is often permitted development from C3 — but many councils have an Article 4 Direction removing that right, meaning you need planning permission. Larger HMOs (sui generis) usually need planning. Always check your council and any Article 4 area.
When do I need an HMO licence?+
Mandatory licensing applies to HMOs with 5 or more occupants forming 2 or more households. Many councils also run additional or selective licensing covering smaller HMOs. Fees and conditions vary by authority.
What is the minimum room size for an HMO?+
Under national mandatory-licensing rules in England, a room slept in by one adult must be at least 6.51 m², and by two adults at least 10.22 m²; rooms under 4.64 m² can't be used for sleeping. Councils can (and often do) set higher local standards, so always check the specific authority.
How many bathrooms does an HMO need?+
A common council standard is roughly one bathroom/WC per 3–5 sharers, but it varies by authority and is one reason en-suites per room are popular — they raise the amenity ratio and the rent. Confirm the ratio your council requires.
Is an HMO more profitable than a single let?+
Usually yes on cash flow — multiple rents from one building typically beat a single AST — but the conversion cost, compliance, licensing and management are all higher, and refinance valuations can be treated differently. Model the full cost (including the compliance pack) and the exit before committing.
Related tools & guides
Want to know how these figures are calculated? See our cost methodology.
Cost figures shown are indicative estimates, not quotations. You are responsible for verifying all costs (obtain contractor quotes) and any figures submitted to a lender. ScopeWise is a documentation tool, not financial, tax, structural or planning advice. HMO compliance prompts are guidance only — confirm requirements with your local council, as standards and licensing vary by authority.