HMO Conversions Isleworth
House to HMO conversions and licence upgrades in Isleworth, fire doors, detection and shared amenities built to the council's licence standards.
- Rated 4.9 from 31 reviews on MyBuilder
- London guide: £40,000 to £75,000
- Free site survey, itemised quote
A new HMO conversion in Isleworth starts with planning, because Hounslow's borough-wide Article 4 Direction removed the right to turn a house into a small HMO from 4 September 2023. Licensing follows: since 11 December 2025, every Isleworth HMO with three or more sharers from two or more households falls within Hounslow's additional scheme. We build the bedrooms, kitchens, bathrooms and fire protection to Hounslow's HMO standards, and the landlord applies for the permission and the licence.
In Isleworth, a light HMO conversion for four to six tenants typically costs £40,000 to £75,000 in construction, or £90,000 to £150,000 with an en-suite to every bedroom (indicative London ranges, Mayfair Studio and LetCompliance, 2026). GS Renovation Ltd, a building contractor based in Potters Bar, does the work in Isleworth: we build the fire doors, detection, bathrooms and kitchens to the council's HMO standards, the landlord applies for the licence, and a registered electrician certifies the electrics.
Price guide
| Work | Indicative range |
|---|---|
| Light HMO conversion, London, 4 to 6 tenants, construction only (Mayfair Studio) | £40,000 to £75,000 |
| Full HMO conversion with en-suites, London, 5 to 6 beds (Mayfair Studio) | £90,000 to £150,000 |
| 5-bed HMO conversion, London and South East (LetCompliance) | £35,000 to £60,000 |
| Fire safety works, typical 5-bed HMO, UK guide (LetCompliance) | £5,000 to £9,500 |
| En-suite added to one bedroom, London (Mayfair Studio) | £3,500 to £8,000 per room |
| Second shared bathroom, UK guide (LetCompliance) | £4,000 to £9,000 |
Indicative ranges from published cost guides (Mayfair Studio and LetCompliance, 2026), not a quotation. Each row names its source and whether it is a London, UK or England-wide figure. Prices checked September 2026.
Quick estimate from published guides
Guide range: choose above
Planning permission for an HMO in Isleworth
Turning an Isleworth house into a small HMO needs planning permission. Nationally, Class L of the General Permitted Development Order 2015 lets a house change from C3 to C4 without an application. Across the whole of Hounslow, an Article 4 Direction confirmed on 8 August 2023 has taken that right away since 4 September 2023. The areas it leaves out are open land, industrial land, Chiswick Business Park, Bedfont Lakes Business Park and the Mogden Sewage Works, so a house on a residential street in Isleworth is covered.
Size sets the next step. In the London Plan glossary, a shared house for three to six people is Use Class C4, while one for more than six falls outside any class as Sui Generis and always needs an application. Class L also does not allow a single house to become two or more separate C4 HMOs. The application for an Isleworth scheme is made by the owner or their agent, with a layout that already meets the room and amenity standards.
Housing in Isleworth
The Council Tax list puts Isleworth at about 13,670 homes, 56% flats against 44% houses; 19% went up before 1919, 21% between the wars and 61% after 1945.
Where Hounslow looks for HMOs, and what it means in Isleworth
Location matters to Hounslow when an HMO needs permission. The council's HMO SPD looks for a PTAL of 4 or better and a walk of no more than 400m to town centre facilities where an HMO needs permission. In Isleworth, being near Isleworth station and the two large neighbourhood centres the Local Plan names, Isleworth and Old Isleworth, helps, but the rating belongs to the exact address and has to be checked.
The London Plan gives the wider context. Policy H9 says boroughs should take account of the role of HMOs in meeting housing needs, and that HMOs of a reasonable standard should generally be protected. For an Isleworth landlord that cuts both ways: a well run, licensed HMO has policy support, while a new one has to justify its location and standard. Get your designer to check transport accessibility before paying for full drawings.
Mandatory and additional HMO licensing in Isleworth
Licensing follows the planning decision. The council designated its additional licensing scheme on 11 September 2025, and from 11 December 2025 it runs across the whole borough. Any section 254 HMO under the Housing Act 2004 is caught once three or more persons from two or more households live there. The mandatory licence applies at five or more occupants in at least two households who share a kitchen, bathroom or toilet.
One exception matters here: a flat in a purpose-built block of three or more self-contained flats falls outside mandatory licensing, although a council's additional scheme can still cover it.
The additional designation ceases on 10 December 2030 unless revoked or extended, so an Isleworth HMO of three or four sharers needs a licence throughout that period. Five years is the usual licence term, cut to a single year where Hounslow has doubts about the management or the condition of the house. The landlord applies for the licence. We build so that the first inspection finds the rooms, facilities and fire protection already in line.
Room sizes, bathrooms and fire safety in an Isleworth HMO
Hounslow's HMO standards set the build. Each room needs 2.14m or more of headroom across 75% of its floor, no more than two people may sleep in one room, and newly provided bathrooms need a mechanical extractor as well as any openable window. In a licensed HMO the council cannot apply discretion, and the national mandatory licence conditions must be met: 6.51 square metres for one adult, 10.22 for two, and no sleeping room under 4.64. In an older Isleworth house, attic and back addition rooms fail first.
Fire safety is the other half. The layout needs a protected escape route, fire doors with closers to the bedrooms and kitchen, an interlinked detection and alarm system, and fire stopping where pipes pass through floors. LACORS housing fire safety guidance is the recognised reference for the level of protection. Sound insulation between lettings matters too, and so does an EPC of at least E for letting, and we fit the insulation and heating controls the energy assessor recommends.
- Interlinked smoke and heat alarms, mains-wired and graded to the council's HMO fire guidance
- Extra shared bathrooms and shower rooms
- Snagging before the council's licence inspection
VOA Council Tax stock of properties, March 2025, for Isleworth & Ivybridge, Syon Green and Spring Grove. Counts rounded by the VOA.
The GS Renovation Difference in Isleworth
An HMO is inspected against a licence, so the details that matter are the ones an officer checks: room heights, extractors, fire doors, alarms and escape routes. We build to the approved layout and to the council's standards for shared housing, and photograph the fire stopping and insulation before they are covered, which helps at the licensing inspection. The landlord or their agent applies for planning and the licence. A registered electrician certifies the alarm and electrical installation.
- One point of contact on the phone, not a call centre
- Kitchens and bathrooms counted against the council's amenity standard
- Detection laid out to the grade the council's HMO fire guidance sets
George always kept to commitments and arrived on time. He offered helpful suggestions during his initial visit and promptly provided a reasonably…
The kitchen has been fitted to the high standard. Saaid was polite, professional, tidy, he pays attention to a little details that make huge…
Saiid did a complete refurbishment of our small bathroom. This involved ripping out the existing bath/shower, basin, toilet, pipework, and tiles and…
FAQ
Frequently Asked Questions about HMO Conversions Isleworth
How much does an HMO conversion cost in Isleworth?
Published figures put a light HMO conversion for four to six tenants at £40,000 to £75,000 in construction, and a full conversion with an en-suite to every bedroom at £90,000 to £150,000 (Mayfair Studio, 2026). A Isleworth house moves within that range with the fire works, the extra bathrooms and the kitchen size. Planning and licence fees are the landlord's and sit outside our quote.
Do you need planning permission to turn an Isleworth house into a small HMO?
Yes. Since 4 September 2023 an Article 4 Direction covering the whole borough has withdrawn the permitted change from a family house to a small shared house. Only open land, industrial areas, two business parks and the Mogden Sewage Works sit outside it, and every residential street in Isleworth is inside it. The owner or their agent makes the application.
Does a three person shared house in Isleworth need a licence?
Yes, where the three sharers are not a single household. Hounslow's additional scheme has covered that size of HMO in every part of the borough since 11 December 2025, and it lasts until 10 December 2030 unless it is revoked or extended first. The landlord applies for the licence; we build to the standards it sets.
How high must rooms be in an Isleworth HMO?
Hounslow's HMO standards ask for 2.14m or more between floor and ceiling across 75% of each room. Where the HMO is licensed, the council has no discretion and the national minimums apply in full. Attic and sloping rooms are where this bites, so check the heights before choosing which rooms become bedrooms.
How long does an HMO licence last in Hounslow?
Five years as a rule. Hounslow shortens that to one year when it is worried about the management or the condition of the house, or where a landlord has deliberately avoided licensing. Hounslow's HMO standards are the yardstick at inspection. A conversion built to the HMO standards from the start avoids condition concerns at the first inspection of an Isleworth property.
Can an Isleworth HMO have seven or more tenants?
Only with planning permission. Above six occupants a shared house leaves Use Class C4, which the London Plan limits to three to six people, and becomes Sui Generis. A large HMO also falls under mandatory licensing, and needs more bathrooms, a bigger kitchen and a stronger fire strategy, so the house has to be large enough before the idea is worth drawing.
What happens if an Isleworth HMO is let without a licence?
The risk is serious. According to GOV.UK, the fine for letting an HMO without a required licence is unlimited, and Hounslow lists financial penalty notices among the possible consequences of licensing breaches. Apply before the tenants move in, and finish the building work first, so the property can be inspected as it will be let.
What fire protection does an HMO conversion need?
An escape route that is protected from fire, self closing fire doors to each bedroom and the kitchen, and a linked smoke and heat detection system, with emergency lighting in larger houses. The LACORS guidance on housing fire safety sets the usual benchmark, and building control checks the escape design. We fit the doors, the fire stopping and the alarm wiring, and the alarm is certified by a registered electrician.
Can two people share a bedroom in a licensed HMO?
Yes, up to a limit of two. Under Hounslow's HMO standards two is the most who may sleep in one room, whatever their ages, and a shared room has to reach 10.22 square metres, the national minimum for two adults. Plan the room mix early, because it sets the number of occupants the licence will allow.
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