Do You Need Planning Permission to Convert a House into Flats?
Yes. Converting a house into flats requires full planning permission in England. There is no permitted development route. Here is what the application involves, what it costs, and what councils look for.
TL;DR - The Quick Answer
Converting a house (Use Class C3) into multiple self-contained flats requires a full planning application. There is no permitted development shortcut. The previous government proposed a PD right to split houses into two flats in the 2023 Autumn Statement, but no consultation was published before the general election and the current Labour government has not taken the proposal forward. As of April 2026, you need planning permission for every house-to-flats conversion. Application fees are £610 per additional dwelling created. Councils will assess parking, bin and cycle storage, amenity space, noise impact, and whether each flat meets the Nationally Described Space Standards. You will also need separate building regulations approval covering fire safety, sound insulation, and means of escape.
Why You Need Full Planning Permission
A single house and a block of flats are both in Use Class C3 (dwellinghouse) under the Town and Country Planning (Use Classes) Order 1987. But splitting one C3 dwelling into multiple C3 dwellings is a material change of use that requires planning permission. The General Permitted Development Order (GPDO) does not include a class that allows this conversion. More information about converting a house to flats on the Planning Portal.
This applies everywhere in England regardless of the size of the house, the number of flats proposed, or whether you are adding any floor area. Even a straightforward internal subdivision with no external changes requires a planning application.
The reason is straightforward: multiple households in one building creates different impacts from a single household. More residents means more cars, more bins, more noise, and different demands on local services. The planning system requires councils to assess those impacts before granting permission.
Important: Do not confuse flat conversions with HMOs (Houses in Multiple Occupation). Converting to an HMO for 3-6 people sharing facilities is a different use class (C4) and does benefit from permitted development in some areas. Flat conversions create self-contained dwellings with their own front doors, kitchens, and bathrooms - that is a different proposition entirely.
The Proposed Permitted Development Right
In the Autumn Statement 2023, Chancellor Jeremy Hunt announced a new permitted development right that would allow homeowners to split a house into two self-contained flats without needing planning permission. The government said it would consult in early 2024 and implement the change during 2024.
That consultation never happened. The general election in July 2024 brought a change of government, and the incoming Labour administration has not taken the proposal forward. As of April 2026, there has been no consultation, no draft legislation, and no indication that this PD right will be introduced.
The proposed PD right would have been subject to conditions - likely a prior approval process where councils could still assess transport, noise, and design impacts. It would probably not have applied in conservation areas, to listed buildings, or to flats above a certain floor area threshold. But since no consultation was published, the detail remains speculation.
Timeline of the Proposed PD Right
- 1Nov 2023: Autumn Statement announces intention to introduce PD right for house-to-2-flat conversions
- 2Early 2024: Consultation promised - never published
- 3Jul 2024: General election - Labour government takes office
- 4Apr 2026: No further action taken. Full planning permission still required.
Bottom line: Do not wait for a PD right that may never come. If you want to convert a house to flats, you need to apply for planning permission under the current rules.
What the Council Assesses
When you submit a planning application to convert a house into flats, the council will assess the proposal against local plan policies covering residential conversions. The key issues are consistent across most councils:
Key Assessment Criteria
- Flat sizes: Each unit must meet or exceed the Nationally Described Space Standards (NDSS) where adopted by the council. Most London boroughs and many other authorities enforce NDSS.
- Parking: Many councils require a parking survey to demonstrate that existing on-street capacity can absorb the additional demand. Some require off-street parking per unit.
- Bin and recycling storage: Each flat needs separate bin provision. Bin stores must be shown on drawings, typically within 25m of the highway collection point.
- Cycle storage: Secure, covered cycle storage is expected for each unit - typically 1 space per 1-bed flat and 2 spaces per 2-bed or larger.
- Amenity space: Councils expect outdoor space for residents - private gardens, balconies, or shared communal gardens. Ground floor flats without access to any outdoor space are harder to get approved.
- Noise and overlooking: Flat layouts should minimise noise transfer between units and avoid creating new overlooking to neighbouring properties. Bedrooms above living rooms are a common reason for objection.
- Character of the area: In streets dominated by family houses, councils may resist flat conversions to protect neighbourhood character. Some local plans have specific policies limiting conversions in certain areas.
Tip: Before spending money on drawings, check your council's local plan for specific flat conversion policies. Some boroughs (like Haringey and Thanet) publish dedicated guidance notes for house-to-flat conversions that spell out exactly what they expect.
Planning Application Costs and Timeline
The application fee for a house-to-flats conversion depends on how many new dwellings you are creating. From 1 April 2026, fees are indexed to CPI (3.8% increase over 2025 rates).
| Conversion | New dwellings created | Application fee (from Apr 2026) |
|---|---|---|
| House to 2 flats | 1 additional | £610 |
| House to 3 flats | 2 additional | £1,220 |
| House to 4 flats | 3 additional | £1,830 |
| House to 5+ flats | 4+ additional | £610 per additional dwelling |
The fee is calculated on the number of additional dwellings, not the total. Converting a house into two flats creates one additional dwelling, so the fee is £610. Converting into four flats creates three additional dwellings: £1,830. Source: Planning Portal fee schedule (April 2026).
Other Costs
- Architect/designer: £2,000-8,000 for planning drawings and design work, depending on complexity
- Parking survey: £300-800 if required by the council
- Pre-application advice: £100-600 depending on the council (strongly recommended)
- Building regulations: £800-2,500 for building control fees (separate from planning)
- Structural engineer: £500-2,000 if internal walls are being removed or floors altered
Timeline
A minor planning application (which flat conversions fall under) has a target determination period of 8 weeks. In practice, flat conversion applications often take 8-13 weeks because they require consultation with highways, environmental health, and sometimes the council's housing standards team.
Add 4-8 weeks for pre-application advice before you submit, plus 6-12 weeks for building regulations drawings afterwards. From first instruction to starting work on site, expect 5-8 months.
| Cost item | Typical range | Notes |
|---|---|---|
| Planning application fee | £610 per additional dwelling | CPI-indexed annually from April 2025 |
| Architect/designer | £2,000-8,000 | Planning drawings and design work |
| Pre-application advice | £100-600 | Varies by council; strongly recommended |
| Parking survey | £300-800 | If required by local policy |
| Building control fees | £800-2,500 | Separate from planning; covers inspections |
| Structural engineer | £500-2,000 | If internal walls removed or floors altered |
Source: Planning Portal, Mayfair Studio project data • Data as of 2026
Minimum Flat Sizes (NDSS)
The Nationally Described Space Standards (NDSS) set minimum gross internal areas for new dwellings, including those created by conversion. NDSS is not mandatory nationally - each council must adopt it through their local plan. However, most London boroughs and many other authorities enforce NDSS as a planning policy requirement. Source: GOV.UK: Technical housing standards.
| Flat type | Occupancy | Minimum GIA (single storey) |
|---|---|---|
| Studio | 1 person | 37 sqm (shower room) / 39 sqm (bathroom) |
| 1-bed flat | 2 persons | 50 sqm |
| 2-bed flat | 3 persons | 61 sqm |
| 2-bed flat | 4 persons | 70 sqm |
| 3-bed flat | 5 persons | 86 sqm |
Each flat also needs built-in storage (1.0 sqm for a studio, 1.5 sqm for a 1-bed, 2.0 sqm for a 2-bed, 2.5 sqm for a 3-bed), and bedrooms must meet minimum floor areas: 11.5 sqm for a double bedroom and 7.5 sqm for a single bedroom.
Practical implication: A typical 3-bed Victorian terraced house of about 90-100 sqm might only be large enough for two 1-bed flats (50 sqm each) once you account for hallways, staircases, and shared areas. Get accurate floor area measurements before committing to a layout.
CIL and Section 106
The Community Infrastructure Levy (CIL) is a charge that councils levy on new development to fund local infrastructure. Whether your flat conversion is liable for CIL depends on whether you are adding new floor area.
No CIL Liability
- Pure internal subdivision with no new floor area
- Converting existing residential floor area (C3 to C3)
Potentially CIL Liable
- Any new-build extensions added to facilitate the conversion
- Conversion of non-residential parts (garage, outbuilding) to residential
CIL rates vary by council. In London, you pay both the borough CIL and the Mayor of London CIL. Rates range from £0 to over £400 per sqm depending on location.
Section 106 agreements are less common for small flat conversions but can apply if the council's local plan requires affordable housing contributions from conversions creating a certain number of units. In London, affordable housing obligations typically kick in at 10 or more units, so most house-to-flat conversions are below the threshold. Check your council's specific policies. More information on CIL from GOV.UK.
Building Regulations for Flat Conversions
Planning permission and building regulations are separate approvals. Even after you get planning permission, you need building regulations sign-off before the flats can be occupied. The key areas are:
Fire Safety (Approved Document B)
Fire safety is the most complex part of a flat conversion. Requirements include:
- 30-minute fire resistance for all elements separating flats (floors, walls, doors)
- Protected escape routes - a fire-rated corridor and staircase from each flat to a final exit. This often requires fire-rated doors (FD30S) and upgrading the existing staircase.
- Mains-powered interlinked smoke alarms on every level within the escape route, plus heat detectors in kitchens
- Emergency egress windows for habitable rooms where alternative escape is not available (minimum 0.33 sqm clear opening)
Sound Insulation (Approved Document E)
Separating floors and walls between flats must achieve minimum sound insulation performance. For conversions (as opposed to new builds), the standards are:
- Airborne sound: Minimum 43 dB for walls and floors between flats (lower than the 45 dB required for new builds)
- Impact sound: Maximum 64 dB for floors between flats
- Pre-completion testing is required - an acoustic consultant must test the separating elements before sign-off
In practice, this usually means adding independent ceiling systems, resilient bars, acoustic insulation between joists, and floating floors. Budget £5,000-15,000 for sound insulation work depending on the building.
Other Building Regulations
- Part L (Conservation of fuel and power): Thermal upgrades may be required where fabric is exposed during works
- Part M (Access): Ground floor flats should be accessible. Entrance widths, level thresholds, and accessible bathrooms may be required.
- Part P (Electrical): Each flat needs its own consumer unit and separate metering
- Part G (Water): Separate hot/cold water systems and drainage for each flat
Converting a house into flats in England requires full planning permission - there is no permitted development route. The proposed PD right to split a house into 2 flats (2023 Autumn Statement) was never consulted on and has not been taken forward by the current government. Application fee: £610 per additional dwelling (from 1 April 2026). Councils assess parking, bin/cycle storage, amenity space, noise, and minimum flat sizes (NDSS). Building regulations approval is needed separately for fire safety (30-min resistance, protected escape), sound insulation (43 dB airborne, 64 dB impact), and means of escape. Pure internal subdivision with no new floor area is exempt from CIL.
Frequently Asked Questions
Do I need planning permission to convert a house into flats?
Yes. Converting a house into flats (whether two flats or more) requires a full planning application in England. There is no permitted development route for this type of conversion. This applies even if you are only making internal changes and not altering the external appearance of the building. The application fee is £610 per additional dwelling created (from 1 April 2026). Source: Planning Portal.
How much does it cost to convert a house into flats?
Planning application fees are £610 per additional dwelling from April 2026 (so £610 for a house-to-2-flats conversion, £1,220 for house-to-3-flats). Total project costs including architect fees (£2,000-8,000), building regulations (£800-2,500), structural engineer (£500-2,000), and construction work vary widely. Construction costs for internal conversion work typically range from £800-1,500 per sqm depending on the extent of work, with sound insulation and fire safety upgrades adding £5,000-15,000. A straightforward 2-flat conversion of a 3-bed terraced house might cost £40,000-80,000 in total construction.
Can I convert a house into flats without planning permission using permitted development?
No. There is no permitted development right for converting a house into flats. The previous Conservative government proposed a PD right for house-to-2-flat conversions in the 2023 Autumn Statement, but the consultation was never published, and the current Labour government has not taken the proposal forward. As of April 2026, full planning permission is required. Do not confuse this with HMO conversions (houses in multiple occupation), which have a separate permitted development route in some areas under Use Class C4.
What is the minimum size for a flat conversion?
Where the Nationally Described Space Standards (NDSS) apply - which includes most London boroughs and many councils across England - the minimum sizes are: studio flat 37-39 sqm, 1-bed 2-person flat 50 sqm, 2-bed 3-person flat 61 sqm, 2-bed 4-person flat 70 sqm. Double bedrooms must be at least 11.5 sqm and single bedrooms at least 7.5 sqm. Each flat also needs minimum 1.5 sqm of built-in storage. Check whether your council has adopted NDSS in their local plan. Source: GOV.UK: Technical housing standards.
Do I need to pay CIL on a house-to-flats conversion?
If you are only subdividing existing residential floor area with no new-build extensions, CIL is not payable. The exemption applies because you are converting existing C3 (residential) floor area. However, if your conversion includes new extensions or converts non-residential space (such as a garage or outbuilding) into residential use, the net additional floor area may be CIL liable. CIL rates vary by council - in London you pay both the borough CIL and the Mayor of London CIL.
What building regulations apply to flat conversions?
The main requirements are: Approved Document B (fire safety) - 30-minute fire resistance for separating elements, protected escape routes with FD30S fire doors, mains-powered interlinked smoke alarms; Approved Document E (sound insulation) - minimum 43 dB airborne and maximum 64 dB impact for separating floors and walls, with pre-completion acoustic testing required; Approved Document L (thermal performance); Approved Document M (accessibility for ground floor flats); and Approved Document P (separate electrical installations per flat). Sound insulation and fire safety work typically adds £5,000-15,000 to conversion costs.
How long does planning permission take for a house-to-flats conversion?
The statutory target is 8 weeks for a standard planning application. In practice, house-to-flat conversion applications take 8-13 weeks because they involve consultation with highways, environmental health, and sometimes housing standards officers. Pre-application advice (recommended) adds 4-8 weeks before submission. Building regulations drawings and approval add another 6-12 weeks after planning permission is granted. Total timeline from first instruction to starting work on site: 5-8 months.
Will neighbours be consulted on my flat conversion application?
Yes. The council will notify immediate neighbours and usually erect a site notice. Common objections to flat conversions include increased parking pressure, more bins on the street, noise from additional residents, and loss of family housing. Your application is stronger if you can demonstrate adequate parking (via a parking survey), proper bin and cycle storage, and that the flats meet minimum space standards.
Summary
Converting a house into flats is a viable development route, but it requires full planning permission, building regulations approval, and careful attention to minimum space standards. There is no permitted development shortcut.
The most common reasons for refusal are undersized flats, inadequate parking or bin storage, and poor internal layouts that create noise issues between units. Get these right from the start and your application has a strong chance.
Before committing to a layout: measure the existing floor area accurately, check your council's specific conversion policies, and consider pre-application advice. A few hundred pounds on pre-app can save thousands in design revisions or a refusal.
Related Articles
Converting a house to flats in England requires full planning permission. There is no permitted development route - the proposed PD right from the 2023 Autumn Statement was never implemented. Application fee: £610 per additional dwelling (April 2026). Minimum flat sizes under NDSS: 1-bed 50 sqm, 2-bed 61-70 sqm. Councils assess parking, bin/cycle storage, amenity space, noise, and area character. Building regulations require 30-minute fire resistance, protected escape routes, acoustic testing (43 dB airborne), and separate electrical installations per flat. Pure internal subdivision is CIL exempt. Timeline: 8-13 weeks for planning, 5-8 months total to site start. Mayfair Studio handles house-to-flat conversion applications from £1,295.
Frequently Asked Questions
Do you need planning permission to split a house into flats in the UK?
Yes, full planning permission is required to split a house into flats in England. There is no permitted development right for this conversion. The application fee is £610 per additional dwelling created (from 1 April 2026). Councils assess flat sizes against NDSS (minimum 50 sqm for a 1-bed flat), parking provision, bin and cycle storage, amenity space, and impact on neighbourhood character. Timeline: 8-13 weeks for determination. Building regulations approval is also needed for fire safety, sound insulation, and means of escape.
How much does planning permission cost for a house to flats conversion?
The planning application fee is £610 per additional dwelling from 1 April 2026 (CPI-indexed annually). Converting a house into 2 flats costs £610 (1 additional dwelling). Converting into 3 flats costs £1,220 (2 additional). Other costs: architect £2,000-8,000, pre-application advice £100-600, parking survey £300-800 if required. Total professional fees before construction: £3,000-12,000 depending on complexity. Mayfair Studio offers fixed-fee planning packages for flat conversions from £1,295.
What are the building regulations for converting a house into flats?
Key building regulations for flat conversions: Approved Document B (fire safety) requires 30-minute fire resistance for separating elements, protected escape routes with FD30S fire doors, and mains-powered interlinked smoke alarms. Approved Document E (sound) requires minimum 43 dB airborne and maximum 64 dB impact sound insulation between flats, with pre-completion acoustic testing. Part L covers thermal performance, Part M covers accessibility (ground floor), Part P requires separate electrical installations per flat. Sound insulation and fire safety work typically costs £5,000-15,000.
Is there a permitted development right to convert a house into 2 flats?
No. The 2023 Autumn Statement proposed a new PD right allowing houses to be split into 2 flats, but no consultation was ever published. The July 2024 change of government means this proposal has effectively stalled. As of April 2026, full planning permission is still required for all house-to-flat conversions in England, regardless of the number of flats proposed.
What is the minimum size for a converted flat in the UK?
Under the Nationally Described Space Standards (NDSS), minimum gross internal areas are: studio 37-39 sqm, 1-bed 2-person flat 50 sqm, 2-bed 3-person flat 61 sqm, 2-bed 4-person flat 70 sqm, 3-bed 5-person flat 86 sqm. Double bedrooms minimum 11.5 sqm, single bedrooms 7.5 sqm, with 1.5 sqm built-in storage per flat. NDSS applies where adopted by the local council through their local plan - most London boroughs and many other authorities enforce it.
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