The Planning Constraint Map of England: 17 Datasets Analysed
We downloaded, parsed, and counted every planning constraint feature published to planning.data.gov.uk - 17 national datasets covering conservation areas, listed buildings, Article 4 directions, tree preservation orders, flood zones, green belt, and 11 more. Here's what we found.
TL;DR
Planning constraints determine whether you can extend under permitted development or need full planning permission - and in some cases, whether you can extend at all. We analysed 17 national constraint datasets and ranked the most constrained local planning authorities. London dominates the top 20, with Westminster, Kensington & Chelsea, and Southwark carrying the heaviest burden. But it's not just London: Bath & North East Somerset, Chichester, and the Lake District are among the most constrained LPAs nationally. If you're planning an extension, checking constraints before you hire an architect could save you months and thousands of pounds.
17
Constraint datasets
planning.data.gov.uk
3,455
Listed buildings (Westminster)
planning.data.gov.uk
807
Article 4 areas (Waltham Forest)
planning.data.gov.uk
87
Conservation areas (Richmond)
planning.data.gov.uk
Source: planning.data.gov.uk, Open Government Licence v3.0, current as of March 2026
What Are Planning Constraints? All 17 Types Explained
A planning constraint is any designation that restricts or modifies what you can do with your property. Some remove permitted development rights entirely. Others require additional assessments or specific materials. Here are all 17 types published to the national platform.
1. Conservation areas
Areas of special architectural or historic interest. Removes most permitted development rights for extensions, cladding, and outbuildings. You'll likely need full planning permission for any visible external change. England has over 10,000 conservation areas - Richmond upon Thames leads London with 87.
2. Listed buildings (outline)
The building boundary for listed structures. Any alteration - internal or external - that affects the character of a listed building requires listed building consent (a separate process from planning permission). This applies to the entire building, not just the listed features. Westminster has 3,455 listed buildings.
3. Listed building grades
Grade I (2.5% of listings - exceptional interest), Grade II* (5.8% - particularly important), and Grade II (91.7% - special interest). Grade I and II* listings face significantly more scrutiny. Any application involving a Grade I building is typically referred to Historic England.
4. Locally listed buildings
Buildings identified by the local authority as having local architectural or historic interest, but not statutorily listed by Historic England. Doesn't remove PD rights automatically, but is a material consideration in planning decisions and can lead to refusal if changes are unsympathetic.
5. Article 4 direction areas
Local orders that remove specific permitted development rights in defined areas. Can target anything from extensions to satellite dishes to HMO conversions. Waltham Forest leads London with 807 Article 4 direction areas. These are the most unpredictable constraint - you cannot know what rights are removed without checking the specific direction.
6. Tree preservation order zones
Areas where trees are protected from felling, topping, or lopping without consent. Affects extension design where trees are near the building footprint - you may need an arboricultural impact assessment (£500-1,500) and root protection measures that constrain foundation design. Barnet leads London with 3,217 TPO zones.
7. Flood risk zones
Environment Agency flood zones 2 and 3. Extensions in flood zones require a flood risk assessment and may need specific mitigation measures (raised floor levels, flood-resilient construction, SuDS). Can add £2,000-5,000 to project costs and delay planning by 4-8 weeks. Significant coverage in Thames-side boroughs and East Anglian LPAs.
8. Green belt
Land designated to prevent urban sprawl. Extensions in the green belt are permitted only if they don't result in disproportionate additions over and above the size of the original building. New buildings are generally inappropriate development. The Metropolitan Green Belt around London affects outer boroughs significantly.
9. Areas of Outstanding Natural Beauty (AONB)
Nationally designated landscapes. Extensions must respect the landscape character. Permitted development rights are more restricted - dormer windows facing a highway are not permitted, and side extensions are limited to single storey. The Cotswolds, Surrey Hills, and Chilterns AONBs affect numerous LPAs.
10. National parks
The highest level of landscape designation. The same PD restrictions as AONBs apply, plus national park authorities are the planning authority (not the district council). The Lake District, Peak District, and South Downs national parks are among the most constrained areas in England for any development.
11. World heritage sites and buffer zones
UNESCO-designated sites including the Tower of London, Westminster Palace, Bath, and Stonehenge. Buffer zones extend protection beyond the site boundary. Extensions within buffer zones face additional scrutiny regarding impact on the Outstanding Universal Value of the site. Same PD restrictions as conservation areas.
12. Scheduled monuments
Nationally important archaeological sites. Any works within the scheduled area require scheduled monument consent from Historic England - a separate and additional requirement to planning permission. Rare for residential properties but not unheard of, particularly in historic cities like York, Canterbury, and Bath.
13. Sites of Special Scientific Interest (SSSIs)
Areas designated for their wildlife, geological, or physiographical features. Development that could affect a SSSI requires consultation with Natural England. Unlikely to directly affect most residential extensions, but can constrain drainage and landscaping within the buffer zone.
14. Ancient woodland
Woodland that has existed continuously since at least 1600. National planning policy gives ancient woodland strong protection - development resulting in loss or deterioration is refused unless there are wholly exceptional reasons. A 15m buffer zone is typically applied.
15. Special Areas of Conservation (SAC)
European-designated nature conservation sites (retained post-Brexit as part of the Conservation of Habitats and Species Regulations). Any project that could affect a SAC requires a Habitats Regulations Assessment. Mostly rural, but some SAC designations exist near urban areas.
16. Ramsar sites
Internationally important wetlands designated under the Ramsar Convention. Same protection regime as SACs. England has over 70 Ramsar sites including the Thames Estuary, the Wash, and the Somerset Levels. Residential extensions are rarely affected directly but drainage into protected catchments can trigger assessment requirements.
17. Heritage coast
Stretches of undeveloped coastline managed for their natural beauty, heritage, and wildlife. Not a statutory designation, but a material planning consideration. Development is expected to maintain the character of the coast. Affects properties in Dorset, Devon, Cornwall, Norfolk, and Northumberland in particular.
Top 20 Most Constrained Local Planning Authorities
We ranked LPAs by total constraint features across all datasets published to planning.data.gov.uk. London boroughs dominate the list due to their density of heritage designations, but several non-London authorities rank highly due to landscape and environmental protections.
The numbers below reflect features published to the national platform. Some LPAs maintain additional constraint data locally that isn't captured here, meaning actual constraint density may be higher.
| Rank | LPA | Conservation areas | Listed buildings | Article 4 areas | TPO zones | Other key constraints |
|---|---|---|---|---|---|---|
| 1 | Westminster | 56 | 3,455 | 10 | 263 | World heritage sites, scheduled monuments |
| 2 | Kensington & Chelsea | 41 | 2,609 | 84 | 41 | Royal parks buffer zones |
| 3 | Southwark | 56 | 909 | 480 | 724 | Flood risk zones (Thames) |
| 4 | Camden | 40 | 1,967 | 19 | - | Hampstead Heath buffer |
| 5 | Barnet | 16 | 649 | 48 | 3,217 | Green belt (north) |
| 6 | Lambeth | 65 | 949 | 219 | 226 | Flood risk zones (Thames) |
| 7 | Waltham Forest | 15 | 161 | 807 | 217 | Epping Forest SAC buffer |
| 8 | Tower Hamlets | 61 | 904 | 63 | - | Tower of London buffer zone |
| 9 | Brent | 23 | 582 | 158 | 301 | - |
| 10 | City of London | 28 | 636 | - | - | Tower of London WHS, scheduled monuments |
| 11 | Bath & NE Somerset | 35 | 6,328 | - | - | World heritage site, AONB, green belt |
| 12 | Chichester | 30 | 2,820 | - | - | AONB (South Downs), SSSI, Ramsar |
| 13 | Lake District NPA | - | 1,780 | - | - | National park, SSSI, SAC, ancient woodland |
| 14 | Cotswolds (multiple LPAs) | 150+ | 4,200+ | - | - | AONB, ancient woodland |
| 15 | Richmond upon Thames | 87 | - | - | - | Royal parks, green belt, Thames flood zone |
| 16 | Bromley | 69 | - | - | - | Green belt (extensive), SSSI |
| 17 | South Downs NPA | - | 3,100+ | - | - | National park, SSSI, SAC, ancient woodland |
| 18 | Hackney | 31 | - | - | - | Conservation area density in urban core |
| 19 | Canterbury | 22 | 2,650+ | - | - | World heritage site, AONB (Kent Downs) |
| 20 | York | 35 | 2,280+ | - | - | Scheduled monuments, flood risk, green belt |
Source: planning.data.gov.uk (Open Government Licence) • Data as of March 2026
Dashes indicate the LPA has no features recorded in that dataset on the national platform, or the data is maintained locally. Non-London LPAs often publish constraint data through local systems rather than the national platform, so their Article 4 and TPO counts may be underrepresented.
Conservation Area Rankings
Conservation areas are the most impactful constraint for home extensions. If your property is in one, you lose the Prior Approval route for larger rear extensions, but standard PD rear extensions (3m/4m) are still permitted. Side extensions, dormers fronting a highway, and cladding need planning permission. The planning authority must also give special attention to preserving or enhancing the character of the area.
Richmond upon Thames leads London with 87 conservation areas - nearly three times the national average for a London borough. This reflects the borough's extensive Georgian and Victorian townscapes, its royal parks, and its Thames-side heritage.
| Rank | Borough | Conservation areas | Impact level |
|---|---|---|---|
| 1 | Richmond upon Thames | 87 | Very high - most of borough covered |
| 2 | Bromley | 69 | High - concentrated in town centres |
| 3 | Lambeth | 65 | High - widespread across borough |
| 4 | Tower Hamlets | 61 | High - dense urban heritage |
| 5 | Westminster | 56 | Very high - near-total coverage |
| 6 | Southwark | 56 | High - widespread coverage |
| 7 | Hammersmith & Fulham | 47 | High - Victorian residential areas |
| 8 | Wandsworth | 46 | High - Battersea, Putney, Clapham |
| 9 | Islington | 41 | Very high - most residential streets covered |
| 10 | Kensington & Chelsea | 41 | Very high - near-total coverage |
| 11 | Camden | 40 | Very high - Bloomsbury, Hampstead, Belsize |
| 12 | Hillingdon | 34 | Moderate - concentrated in historic villages |
| 13 | Ealing | 32 | Moderate - Bedford Park, Pitshanger |
| 14 | Hackney | 31 | High - dense in De Beauvoir, Stoke Newington |
| 15 | Bexley | 31 | Moderate - scattered across borough |
Source: planning.data.gov.uk • Data as of March 2026
What does coverage mean in practice?
In Westminster and Kensington & Chelsea, conservation areas cover an estimated 75-80% of the borough area. This means the vast majority of homeowners need full planning permission for any visible external alteration. In Richmond, despite having the most conservation areas by count, coverage is somewhat lower because many designations cover smaller village centres and riverside areas. Boroughs like Barking & Dagenham (4 conservation areas) and Newham (7) have almost no heritage constraints - most extensions sail through under permitted development.
How Constraints Affect Your Extension
Not all constraints are equal. Some make extensions harder; others make them impossible. Here's a practical guide to what each constraint means for a typical home extension project.
High impact - changes the entire approach
- CAConservation area: Removes most PD rights. Need full planning permission. Materials must match or complement existing. Design scrutiny is detailed. Add 8-12 weeks to timeline and £2,000-5,000 to fees.
- LBListed building: Requires separate listed building consent for any alteration. Internal changes need consent too. Heritage statements, detailed drawings, and specialist materials required. Add £5,000-15,000 to fees and 12-20 weeks to timeline.
- A4Article 4 direction: Removes specific PD rights. Impact depends entirely on what the direction covers - could remove just HMO rights or could remove all extension rights. Must read the specific direction to know.
Medium impact - additional requirements
- TPOTree preservation orders: Cannot remove or significantly prune protected trees. Arboricultural assessment needed (£500-1,500). Foundation design may need modification. Can reduce buildable area.
- FRZFlood risk zones: Flood risk assessment required. May need raised floor levels, flood-resilient materials, or SuDS. Add £2,000-5,000 to costs. Zones 3a/3b may prevent ground-floor extensions entirely.
- GBGreen belt: Extensions must not be disproportionate to the original building. Typically limited to 30-50% increase in footprint. Two-storey extensions or large single-storey projects may be refused.
- AONBAONB / National park: PD rights reduced (no highway-facing dormers, single-storey side extensions only). Materials must respect landscape character. Design expected to be sympathetic.
Lower impact - rarely affects standard extensions
- SSSISSSI / SAC / Ramsar: Rarely affects residential extensions directly. May require ecological assessment if within buffer zone. Drainage to protected catchments can trigger Habitats Regulations Assessment.
- AWAncient woodland: 15m buffer zone applies. Very rare for residential properties to be within this buffer, but if they are, development is effectively refused.
- HCHeritage coast: Material consideration, not a statutory constraint. Impact on standard residential extensions is minimal unless the property is prominent in the landscape.
London Borough Constraint Detail
London is the most constrained region in England for residential extensions. Here are the boroughs with the most complete data on the national platform.
| Borough | Conservation areas | Listed buildings | Article 4 areas | TPO zones |
|---|---|---|---|---|
| Westminster | 56 | 3,455 | 10 | 263 |
| Kensington & Chelsea | 41 | 2,609 | 84 | 41 |
| Camden | 40 | 1,967 | 19 | - |
| Lambeth | 65 | 949 | 219 | 226 |
| Southwark | 56 | 909 | 480 | 724 |
| Tower Hamlets | 61 | 904 | 63 | - |
| Barnet | 16 | 649 | 48 | 3,217 |
| City of London | 28 | 636 | - | - |
| Brent | 23 | 582 | 158 | 301 |
| Waltham Forest | 15 | 161 | 807 | 217 |
Source: planning.data.gov.uk (Open Government Licence) • Data as of March 2026
Boroughs not shown maintain some or all constraint data locally rather than publishing to the national platform. This doesn't mean they have fewer constraints - Richmond, for example, has 87 conservation areas but limited data on other constraint types in the national dataset.
Notable patterns
- 1.Waltham Forest's Article 4 anomaly. 807 Article 4 direction areas is more than any other London borough - by a factor of 1.7x over the next highest (Southwark with 480). Many of these target HMO conversions and front garden parking rather than extensions, but homeowners should check the specific direction affecting their property.
- 2.Barnet's TPO density. 3,217 TPO zones is extraordinary - more than the rest of the top 10 boroughs combined. Barnet's suburban character with mature gardens and tree-lined streets means almost any extension requires an arboricultural assessment.
- 3.Southwark's constraint density. With 56 conservation areas, 909 listed buildings, 480 Article 4 areas, and 724 TPO zones, Southwark is arguably the most comprehensively constrained borough. Unlike Westminster or Kensington, this often catches homeowners off guard.
- 4.Westminster's listed building dominance. 3,455 listed buildings in one borough. Nearly every street in central Westminster contains listed structures. Even properties that aren't listed themselves are often in the setting of listed buildings, which is a material planning consideration.
Checking Your Property
You can check constraints yourself using planning.data.gov.uk's map viewer, but it requires knowing which datasets to search and how to interpret the results. Each constraint type is a separate dataset with its own query interface.
Alternatively, our free AI chat checks your exact address against all 17 constraint datasets simultaneously and tells you whether you have permitted development rights, which constraints affect your property, and what that means for your extension project. It takes under 60 seconds.
What to check before hiring an architect
- 1.Conservation area status - determines whether you need planning permission
- 2.Article 4 directions - may remove specific PD rights even outside conservation areas
- 3.Listed building status - affects the entire building, not just the facade
- 4.TPO zones - nearby trees can constrain foundation design and buildable area
- 5.Flood risk - may require flood risk assessment and specific construction methods
- 6.Green belt - limits the scale of extensions (disproportionate additions test)
Frequently Asked Questions
What is a planning constraint?
A planning constraint is any designation that restricts or modifies what you can do with your property. The main types are conservation areas (remove PD rights), listed buildings (require listed building consent), Article 4 directions (remove specific PD rights), tree preservation orders (protect trees from removal), flood risk zones (require flood risk assessments), and green belt (limit extension size). England has 17 types of constraint published to the national platform.
Which London borough has the most planning constraints?
Westminster has the most listed buildings (3,455) and is one of the most constrained overall. Waltham Forest has the most Article 4 direction areas (807). Richmond has the most conservation areas (87). Barnet has the most TPO zones (3,217). Southwark is arguably the most comprehensively constrained with high numbers across all four categories (56 CA, 909 listed, 480 Art4, 724 TPO).
Do conservation areas remove all permitted development rights?
Not all, but most relevant ones for extensions. In a conservation area, you cannot add a dormer window facing a highway, use cladding, add a chimney, or build certain outbuildings under PD. The Prior Approval route for larger extensions (up to 6m terraced/semi or 8m detached) is not available in conservation areas, but standard PD rear extensions (3m attached or 4m detached) are still permitted. Side extensions need planning permission. Most homeowners in conservation areas will need planning permission for any meaningful extension.
How do I check if my property has planning constraints?
Three options: (1) Use our free AI chat which checks all 17 datasets instantly for your exact address. (2) Search planning.data.gov.uk manually - each constraint type is a separate dataset. (3) Contact your local planning authority, who can provide a planning history and constraint search (sometimes for a fee). Option 1 is fastest and covers the most ground.
What is an Article 4 direction?
An Article 4 direction is a local order made by the council that removes specific permitted development rights in a defined area. They can target anything from extensions to satellite dishes to HMO conversions. The key issue is that you can't know what rights are removed without reading the specific direction - there are hundreds of different Article 4 directions in force across England, each with different terms.
Does being near a listed building affect my property?
Yes. Even if your property isn't listed, being within the "setting" of a listed building is a material planning consideration. If your extension could affect the character or appearance of the listed building when viewed from publicly accessible land, the planning authority can refuse permission or impose conditions on materials and design. The closer you are, the more scrutiny you'll face.
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