The short answer is: it depends on what you’re building and where your property sits. Many home improvements and extensions fall under permitted development rights, which means the work already has planning permission built in — you don’t need to apply. But those rights can be taken away depending on your location, and even when they apply, building regulations are a separate requirement you’ll almost certainly still need to meet.
Key takeaways
- Permitted development rights allow certain works without a planning application — but they don’t apply everywhere
- Conservation areas, listed buildings, and Article 4 directions all restrict what you can do without permission
- Cornwall has 145 conservation areas, so checking your property’s status before starting work matters
- Planning permission and building regulations are separate — you often need both
- The first step is understanding your property’s designation, not guessing
What are permitted development rights?
Permitted development rights are set out in the Town and Country Planning (General Permitted Development) (England) Order 2015. They give homeowners automatic planning permission for a defined range of works — things like rear extensions up to a certain size, loft conversions, outbuildings, and some changes to roofs and windows.
The practical effect is that you can carry out those works without submitting a planning application to Cornwall Council. The permission is already granted by law, subject to limits on size, height, materials, and position on your plot.
Those limits matter. Exceed them — even slightly — and you’re no longer within permitted development, and you’ll need a full application.
When do permitted development rights not apply?
This is where many homeowners get caught out. Permitted development rights can be restricted or removed entirely in certain situations, and Cornwall has quite a few of them.
Conservation areas. Cornwall has 145 conservation areas covering 4,070 hectares. Works that would be permitted development elsewhere — cladding, replacement windows and doors, extensions above a certain size, outbuildings, solar panels — require planning permission in a conservation area. The restrictions exist because small changes, individually harmless, can gradually erode the character that makes an area worth protecting.
Listed buildings. If your property is listed, permitted development rights don’t apply at all. Any work that would affect the character of the building — inside or outside — requires listed building consent, which is a separate process from standard planning permission.
Article 4 directions. Cornwall Council can issue an Article 4 direction to remove permitted development rights in a specific area, even outside a conservation area. These are used where the council wants tighter control over how properties are altered — often to protect the design character of a street or estate. In Looe, for example, an Article 4(2) direction covers the historic core, meaning that replacing windows, altering a roof, erecting a porch, or even painting a façade all require planning permission. You can check whether an Article 4 direction affects your property using the Map Layers tool on Cornwall Council’s planning portal.
Coastal locations and AONBs. Properties in or near designated coastal areas and Areas of Outstanding Natural Beauty face additional restrictions on the size and type of works permitted without an application.
Conditions on a previous planning permission. Sometimes a past planning permission granted for your property included conditions that removed permitted development rights. These are easy to miss and worth checking before assuming the default position applies.
Planning permission and building regulations are not the same thing
This distinction trips up a lot of people, including some who’ve done building work before.
Planning permission is about whether a development is appropriate — its size, appearance, position, and impact on neighbours and the surrounding area. Building regulations are about how it’s built — structural stability, fire safety, insulation, drainage, ventilation, and so on.
They’re governed by separate legislation and handled by separate departments. Getting one doesn’t give you the other.
For most building work, you’ll need both. An extension might fall within permitted development and need no planning application — but it will still need building regulations approval to make sure it’s structurally sound and meets current energy efficiency standards. Internal alterations — rewiring, knocking through walls, fitting a new bathroom — often need building regs sign-off even though no planning application is required.
The only common exception is very minor work that falls entirely outside both regimes — but that covers less than most people assume.
What should I do before starting work?
The most sensible first step is to establish what designations apply to your property. That tells you which rules you’re working under before you’ve spent a penny on drawings or quotes.
For most properties in Cornwall, that means checking three things:
- Is it in a conservation area? Cornwall Council’s planning search shows conservation area boundaries.
- Is it listed? The Historic England register is publicly searchable.
- Is there an Article 4 direction in force? Use the Map Layers tool on Cornwall Council’s interactive map and take a dated screenshot as a record of your check — Cornwall Council recommends this because new directions can take time to appear on the system.
If any of those apply, speak to a builder or planning consultant before committing to a design. The rules don’t necessarily stop you from doing what you want — they just mean the route is different, and the design may need to reflect the character of the area.
If none of them apply, check the size and position limits for the type of work you’re doing. The Planning Portal’s Interactive House is a straightforward way to look up what’s permitted for common projects.
Can I get written confirmation that I don’t need planning permission?
Yes. If your project falls within permitted development and you want formal confirmation — useful if you’re planning to sell the property, or simply want certainty — you can apply to Cornwall Council for a Lawful Development Certificate. This is a legal document confirming the work is lawful. There’s a fee, but it’s lower than a full planning application, and it protects you if questions arise later.
If you’ve already carried out work without permission and you’re not sure whether it was lawful, a retrospective application or a Certificate of Lawful Use is the route to regularising it.
Frequently asked questions
Do I need planning permission for a single-storey rear extension in Cornwall?
Usually not, if your property isn’t listed, isn’t in a conservation area, and no Article 4 direction applies. Under permitted development, a single-storey rear extension can be up to 4 metres deep for a detached house, or 3 metres for any other type of house. It must not exceed 4 metres in height. If you want to go beyond those dimensions, you’ll need a planning application — or you can use the Householder Prior Approval process for extensions up to 8 metres (detached) or 6 metres (other), subject to neighbour notification.
Does permitted development apply to listed buildings?
No. Permitted development rights do not apply to listed buildings. Any works affecting a listed building — inside or outside — require listed building consent in addition to planning permission if applicable.
What is an Article 4 direction and how do I know if one applies to me?
An Article 4 direction is issued by Cornwall Council to remove permitted development rights in a specific area. It means works you could otherwise carry out without permission now need a planning application. You can check whether your property is affected using the Map Layers tool on Cornwall Council’s planning portal, under Environment & Planning > Article 4 Direction Orders. Take a dated screenshot as a record.
Do I always need building regulations even if I don’t need planning permission?
Almost always, yes. Building regulations approval is required for most structural work, including extensions, loft conversions, garage conversions, and alterations to walls, roofs, electrics, or plumbing — regardless of whether planning permission is needed. The two are separate requirements. Not having building regulations sign-off can cause problems when you come to sell the property.
What happens if I carry out work without the required permission?
Cornwall Council can issue an enforcement notice requiring you to undo the work. For listed buildings, carrying out unauthorised works is a criminal offence. If you’ve bought a property where previous owners did unpermitted work, you inherit that risk. Retrospective planning permission is possible in some cases, but it’s not guaranteed and it’s always easier to get permission before starting than to regularise work after the fact.