Permitted Development vs Planning Permission: What You Need to Know for Extensions & Conversions in South Downs National Park

When you’re considering extending or converting a building within the South Downs National Park (SDNP), it’s essential to understand the difference between Permitted Development (PD) rights and when full Planning Permission is required. This not only helps avoid delays or refusals but ensures that any work respects the special qualities of the National Park.

What is Permitted Development (PD)

• Definition: PD rights are rights written into law (the General Permitted Development Order etc.) that allow certain types of works without needing to apply for full planning permission.

• Limitations: PD does not mean “anything goes.” There are size, height, location, material, and impact constraints. PD rights can also be removed or limited by other designations or legal mechanisms.

Key Constraints in the South Downs National Park

Because the SDNP is a protected landscape, there are extra layers of consideration:

1. Article 2(3) / Article 2(4) Land

   • Much of the National Park is governed by Article 2(3) land under the GPDO. This doesn’t strip out all permissible PD rights, but tighter constraints often apply.

   • The presence of Article 4 Directions may further restrict PD rights (e.g. conservation of appearance in certain conservation areas).

     
     

2. Conservation Areas / Listed Buildings

   • If the building is listed, or in a conservation area, extra consent is almost always needed. Even small works (windows, doors, roofs) may require listed building consent.

   • The character, historic appearance, materials, and setting of the building are relevant in decisions.

     
     

3. Landscape & Scenic Character

   • Any development must conserve and, where possible, enhance the natural beauty, wildlife, and cultural heritage of the Park. Even PD works may be refused if they have harmful impacts.

     
     

4. Local Plan Policies

   • The SDNP’s adopted Local Plan (2014-2033) sets policies that apply to all development. Extensions and conversions need to comply with design, scale, materials, landscape, ecology, etc.

   • The Park Authority also has Technical Advice Notes (TANs) and supplementary guidance that affect what is acceptable.

     
     

5. Removed or Restricted PD Rights

   • Some properties have had PD rights removed via planning conditions or Article 4 Directions. Always check the planning history of the property.

     
     

When You’ll Need Planning Permission

You’ll need to make a full planning application if:

• The proposed works fall outside permitted development rights (too large, too high, poor materials, etc.).

• The building/site is listed, in a conservation area (or another sensitive designation), or subject to an Article 4.

• The works impact the National Park’s special qualities (visual impact, involvement with ecology, heritage, etc.).

• It involves conversion of agricultural or other non‐residential buildings, particularly for dwelling uses – changes of use are commonly subject to full planning control within SDNP.

• For larger extensions or when prior approval is required under certain PD classes and that process is triggered.

  
  

Prior Approval / Lawful Development Certificates

• Prior Approval: Some permitted development classes allow larger extensions but only if you apply for prior approval. This is a lighter process than full permission but still requires notification, neighbour consultation, and checks (on things like matching materials, flood risk, impact).

• Lawful Development Certificate: If you're unsure whether planning permission is needed, you can apply for a lawful development certificate. This is formal confirmation that your proposal is lawful / does not require permission. It is valuable in case of future enforcement or when selling.

Practical Do’s & Don’ts for Extensions & Conversions

To improve your chance of success:

• Always check whether your property is in the National Park, a conservation area, or is a listed building.

• Review previous permissions & planning history. Any conditions restricting PD?

• Before designing, consult the SDNP Local Plan and any TANs (Technical Advice).

• Use materials sympathetic to the local vernacular.

• Engage early, possibly via a pre-application discussion with SDNPA.

• If you are planning large or sensitive work, design for the landscape and setting (minimise visual intrusion, respect local character).

• If in doubt, get specialist advice (architect, planning consultant).

  
  

Examples / What PD Might Allow vs What You Probably Need Permission For

Project	Might be Covered by PD (if all constraints satisfied)	Likely Need Planning Permission
Small single-storey rear extension / modest side extension (within size and height limits)	Yes, possibly, under Class A PD, if materials and scale acceptable and it's not in a highly sensitive setting.	If extension is large, visible from public view, uses non-traditional materials, or in conservation area/listed building.
Loft conversion with dormer	Possibly under PD (roof additions), if on rear, volume limits, materials match etc.	If dormer front-facing, alters roofline noticeably, impacts neighbours, significant structural alteration.
Converting an agricultural barn to a dwelling (change of use)	Unlikely under PD in SDNP; change of use PD rights (like Class Q) are mostly excluded in Protected Landscapes.	Full planning application with supporting documents (design, impact, ecology etc.).
Outbuildings / garden structures	Small garden buildings under certain height / distance may be PD.	Anything large, visible, close to boundaries, or in heritage/conservation contexts.

Why These Rules Matter in the SDNP

Because SDNP is a protected landscape with legal statutory purposes (conserving & enhancing natural beauty, wildlife etc.), there is extra weight given in decision-making to the landscape, ecology, heritage & local character. It’s not simply about ticking the size/volume boxes – the qualitative impacts matter.

Also, as of 2025, there have been government proposals and changes that relate to PD, but many exclude protected landscapes (National Parks) from more relaxed PD rights (for example change of use under Class Q) to preserve landscape protections.

Relevant Information / Links

If you want to share further reading or refer clients, here are some key SDNP / related resources:

• SDNP Permitted Development guidance: Permitted Development - South Downs National Park South Downs National Park Authority

• SDNP Technical Advice Notes (especially on Extensions & Replacement Dwellings) South Downs National Park Authority

• SDNP Local Plan (2014-2033) policies for design, landscape, heritage etc. Brighton & Hove City Council

• Planning Portal – guidance on permitted development generally. Planning Portal

• Lawful Development Certificates – when in doubt, get formal confirmation.