Planning permission for an extension in the High Weald

If you've owned property in the area for any length of time you'll know the designation as the High Weald AONB (Area of Outstanding Natural Beauty). The Levelling-up and Regeneration Act 2023 renamed all 46 English AONBs to National Landscapes, taking effect from late 2023. The High Weald is now formally the High Weald National Landscape (HWNL). The legal protections — strongest level of landscape protection in English planning law, equivalent to a National Park for development control purposes — are unchanged.

Practically: when you read older planning documents referring to the AONB, they're talking about the same area. The boundary is the same. The HWNL covers 1,461 km² across Kent, East Sussex, West Sussex and Surrey, and runs through every village we work in — Rolvenden, Tenterden, Cranbrook, Hawkhurst, Biddenden, Goudhurst, Sissinghurst, and all the parishes between.

Outside designated areas, the General Permitted Development Order (GPDO) lets homeowners build many extensions without planning permission — single-storey rears up to 4m for detached / 3m for attached, single-storey side extensions up to half the width of the house, certain loft conversions, garden buildings of various sizes.

Inside the HWNL (and inside conservation areas, which often overlap), most of these permitted-development rights are removed or restricted:

• Two-storey rear extensions: not permitted development. Always need full planning.
• Side extensions: not permitted development. Always need full planning.
• Roof additions (dormers, mansards, hip-to-gable): not permitted on principal elevations facing a highway.
• Cladding alterations: not permitted in conservation areas.
• Front elevation alterations: heavily restricted.
• Outbuildings: still permitted in many cases, but with tighter limits on height and footprint.

An Article 4 direction is a local planning authority's tool to remove specific permitted-development rights from a defined area. They exist precisely because the standard GPDO would otherwise allow incremental changes (new windows, render, satellite dishes, painted brickwork) that erode the character of a historic place.

Around our patch, Article 4 directions apply in:

• Tenterden — central High Street and adjoining lanes (Ashford Borough Council).
• Rolvenden — parts of the central village street (Ashford Borough Council).
• Cranbrook — historic core including Stone Street, High Street, Carriers Road (Tunbridge Wells Borough Council).
• Biddenden — the High Street conservation area (Ashford Borough Council).
• Smaller areas in Hawkhurst and Goudhurst.

Pre-application advice. Optional but recommended. You submit drawings + a brief covering letter to the local planning authority; an officer reviews and writes back with a preliminary view. Fees: Ashford BC £162 for householder pre-app (2026), Tunbridge Wells BC £150-£300 depending on scale, Folkestone & Hythe DC £155. The officer's response is non-binding but in practice strongly predicts the outcome of a full application.

Full householder planning application. Submitted via the Planning Portal. Fee for 2026: £258 for a householder application in England. You'll need scaled existing and proposed drawings (plans, elevations, section, site plan, location plan), a design and access statement (for sites in a conservation area or HWNL), and potentially a heritage statement for listed buildings.

Validation. The LPA checks your application is complete. This usually takes 5-15 working days; if anything is missing, the clock doesn't start until you've supplied it.

Determination period. Statutory 8 weeks for householder applications. In practice, more contentious applications in the HWNL often run to 10-13 weeks. Either a planning officer makes the decision under delegated powers (most householder applications) or it goes to a planning committee for elected councillors to decide.

Conditions discharge. Approval usually comes with conditions — materials samples, drainage details, biodiversity gain plan, hours of working. These need formal discharge before or during construction, each with its own fee.

Officers in the HWNL apply the High Weald National Landscape Management Plan 2024-2029 as a material consideration. The plan sets out the qualities of place the designation exists to protect — the medieval pattern of small fields and shaws, the ridge-top settlements, the timber-framed and weatherboarded vernacular, the steeply pitched peg-tile roofs.

What that means in practice for extension design:

• Subordinate massing. Extensions should read as additions, not as competing volumes. Lower ridge lines, set-back footprints, and clear hierarchy between original and new.
• Traditional roof pitches (40-50°) on extensions visible from public viewpoints. Flat roofs are sometimes accepted on contemporary additions where the architect makes the case.
• Materials that match the host building: weatherboarding (painted black, off-white, or natural-aged), brickwork in lime mortar, peg tile or plain clay tile roofs, painted softwood or aluminium-clad timber casements with slim sight lines.
• Avoid: UPVC windows, concrete interlocking roof tiles, render on previously unrendered brick, large unbroken glazed elevations that don't relate to the house's window rhythm.

For any extension on or close to a listed building, the application will need a heritage statement — a written assessment of the building's significance and how the proposal affects it. For Grade II* and Grade I, this becomes a full Heritage Impact Assessment, often written by a specialist heritage consultant.

The HIA is read carefully by the conservation officer. A well-argued HIA can unlock approvals for changes that a thin application would never have got past validation. We routinely engage with the heritage consultant early — at concept design stage — to align the proposed scheme with the building's significance from the start.

Pre-app advice: 4-8 weeks to receive the officer's written response.

Full householder application: 10-13 weeks from validation to decision in most HWNL cases.

Listed Building Consent (in parallel with planning if both required): another 8-13 weeks.

Conditions discharge: 2-8 weeks per condition.

Realistic total from first concept sketch to start on site: 6-12 months for a straightforward extension in the HWNL; 9-18 months for a listed building.