A large share of Oxfordshire’s most attractive housing sits in conservation areas. In Oxford alone they include Jericho, Walton Manor, the North Oxford Victorian Suburb, Headington Hill, Old Headington, Iffley and Wolvercote with Godstow, and market towns such as Chipping Norton have conservation areas covering most of their historic centres. Extending a house in one of these areas is entirely possible, but the rules are tighter than elsewhere and the design needs more thought. This guide explains what changes and how to approach a project.

What a conservation area means

A conservation area is an area of special architectural or historic interest whose character or appearance the council considers worth preserving or enhancing. When the council decides a planning application in one, it has a legal duty to pay special attention to that. Conservation areas are different from listed buildings: the protection applies to the area as a whole rather than to the individual building, although some houses in conservation areas are also listed. If yours is, listed building consent is needed as well.

Start by checking whether your property is in a conservation area using your council’s map (Oxford City, Cherwell or West Oxfordshire), then read the conservation area appraisal. It describes what the council sees as the area’s character and is a useful brief for your designer.

What you can still do under permitted development

Houses in conservation areas keep some permitted development rights. A single-storey rear extension can usually be built without planning permission if it:

  • extends no more than 3 metres beyond the original rear wall of a semi-detached or terraced house, or 4 metres for a detached house
  • is no more than 4 metres high, with eaves no higher than 3 metres if it is within 2 metres of a boundary
  • uses materials similar in appearance to the existing house
  • together with other extensions and outbuildings, covers no more than half the land around the original house

Other conditions apply, so check the full rules or apply for a Lawful Development Certificate if you want certainty before building.

What needs planning permission in a conservation area

Several things that are permitted development elsewhere need a planning application in a conservation area:

  • Side extensions of any size.
  • Rear extensions of more than one storey.
  • Cladding the outside of the house in stone, render, timber, tiles or similar materials.
  • Roof extensions such as dormers, which are not permitted development on houses in conservation areas.
  • Larger single-storey rear extensions of up to 6 or 8 metres under the prior approval scheme, which does not apply in conservation areas.

Article 4 directions

Some conservation areas go further. Article 4 directions remove specific permitted development rights. In Oxford, for example, the Jericho and Osney Town directions mean planning permission is needed to change windows and doors on street-facing elevations. Check whether a direction covers your street before assuming anything is permitted.

Designing an extension that gets approved

Councils look for extensions that preserve or enhance the character of the area. In practice that tends to mean:

  • Keeping to the rear, where the extension has less impact on the street scene.
  • Staying subordinate: lower than the main roof, set in from the sides, and smaller in scale than the original house.
  • Using appropriate materials: matching brick, natural stone, lime mortar, clay or slate roof tiles, or high-quality contemporary materials where a deliberately modern design is proposed.
  • Respecting gaps and views: in areas like North Oxford, the spaces between large villas and views of gardens are often part of the character.
  • Protecting features such as boundary walls, chimneys, original windows and mature trees.

Pre-application advice from the council is particularly valuable in conservation areas. It costs a modest fee but can save a refusal and resubmission.

Other consents to watch for

Trees

Trees in conservation areas are protected. You must give the council six weeks’ notice before cutting down or carrying out work on a tree with a trunk diameter of more than 75mm, measured 1.5 metres above the ground. This matters for extensions, where foundations and access can affect nearby trees.

Demolition

Demolishing an unlisted building with a volume of more than 115 cubic metres in a conservation area needs planning permission. Demolishing certain walls, gates and fences also needs permission, depending on their height and location.

Building Regulations and party walls

As with any extension, you will need Building Regulations approval, and if the work affects a shared wall or involves excavating close to a neighbour’s foundations, notice under the Party Wall etc. Act 1996.

A typical route

  • Check the conservation area, listing status and any Article 4 direction.
  • Commission a measured survey and initial design.
  • Seek pre-application advice from the council.
  • Submit a householder planning application with a heritage or design statement.
  • Most decisions are due within eight weeks of validation. Approval of materials is often a condition.
  • Obtain Building Regulations approval, serve party wall notices and plan the build.

How we can help

North Oxford Developments has been building house extensions in Oxford, Oxfordshire and the Cotswolds since 1984. We work alongside architects and planning consultants where needed and can help from the early site visit onwards, so the design you submit is practical to build. At Cox Lane in Chipping Norton we built a double storey extension in natural Cotswold stone that was integrated with the original period property. If you are thinking about extending in a conservation area, we would be glad to talk it through.