If your property is in a conservation area, the planning rules for extensions, outbuildings, and alterations are significantly more restrictive than for ordinary residential properties. Conservation areas cover much of historic urban Britain — entire streets of Victorian and Georgian terraces, town centres, and rural villages — and protecting their character is a planning priority. This guide explains what you can and can’t build in a conservation area.

What Is a Conservation Area?

A conservation area is an area designated by the local planning authority as having special architectural or historic interest. The character and appearance of the area is worth preserving or enhancing. There are approximately 10,000 conservation areas in England.

Conservation area designation affects planning applications and permitted development rights — but it does not restrict internal works or changes that don’t affect the external appearance of the building.

How Conservation Areas Restrict Permitted Development Rights

In a conservation area, the following permitted development rights are removed or restricted:

Extensions (Class A)

In a conservation area, the standard Class A permitted development rights for extensions apply EXCEPT:

• Side extensions visible from a public highway require planning permission in a conservation area — the permitted development right for side extensions is removed
• The prior approval scheme for larger home extensions (6m/8m) does not apply in conservation areas
• Cladding the exterior of the dwelling with stone, artificial stone, pebble dash, render, timber, plastic, or tiles requires planning permission

Rear extensions that are not visible from a road or public right of way can still be permitted development if they meet all the standard Class A conditions.

Outbuildings (Class E)

In a conservation area, outbuildings are more restricted. Any outbuilding to the side of the house (which would be visible from a road) requires planning permission. Outbuildings to the rear may still be permitted development if they meet size and location conditions.

Roof Alterations (Class C and B)

Adding a dormer window to a conservation area property almost always requires planning permission. Roof alterations that affect the appearance of the building from a public road, or that alter the shape of the roof, require permission in conservation areas.

Demolition (Article 81)

Demolishing a building in a conservation area requires Conservation Area Consent (now handled under planning permission for demolition). You cannot demolish structures without approval, even if they don’t appear particularly historic.

Trees

Trees in conservation areas that are not subject to a Tree Preservation Order (TPO) still have a 6-week notice requirement before any felling or significant pruning. You must notify the local authority, who can make a TPO within the 6 weeks to prevent the works.

What Can I Still Build Under Permitted Development in a Conservation Area?

Despite the restrictions, much is still possible:

• Rear extensions (single-storey, within standard PD limits) that are not visible from any highway or public right of way
• Internal works of any kind (no planning permission required for internal alterations)
• Like-for-like window and door replacements in similar materials (matching the existing style and material)
• Rear outbuildings meeting Class E conditions
• Rooflights on a rear roof slope not visible from a road

Getting Planning Permission in a Conservation Area

When planning permission is required for work in a conservation area, the proposal is assessed against:

• The conservation area’s character appraisal (most conservation areas have one — check the LPA’s website)
• National Planning Policy Framework (NPPF) policies on the historic environment (section 16)
• Local policies on design and heritage
• Any supplementary planning guidance on extensions in the conservation area

Key design principles that planning authorities look for in conservation area applications:

• Subservience: Extensions should be clearly subordinate to the main house — smaller in scale and visual weight
• Materials: Matching brick colour and bond, lime mortar rather than cement, timber joinery rather than PVC
• Setback: Setting the extension back from the original front wall, so the original building reads as primary
• Roof form: Often expected to match the existing roof pitch and style, or be clearly differentiated as contemporary (flat roof on a rear addition)
• Reversibility: Some authorities prefer additions that could theoretically be removed without harming the original building

Using an Architect in a Conservation Area

Working in a conservation area requires architectural skill that goes beyond technical drawing. A good architect will:

• Know the character appraisal and the LPA’s specific preferences for the area
• Have experience with conservation area applications in your local authority
• Know how to use contemporary design sympathetically rather than producing a pastiche
• Manage pre-application discussions with the conservation officer

A conservation officer’s support at pre-application stage is extremely valuable. Their informal endorsement of a scheme significantly increases approval chances.

Listed Buildings vs Conservation Areas

Being in a conservation area is different from being a listed building — these are separate designations:

• Conservation area: The area has special character; individual buildings have reduced permitted development rights but are not individually protected (unless also listed)
• Listed building: The individual building is protected. Any works to a listed building’s exterior or interior that would affect its character require Listed Building Consent — this is in addition to any planning permission required

A listed building in a conservation area needs both listed building consent and planning permission for most external works.

Frequently Asked Questions

Can I extend my house in a conservation area?

Yes — but permitted development rights are more restricted, and many extensions that would be permitted development elsewhere require planning permission. Rear extensions that are not visible from a road may still be permitted development. Check with your local authority or architect before proceeding.

Do I need special materials in a conservation area?

Often yes — planning authorities typically require materials that match or complement the existing building. This usually means matching brick, lime mortar, and timber joinery. Some authorities allow contemporary materials on clearly differentiated modern extensions.

Can I replace windows in a conservation area?

Like-for-like replacement in the same material and style is usually permitted development. Replacing timber sash windows with PVC requires planning permission in most conservation areas — and is often refused. Timber double-glazed units matching the original style are the standard compliant approach.

How do I find out if my property is in a conservation area?

Check your local planning authority’s website — most have a map of conservation areas. You can also ask for a formal confirmation from the LPA. The Planning Portal’s property search tool can also indicate this.

Is it harder to get planning permission in a conservation area?

Not necessarily harder, but different. The assessment criteria focus on character and appearance. A well-designed extension that respects the area’s character has very good approval prospects. Poorly designed extensions that clash with the character of the area will be refused.

Can Crown Architecture help with conservation area applications?

Yes — Crown Architecture has extensive experience with planning applications in conservation areas across London and the Home Counties. Call us on 07443 804841 to discuss your project.