Conservation area rules

If your property is in a conservation area, the normal permitted development rules change. Some rights are removed entirely. Others shrink. A few stay the same. This guide walks through exactly what changes, with a focus on the most common UK homeowner projects: extensions, loft conversions, windows, and external alterations.

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What you lose in a conservation area

The General Permitted Development Order 2015 lists several permitted development rights that are removed inside a conservation area. The biggest ones:

✗Side extensions. Class A side extensions are removed entirelyin conservation areas. You can’t build a single storey side extension under permitted development — you’ll need a full planning application regardless of size.
✗Exterior cladding. Stone, artificial stone, pebble dash, render, timber, plastic or tiles on the exterior of a house is removed. You need permission to clad or re-clad in a conservation area.
✗Two storey rear extensions. Class A two-storey rear extensions (3m deep, 7m from boundary) are removed. Single storey rear extensions are still allowed but with tighter limits.
✗Class B loft conversions with dormers. You can still convert a loft internally, but adding a roof-slope dormer under permitted development is removed. A dormer in a conservation area needs full planning permission.
✗Roof alterations. Class C rights to alter the roof shape are removed for principal elevations that face a highway.
✗Outbuildings at the side. Class E outbuildings can’t be built between the side elevation of the house and the side boundary.

What you keep in a conservation area

Conservation area designation doesn’t remove all permitted development rights. You still have meaningful flexibility.

✓Single storey rear extensions. Up to 3m deep on all house types (not 4m on detached as on unrestricted land). Max 4m height, 3m eaves. Materials must match the existing house.
✓Porches. Under 3 m² floor area, 3m high, 2m from the highway. Class D applies in conservation areas.
✓Outbuildings behind the house. Garden rooms, home offices, and summer houses are still permitted development under Class E, subject to the usual size, height, and 50% curtilage coverage limits.
✓Solar panels on non-highway-facing slopes. Part 14 still applies. Panels on a rear or side roof slope (not facing a highway) are permitted.
✓Fences, walls, and gates. Under 2m high (1m adjacent to a highway). Class A of Part 2 still applies.
✓Internal alterations. Most internal changes don’t need planning permission at all. Conservation area status doesn’t restrict what you do inside your house (unless the property is also listed, in which case listed building consent is needed for many internal changes).

When you do apply, how strict will the council be?

Any planning application in a conservation area is assessed against the character appraisal for that specific conservation area. The council will be looking for:

• Materials that match or complement the existing building. Brick bonds, pointing, window frames, roof tiles, ironwork — all matter.
• Scale and proportion consistent with neighbours. Oversized extensions that dominate the streetscape are the most common refusal reason.
• Minimal impact on the setting. Views from the street, sightlines through the area, and the character of shared boundaries.
• Traditional detailing where appropriate. Sash windows, original door styles, chimney pots, and cast iron details are often required to stay.

The most successful applications in conservation areas are designed by an architect or designer familiar with conservation area guidance. Pre-application advice from the council is strongly recommended for any substantial alteration.

Article 4 Directions — the extra layer

On top of the base conservation area rules, your street might also have an Article 4 Direction. Councils issue these in particularly sensitive conservation areas to remove additional permitted development rights. Common targets:

• Window replacements (especially switching materials)
• Front door replacements
• External painting of brickwork
• Paving over front gardens / dropped kerbs
• Roof material changes
• Satellite dishes on certain elevations

Article 4 Directions are highly localised — your neighbour two streets over might not be affected. Our free check queries the live Article 4 boundary data for your postcode, so you’ll know immediately which rights (if any) are removed at your specific address. For the full technical guide, read our Article 4 Directions explained page.

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Planning an extension in a conservation area?

Our £9 Full Report pulls in recent approvals and refusals in your conservation area from real council decisions. You see which designs got through, which didn’t, what the top refusal reasons were, and the specific constraints on your address. Delivered as a PDF.

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Frequently asked questions

What is a conservation area?

A conservation area is an area designated by a local planning authority as having special architectural or historic interest, the character or appearance of which it is desirable to preserve or enhance. There are over 10,000 conservation areas in England. Each one is defined by a boundary map published by the council and comes with a character appraisal describing what makes it special and what kinds of change are appropriate.

Am I in a conservation area?

You can check with your council’s planning portal, or use our free postcode checker which queries the live conservation area boundaries from planning.data.gov.uk. Enter your postcode and we’ll tell you instantly which conservation area (if any) your property sits within.

What can I build in a conservation area?

You can still do most things — rear extensions within tighter limits, loft conversions (sometimes), garden rooms, porches, solar panels on non-highway-facing slopes, fences, roof repairs. What you generally can’t do without planning permission: side extensions, cladding, adding a dormer to a roof slope facing the highway, or anything that projects in front of the principal elevation. The exact rules depend on which permitted development class applies to your project.

Do I need planning permission for a rear extension in a conservation area?

Single storey rear extensions up to 3m deep (for all house types, not just terraced) are usually still permitted development in a conservation area. Anything deeper, or any two-storey rear extension, needs planning permission. Materials must match the existing house, and the design will be scrutinised more closely if you do need to apply. An Article 4 Direction on your street may remove the right entirely.

Can I replace my windows in a conservation area?

Like-for-like replacements in the same material and style are usually fine. Switching from timber to UPVC, changing the pane divisions, or altering the proportions will often need planning permission in a conservation area — especially if an Article 4 Direction is in force. Check your property on our free postcode checker or ask the council before ordering windows.

What is an Article 4 Direction and how does it affect me?

An Article 4 Direction is an extra layer of restriction a council can put on top of a conservation area. It removes specific permitted development rights for a defined area — often a single street or cluster of streets. Common examples in London: removing the right to replace original windows, paint external brickwork, pave over front gardens, or replace front doors. If your property is covered by an Article 4 Direction, you’ll need planning permission for those specific changes even if they would normally be permitted development.