Everything you need to know about building an extension in an Area of Outstanding Natural Beauty
Founder, Planning to Build
If your property lies within an Area of Outstanding Natural Beauty (ANOB), you’ll need to take extra care when planning any kind of building work. These areas are protected for their exceptional landscape and scenic value and that means stricter planning rules apply.
In this guide, we’ll explain what AONB designation means, how it affects your chances of building or extending a home, and what you can do to give your project the best chance of approval.
What is an Area of Outstanding Natural Beauty?
Areas of Outstanding Natural Beauty (AONBs) are nationally protected landscapes, recognised for their distinctive character, natural beauty, and cultural value. There are 34 AONBs in England, 4 in Wales, and 9 in Northern Ireland, covering about 18% of the UK countryside.
The main purpose of AONB designation is to conserve and enhance the natural beauty of the landscape. But they also aim to support the economic and social wellbeing of local communities.
Planning policy in these areas places a strong emphasis on preserving character, protecting views, and limiting visual intrusion from new development.
Can you build in an AONB?
Yes - but your plans will be subject to stricter scrutiny than in non-designated areas.
Development is not banned altogether, but proposals must:
- Conserve and enhance the landscape
- Avoid harming the setting or scenic quality of the area
- Be sensitively designed and well-sited
Even modest extensions or outbuildings can be refused if they’re considered to detract from the character of the AONB. If you’re proposing a new house, replacement dwelling, or significant alteration, you’ll need to make a strong case and demonstrate how the design respects the local environment.
Do permitted development rights apply?
In many AONBs, permitted development rights are reduced or removed altogether, especially for things like:
- Rear extensions over a certain size.
- Side extensions.
- Roof enlargements (e.g. loft conversions or dormers)
- Outbuildings
- Cladding or external finishes
In these areas, you’ll usually need to apply for full planning permission, even for work that might not require it elsewhere.
Before starting, always check with your local planning authority or use an online planning tool to find out what rules apply to your property.
A practical example...
Tom and Sarah owned a farmhouse in the Chilterns AONB and wanted to build a garden room with floor-to-ceiling windows overlooking the valley.
Their initial plans were refused as the local authority felt the glass would create too much glare and harm the area’s rural character.
Working with a local architect, they revised the design to reduce glazing, lower the roof height, and use timber cladding that matched existing outbuildings. They also added native planting to soften the appearance. The new application was approved, and the garden room blends discreetly into the landscape.
Tips for homeowners looking to extend
If you're hoping to extend an existing home in an AONB, here are some key tips to help you navigate the planning process and give your project the best possible chance of success.
Start with a planning consultant
A planning consultant with experience in AONB applications can be an invaluable guide. These professionals understand the local development plans, design codes, and landscape character assessments that influence decision-making. They can help you avoid common mistakes, flag issues that could lead to refusal, and suggest adjustments to make your proposal more acceptable. In sensitive locations like AONBs, having the right consultant on board can make the difference between a smooth application and a costly refusal..
Design with the landscape in mind
The defining feature of an AONB is its scenery. So any development must respect and respond to that setting. Think about how your proposal will look from nearby footpaths, hillsides, and roads. Choose materials that reflect local building traditions, like stone, timber, or lime render. Keep rooflines and building footprints compact, and avoid designs that jar with the rural context. While a modern approach isn’t out of the question, it needs to be thoughtfully integrated, using muted colours, natural finishes, and simple forms that complement rather than compete with the landscape.
Keep it discreet
In an AONB, visual impact is everything. Buildings that dominate the skyline, break natural sightlines, or sit in open exposed locations are much more likely to be refused. Where possible, position new structures behind existing buildings, hedgerows, or woodland to reduce visibility. Consider lowering floor levels into the ground, using sedum or green roofs, and avoiding features like bright render or reflective glass that draw the eye. A well-designed building should feel like a natural part of the landscape, not a disruption to it.
Avoid light pollution
Preserving dark skies is a growing priority in many AONBs, particularly those with designated stargazing or wildlife areas. Glazing, especially when used extensively on elevations or roofs, can contribute to light spill, which affects not only the night-time view but also nocturnal wildlife. To avoid this, keep glazed areas modest and use internal blinds or low-impact lighting. Choose downward-facing, motion-sensor outdoor lights where needed, and avoid lighting pathways or driveways unnecessarily. A well-considered lighting strategy can show planners that you’re taking the local environment seriously.
Building in an Area of Outstanding Natural Beauty isn’t impossible, but it does require a sensitive approach. Local authorities will expect high-quality design and a clear effort to minimise the impact on the landscape.
If your home is in an AONB, it’s essential to understand the extra planning constraints and get advice early in the process. That way, you’ll be better placed to adapt your plans and avoid common pitfalls.