Agricultural barns can make impressive residential spaces. Their uninterrupted floor plans and high vaulted ceilings offer unique architectural possibilities for creating characterful living accommodation.

Barn conversions also have planning advantages. Unlike building a new dwelling in the countryside, existing structures reduce risks related to overdevelopment and aesthetics. Additionally, many agricultural sites benefit from permitted development (PD) rights – planning legislation that allows certain types of development without full planning permission.

In May 2024, revisions to Class Q of the General Permitted Development Order (GPDO) appeared to grant landowners even greater benefits for converting agricultural buildings into homes. However, a closer look reveals that many of the same checks and balances remain, making the process surprisingly similar to full planning permission for many applicants.

This guide summarises which sites qualify for PD rights, the latest Class Q rules, and how to apply for council approval. For sites without PD rights, I’ll explain the main criteria councils use to evaluate full planning applications and share tips to improve your chances of success.

I hope you find this guide helpful. If you have questions about your specific project, please feel free to get in touch.

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Sandy Rendel Architects converted a Dutch barn in West Sussex into a house clad in corrugated steel. Photo by Jim Stephenson.

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Which Barn Conversion Sites have Permitted Development Rights?

The Town and Country Planning (General Permitted Development etc.) (England) (Amendment) Order 2024, which amends Class Q of Part 3, considers the change of use of agricultural units to residential use.

‘Agricultural units’ being land, dwellings, and other buildings used for farming.

The rights do not apply to:

• Sites on article 2(3) land, including national parks and areas of outstanding natural beauty (AONB).
• Listed buildings.
• Scheduled monuments.
• Sites of Special Scientific Interest (SSSI).

Permitted development legislation for residential barn conversions in Wales is similar to that in England. However, there is no direct equivalent in Scotland or Northern Ireland.

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This Grade-2 listed barn is to be converted into a private home by Clementine Blakemore Architects.

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Class Q Permitted Development Rules

The updated Class Q, effective from 21 May 2024, is designed to support the reuse of existing agricultural structures, including barns, stables, and other farm buildings. A set of criteria must be followed to gain approval.

The new criteria focus on the site's history rather than its specific use, which was the case under previous legislation.

The main requirements are as follows:

Land Use

• The building must have been in agricultural use on or before 24 July 2023. If brought into agricultural use after this date, 10 years must pass before conversion.
• The land must have suitable existing access to a public highway.

Number and Size of Dwellings

• A maximum of 10 dwellings is permitted (previously 5).
• Maximum total floorspace: 1,000 square metres (up from 865 square metres).
• Each new dwelling is limited to 150 square metres (down from 465 square metres).
• Dwellings must meet minimum spaces standards.

Extensions

• Single-storey extensions are now allowed at the rear (previously prohibited), provided hardstanding was in place on or before 24 July 2023, or at least 10 years prior if installed later.
• Extensions are limited to 4 metres from the existing rear wall.
• They must not extend beyond a side wall or principal elevation.
• Eaves must not exceed the existing height, and roofs must not exceed the highest part of the existing roof or 4 metres above ground.

Alterations

• New windows, doors, roofs, and exterior walls necessary for conversion to residential use.
• Installation of water, drainage, electricity, gas, and other services.
• Partial demolitions (wording regarding structural integrity from earlier rules have been removed).

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Barn conversion to house permitted development rules (view of a barn from the rear): 1) Conversions limited to 150 square metres; 2) Extensions must be sited on hardstanding that was in place on or before 24 July 2023, or at least 10 years prior if laid later; 3) Extensions are limited to 4 metres from the rear wall; 4) Extension eaves no higher than existing; 5) Extension roof no higher than existing; 6) Extension cannot be sited beyond the side wall or principle elevation; 7) External alterations to the existing building are permitted.

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Prior Approval for Barn Conversions

Although Class Q removes the need for full planning permission, you must still seek 'prior approval' from your local planning authority (LPA) before starting work.

Prior approval involves providing information for the LPA to assess:

• Traffic impacts of the dwelling(s).
• Noise levels.
• Contamination risks.
• Flood risks (if in a flood zone).
• Suitability of the site’s location.
• External appearance.
• Natural light provision in the dwelling(s).
• The impact of extensions on neighbouring properties.

As a result, applications can become complex – far from the streamlined system often portrayed.

Applications have a 56-day determination period, though timelines can vary based on case complexity.

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Class Q Transitional Provisions

The changes to Class Q significantly broaden the scope of permitted development, potentially enabling more barns and other agricultural buildings to be converted into homes. However, new restrictions on individual dwelling sizes and access requirements are notable.

To ease the transition, a transitional period until 20 May 2025 allows applications to be submitted under the old Class Q rules (prior to 21 May 2024), though these applications will not benefit from the new extension allowance.

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General Planning Criteria for Converting a Barn

If your site or project falls outside Class Q, you will need to apply for full planning permission.

LPAs will generally evaluate your plans against the following criteria:

Land Use

• Policies aim to protect agriculture and the rural economy. LPAs will assess the impact of converting the site from agricultural to residential use.

Design

• The proposals must preserve the architectural character of the existing building and its surrounding landscape. While some policies set parameters for size and shape, guidance is often subjective and requires careful interpretation.

Access

• The LPA will assess the suitability of existing or proposed access for vehicles and pedestrians. Residential access must be separate from farming activities to avoid disrupting operations.

Energy

• New homes must have a low carbon footprint to meet net zero obligations. Barn conversions must be highly thermally efficient and the LAP may request you incorporate low-carbon heating and sustainable drainage systems.

Biodiversity

• Protecting and enhancing wildlife habitats is often required. This typically involves habitat surveys and landscaping proposals from specialists.

In most cases, you will also need to address criteria similar to the Class Q prior approval requirements.

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Residential barn conversion in Norfolk by Lynch Architects. Photo by Maisie Hill.

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Tips for Gaining Planning Permission for a Barn Conversion

Converting a barn under full planning permission can be complex, especially if the site is listed or within a designated area such as an Area of Outstanding Natural Beauty (AONB).

Here are some tips to improve your chances of success:

1. Understand planning policies early: Familiarise yourself with relevant policies before beginning design work to save time and effort.
2. Research similar projects: A planning search of comparable local projects can help you understand what has been approved and why.
3. Seek pre-application advice: This provides valuable feedback on your proposals and helps build rapport with the LPA. The case officer handling your pre-application is often assigned to the full application.
4. Appoint experienced professionals: A skilled residential architect can design a high-quality scheme, coordinate work with consultants, and manage the planning process on your behalf, saving you time and stress.

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Planning Conditions & Obligations

Securing planning approval is obviously a key milestone but there are important considerations and potential obligations to address after approval.

Community Infrastructure Levy (CIL)

Some local authorities apply  Community Infrastructure Levy (CIL) to barn conversions (Class Q or full planning). Homeowners are exempt if the property is their principal residence for 3 or more years post completion. Note than you must apply for relief before starting work to avoid charges.

Full Planning Permission Requirements

You may need to discharge planning conditions before construction. Conditions require clarification of specific aspects of the scheme. Separate applications are needed, typically taking several weeks.

Section 106 Agreements (England/Wales) or Section 75 (Scotland) seek financial contributions for local infrastructure improvements.

Finally, be aware of affordable housing contributions. These are mainly applied in London (where there aren’t many barn conversion opportunities), but some councils outside the capital are adopting this policy—notably Elmbridge Borough Council in Surrey and Three Rivers District Council in Hertfordshire.

Check your local authority's planning website for applicability.

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Barn conversion interior by TYPE. Photo by Rory Gardiner.

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Barn Conversions: Permitted Development vs Full Planning

In summary, Class Q offers the most straightforward route for converting a barn into residential use. Design parameters are clearly defined and planning contributions, with the exception of the CIL, do not apply.

However, as with earlier guidance, the requirement for prior approval on a range of design and technical matters undermines the streamlined intent of permitted development. In practice, the process often resembles full planning permission.

The new floor area restrictions (maximum of 150 square metres per dwelling) are also likely to bring many larger barn conversion projects into the scope of full planning.

Whichever route you choose, enlisting the services of a skilled residential architect will significantly enhance your chances of success.

Best of luck with your barn conversion project!

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The information provided in this article is intended for general guidance and educational purposes only. For specific expert advice on your project, consult a skilled residential architect featured on Designs in Detail.

About the Author

I am an architect with over twenty years of experience, working on projects that include historic building restorations, such as barn conversions, as well as contemporary extensions and new-build homes across London and the UK.

In addition to my architectural practice, I also work as a content creator, providing homeowners with information to assist them with their building projects and promoting the architecture profession.

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