Class Q barn conversion rules: Everything you need to know 

Following updates to permitted development rights under Class Q, there have been some significant changes that specifically relate to converting agricultural buildings for residential use. In this guide, we share key insights into the latest updates, and what it means for your project.

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What is Class Q permitted development?

Class Q permitted development is a process that gives landowners the right to convert agricultural buildings into a dwelling without the need of ‘full’ planning permission. It differs from traditional planning permission as it immediately grants permission if your barn conversion project falls within a certain criteria.  

Class Q planning consent: Eligibility criteria for a barn conversion 

• The barn must have been used for agricultural purposes on, or before, 20th March 2013 
• A single agricultural unit can be converted into a maximum of five dwellings 
• The building’s structural integrity is such that converting the barn would not require significant rebuilding 
• The barn conversion design does not exceed height or floor space restrictions 

As Class Q permitted development rights were significantly updated in 2024, it’s important that you follow the new and revised criteria for your project build. Although the updates generally increase your chances of building under permitted development rights, some elements do not – for example, there has been a reduction in the maximum floor space of an individual dwelling from 465m² to 150m². 

If you think your barn conversion project will be affected by the updates in Class Q, speak to an experienced architect. This can ensure you are aware of key discrepancies, changes or criteria and can maximise your chances of your project going ahead.

What changed in Class Q in 2024? 

In 2024, the following amendments were made to the Town and Country Planning Act, which came into force on the 21st May 2024. The documentation contains some significant changes to eligibility criteria that work in favour of landowners, enabling more barn conversion projects to go ahead without needing to apply for planning permission. 

The key changes to eligibility criteria are:

• Buildings that are part of an agricultural unit that have not been used for agriculture can now be developed 
• The number of buildings that can be converted as part of the project has increased from five to ten 
• Single storey extension height restrictions have increased to 4m 
• The maximum project floorspace has increased to 1000m²
• Access to an existing public highway must be suitable and specified 
• Windows, doors, roofing, additional insulation and drainage can be both installed and replaced under class Q, with a protrusion allowance of 0.2m 
• Significant reduction in maximum floor space of a single dwelling, from 465m² to 150m²

How to overcome challenges of the Class Q approval process

• Conduct a pre-application assessment 
• Work with an architectural consultant 
• Ensure your design respects local planning policies 
• Prepare thoroughly for any potential objections and appeals 
• Clearly evidence how your project meets Class Q criteria  

Unsure of where to start? Get prepared for your project with BASE and read our barn conversion planning guidelines 

Why might a Class Q application be rejected? 

There are some instances where your barn conversion project will not meet Class Q planning criteria. If this happens you will need to apply for planning permission before your project can go ahead.

 Instances where this might happen include the following: 

• If the barn is not structurally sound, and therefore is not suitable for conversion 
• If the barn is located in an unsuitable location (for instance, within an AONB) 
• If the development would significantly impact the surrounding environment 
• If the development would significantly disrupt the surrounding community 
• If the development does not comply with Class Q criteria 
• If the barn conversion project would cause a negative impact to the landscape 
• If your barn conversion planning documents are not sufficiently detailed 

If you think your barn conversion project may be eligible for Class Q permitted development rights, consult with an architect. The team at BASE have over 20 years of experience in bringing our clients’ visions to life, and can help you prepare and plan your project for the best chance of success.