Class Q barn conversions: what you need to know

Traditional barn conversions have always been popular. Turning an existing agricultural building into somewhere to live is an idea many landowners would love to do. A recent change in the law with the introduction of Class Q planning has simplified the rules on barn conversion. It’s clarified what you can convert, how many homes you can create and how much floor space you can add.

In this article, find out about Class Q and what you’re now allowed to do. Then discover how to submit your prior approval application so that it has the best chance of success.

What is Class Q planning?

You can now convert agricultural buildings to homes in England without full planning permission. The new rules come from the Town and Country Planning (General Permitted Development) (England) Order 2015. These Class Q permitted development rights apply across rural areas and some urban sites.

Class Q applies to buildings that were part of an established agricultural unit on 24th July 2023. If a site becomes part of an established agricultural unit after this date, you need to wait for 10 years from its construction.

The 2024 update makes barn conversions easier and faster. For example, you can now create up to 10 homes per agricultural unit instead of five.

You don’t have to go through the lengthy planning application process anymore. But, you must let your council run a few checks before they grant it prior approval. They include compliance with Class Q criteria like:

Compliance with legal provisions (like caps on dwelling numbers and types of land used)
Compliance with local planning regulations
Proving the building’s agricultural use on the relevant qualifying date

Although the planning process is now simpler, it’s a good idea to work with an architect. They can confirm your project’s eligibility and help you prepare a strong application.

WindsorPatania note: An established agricultural unit is agricultural land and buildings farmed together as one holding for agriculture. It either met the 24 July 2023 qualifying date or has been in such use for at least ten years before development begins

What changed in 2024

In force from 21 May 2024, SI 2024/579 from the Town and Country Planning Act:

Doubled the number of homes you can create under Class Q from five to 10
Increased the overall residential floor space permitted from 465 to 1,000m2 in each established agricultural unit
Permits the addition of a single-storey rear extension up to 4 metres deep (as long as it remains in the 1,000m2)

The 2024 changes also removed the “solely agricultural use” requirement. The law now extends to:

Unused agricultural buildings
Former agricultural buildings that are no longer in use for farming, as long as there’s been no agricultural activity since

Your conversion must meet the criteria within the Nationally Described Space Standard. Each building permitted under the new regulation must also have suitable existing access to a public highway.

WindsorPatania link: UK Outbuilding Planning Rules: Size Limits and Permitted Development Explained

How prior approval works

Contact the local planning authority to find out if you need prior approval.

The authority has 56 days to decide (30 April 2015) from receiving your application. If they do not respond within 56 days, you can proceed with the development.

Getting in touch with the council is a good idea, anyway. They’ll tell you what they expect and you get a chance to address any concerns. This increases the chances of approval for your development project.

Prior approval is light-touch compared to a full planning application. The local authority can only judge your application on the matters in the legislation. They cannot apply general planning policy or refuse your project on grounds outside those matters. So, for example, they can’t say “no” because the site is not allocated for housing in the Local Plan or the council dislikes the principle of new homes there in general policy terms.

To give yourself the best chance, develop a thorough understanding of what local planning authorities look for.

What Class Q covers

Class Q allows the residential conversion of agricultural buildings, like barns, grain stores and milking parlours into homes. This is under permitted development rights. Permitted development rights are projects for specific types of work that don’t need planning permission but do need prior planning approval.

Class Q of Part 3 (21 May 2024) of Schedule 2 covers three types of development:

Q(a): Change of use with no building works
Q(a)+Q(c): Change of use with building works
Q(a)+Q(b)+Q(c): Change of use with building works with rear extension

It’s important to know which works:

Are general development work under permitted development rights
Need planning permission

The rules only allow certain internal changes and building operations without planning permission. We’ll cover those now.

WindsorPatania link: Planning permission objections from neighbours: how to handle them

Change of use to homes

You convert the agricultural barn and any land within its curtilage to Class C3 dwellinghouses. This is a residential dwelling occupied by a single household in Use Class C3.

Curtilage is the land immediately around the building that is closely associated with it and serves it as part of the site. For example, the area used for access, parking, a small garden or domestic storage. This is typically what would be expected around a normal home.

The definition of curtilage for Class Q is quite modest. Think of it as the land the barn occupies or the minimum land next to it. It doesn’t include fields, paddocks or wider open farmland beyond a small domestic area.

You can create more than one dwelling from multiple agricultural buildings. That’s within a single agricultural unit. A single agricultural unit, in Class Q terms, is all the agricultural land and buildings that are farmed together under one occupation.

Each dwelling created must be a self-contained home. It can’t be a house in multiple occupation (HMO) or a short-term serviced let, for example.

Class Q(a)+Q(c)

Class Q is not a right to rebuild an agricultural building. The permitted development right assumes the existing structure can operate as a dwelling. You’ll need to order a structural survey to show the building is suitable for conversion.

Examples of when the condition of your barn might fail under Class Q rights are:

The frame is too weak and would need wholesale replacement.
The external walls would need rebuilding beyond what is reasonably necessary for a conversion.
The roof is largely missing so the works amount to a rebuild rather than a conversion.

If you want to carry out building operations as part of the conversion process, apply for Class Q(a)+Q(c). This will allow you to install or replace windows, doors, roofs and exterior walls. It also permits you to connect to services like water, drainage, electricity and gas. You can carry out partial demolition to the extent reasonably necessary for the works to take place.

You can undertake internal structural works under Class Q(a)+Q(c). They include adding internal walls and mezzanine or upper floors. Each habitable room has to meet the standards for natural light, size and suitability for living or sleeping purposes.

Class Q(a)+Q(b)+Q(c)

You may add a single-storey rear extension to the existing building. The extension must:

Be sited only to the rear
Extend no more than 4 metres beyond the rear wall
Have eaves no higher than the existing building’s eaves

WindsorPatania note: Eaves are the lower edges of a roof where it meets or overhangs the wall.

Be no higher than the lowest of the existing roof peak or 4 metres above ground
Not extend beyond the side or principal elevations
Be built only on hard surface that existed on or before 24 July 2023, or has been in place for at least 10 years

Minimum room sizes

The rooms in the existing building must comply with the Nationally Described Space Standard. That states that:

A single bedroom requires at least 7.5 square metres and 2.15 metres width
A double bedroom needs at least 11.5 square metres, with the main double bedroom at least 2.75 metres wide
The floor to ceiling height must be 2.3 metres for at least 75 per cent of the gross internal area

Those figures exclude any proposed rear extension but include building operations. In other words, each home must meet the NDSS within the converted shell itself. You can’t rely on the new rear extension to make under-sized rooms compliant.

Green belt land

In some cases, Class Q permitted development rights may also apply to conversions on green belt land. Eligibility for a Class Q barn conversion depends on the barn being on agricultural land as defined in the planning regulations.

You have to meet specific criteria for this though, which we detail below.

WindsorPatania link: Grey belt planning explained: What it means for developers and investors

Eligibility and exclusions

To be eligible for Class Q permitted development, you need to pass a number of tests.

Site and date tests

The site must be part of an established agricultural unit and have been used for agricultural purposes on 24 July 2023. If it becomes no longer part of that unit after that date, you need to wait at least 10 years before you can develop it.

After withdrawal of a site from a unit, no-one must have used it for a non-agricultural purpose since.

You also can’t use Class Q if there has been Class A(a) or Class A(b) development on the unit in the 10 years before you want to develop under Class Q.

In other words, erecting or extending a a farm building or excavations or engineering works such as new tracks or hardstanding

You may also be interested in: Paragraph 84e: A breakthrough to unrivalled countryside homes

Protected land, access and tenancy

Class Q does not apply to listed buildings or buildings on article 2(3) land including:

Conservation areas
National Landscapes (formerly Areas of Outstanding Natural Beauty)
National Parks
The Broads
World Heritage Sites
Sites of Special Scientific Interest (SSSI)
Safety hazard areas
Military explosives storage area.

The site cannot be or contain a scheduled monument.

The building must have suitable existing access to a public highway.

Where there’s an agricultural tenancy in place, the landlord and tenant need to give written consent. You can’t use Class Q if the farm tenancy ended less than a year before work starts. This is unless both sides agreed in writing that the land wasn’t needed for farming anymore.

Gaining prior approval permission

The local planning authority assesses specific matters when you apply for prior approval. Your submission must address each relevant test and satisfy the assessor.

The seven (eight) tests

For Class Q(a) and Class Q(a)+Q(c), your application needs to pass the following seven tests:

Transport and highways impacts: Show that vehicles can get in and out safely, with clear visibility at the entrance. You may need on-site turning space for farm or emergency vehicles and sensible parking arrangements.
Noise impacts: Make sure the home won’t be exposed to high noise levels from farm activity, machinery or roads. If there’s any risk, explain how you’ll manage it with simple measures.
Contamination risks: Include a basic desk study to flag any past use of fuel, chemicals, or asbestos. Say how you’ll handle it if contamination is found.
Flooding risks: Confirm the flood risk zone and set out basic drainage or flood resilience steps if needed.
Location or siting: Show why the location works for housing. It shouldn’t be next to anything that makes it clearly unsuitable, like strong odours or intensive livestock units.
Design or external appearance: Keep the rural feel. Use consistent openings and materials so the building still looks like an agricultural structure, not an over-domesticated house.
Light: Prove that every habitable room will have adequate natural light

There is an extra test for Class Q(a)+Q(b)+Q(c) on the impact of the proposed extension on the amenity of any adjoining premises. With this, you include elevations and sections that show no harmful loss of light, privacy or outlook for neighbours.

Include with your prior approval application

When applying to your council, make sure you send the following in:

A written description of the development proposed, including any building operations
How many dwellinghouses you’re proposing
A plan showing the site and the proposed development
Your contact address and email
Any fee required

Share whether previous Class Q development has happened within the established agricultural unit. Include dwelling numbers and cumulative floor space in these prior developments, too, in your statement.

The decision period is 56 days from when the authority receives your application. If the authority does not notify you of their decision within 56 days, you can go ahead. You must complete the development within three years of the approval date.

WindsorPatania: your partners in Class Q barn conversions

The new regulations have made it easier than before to convert agricultural buildings into residential use. The extension of permitted development rights offered to former agricultural buildings is welcome. Expect a new wave of modern barn homes to come forward as developers revisit sites once ruled out.

Standard barn conversions typically focus on preserving original features, materials, and historic character. The current trend is for modern living spaces, open plan and blending the traditional and contemporary. Work with our architects on creating the space you want that wins planning and building control approval.

We provide end-to-end architecture service for your barn conversion, including: