What is Class Q permitted development?

Class Q sits in Part 3 of Schedule 2 to the General Permitted Development Order 2015. It gives a national permission to change the use of an agricultural building to a dwellinghouse, so you do not need a full planning application for the change of use itself.

The right covers three things:

• Q(a): the change of use on its own.
• Q(b): the change of use plus a limited extension.
• Q(c): the change of use plus the building works reasonably necessary to convert or extend it, such as new windows, doors, roof, walls and services.

It is not a free pass. Before any work starts you must apply to the local planning authority for prior approval, and the scheme has to meet every condition in the Class Q legislation. The right applies in England only. Wales, Scotland and Northern Ireland have their own rules.

The Class Q rules since May 2024

Class Q was rewritten by an amendment order that came into force on 21 May 2024. The main limits are now:

• Number of homes: up to 10 across the original agricultural unit.
• Total floor space: no more than 1,000 square metres of new homes in total.
• Size of each home: no more than 150 square metres.
• Extensions: a single-storey rear extension of up to 4 metres. It cannot go beyond the side or front of the building.
• Space standards: each new home must meet the nationally described space standard.

The agricultural use test

The building must have been part of an established agricultural unit on 24 July 2023. If it left agricultural use before then, it can still qualify if it has not been used for anything else since. If it came into agricultural use after that date, it must have been in that use for at least 10 years before the conversion starts.

The old rule that a building had to be used solely for agriculture has gone. This helps farm buildings that saw some minor non-farm use in the past.

Where Class Q does not apply

• Article 2(3) land: conservation areas, National Parks, National Landscapes (formerly AONBs), the Broads and World Heritage Sites.
• Sites of Special Scientific Interest, safety hazard areas and military explosives storage areas.
• Listed buildings and scheduled monuments.
• Land under an agricultural tenancy, unless both landlord and tenant agree in writing.

Which buildings qualify?

The test is about use, not appearance. A barn used to house livestock, store feed or keep farm machinery is agricultural. A building that looks like a barn but was used for something else is not.

Stables and equestrian buildings

Stables used to keep horses for riding, livery or leisure are generally treated as equestrian use, not agriculture, so they usually fall outside Class Q. The picture can be different where horses are kept as part of farming, for example grazing on working farmland. If in doubt, a planning consultant or a lawful development certificate can settle it before you spend money on drawings.

Condition of the building

Class Q allows the works reasonably necessary to convert a building. It does not allow you to knock it down and build a house in its place. Councils often refuse schemes where the frame cannot take the new loads or where most of the walls and roof would need replacing. A structural survey early on is money well spent.

Location and siting

The council can also refuse prior approval if the location or siting makes the change to a home impractical or undesirable. That is about the site itself, such as access, or a working farm next door, not about whether the countryside is a sustainable place for housing in general.

How the prior approval process works

A prior approval application is shorter than a full planning application, but it still needs proper plans and supporting reports. The council can only assess the matters listed in the order:

• Transport and highways impacts.
• Noise from nearby commercial premises.
• Contamination risks.
• Flooding risks.
• Whether the location or siting makes a home impractical or undesirable.
• The design and external appearance of the building.
• Natural light in all habitable rooms.

How long it takes

The council has 56 days from receiving a valid application to decide. Under paragraph W(11), if it does not notify you of a decision in that time, the development can go ahead. In practice, check that the application was validated and keep a record of the dates.

After approval

The conversion must be completed within three years of the prior approval date. Building regulations approval is separate and still needed. Many barns also need a bat or wildlife survey before work starts.

What it costs

Application fees are set nationally and change from time to time, so check the current figure with your council or the Planning Portal. The bigger costs usually sit around the application: drawings, structural and ecology surveys, a flood assessment where relevant, and a planning consultant if you use one.

Class Q or full planning permission?

Class Q is usually quicker and more certain than a full application, because the council can only look at the listed matters. It is not always the right route.

Class Q tends to suit

• A structurally sound barn outside protected land.
• A scheme that fits within the size limits and a 4 metre rear extension.
• Owners who want a decision without arguing the case for housing in the countryside.

Full planning permission tends to suit

• Barns on protected land, such as a conservation area or National Park.
• Listed barns, which also need listed building consent.
• Schemes that need a larger home, bigger extensions or major rebuilding.

Some owners secure Class Q prior approval first and then apply for full planning permission for a better design. An existing prior approval can be a material consideration, sometimes called a fallback position, though how much weight it carries is up to the council. The same idea of converting existing buildings under permitted development runs through our guide to commercial to residential conversion.

Running a converted barn as a holiday let

A rural barn conversion can suit short lets. Guests book countryside stays for space, character and quiet, and a well-finished barn can charge more per night than a standard cottage.

Class Q creates a dwellinghouse. Before you plan around short lets, check with your council whether anything in your approval, or your local plan, affects letting it to guests. Then look at the numbers:

• Finance, since holiday let lending differs from standard buy-to-let. See our guide to holiday let mortgages.
• Running costs, from cleaning and linen to utilities and insurance, covered in the costs of running a holiday let.
• Whether the property will pay council tax or business rates.

Our guide to buying a holiday let covers the wider checks. If you would rather not run guests yourself, Houst offers holiday let management across the UK, and our income calculator gives an estimate for your address in a couple of minutes.