Agricultural buildings and Class Q

This article explains the facts about Class Q planning permission, which allows conversion of agricultural buildings into houses. It examines:

  • the definition of Class Q
  • Class Q permitted development
  • eligibility for prior approval
  • the qualifying criteria

To get familiar with the key considerations, dive in!

Development potential?

What is Class Q planning permission?

In an initiative to increase housing in rural areas, Class Q regulations were introduced as a form of permitted development in 2014. Class Q consent allows a redundant agricultural building and land within its curtilage to be converted into a house (for instance, a barn conversion) without the need for full planning consent via a prior approval application process, providing certain criteria are met.

While this makes it a less demanding route to achieving planning consent, there are restrictive conditions involved.  A Class Q application is no faster but is less costly than submitting a full planning application; it requires less detail, however, technical information is needed to satisfy planners about the future use of a building.

Details will need to be given on matters including the location or siting of the building, the change of use, noise, contamination, additions externally, highways impact and flood risk. Crucially, applicants must also be able to demonstrate that the existing agricultural building was used for agricultural purposes on a specified date. 

Class Q regulations were introduced via the Town and Country Planning (General Permitted Development) (Amendment and Consequential Provisions) (England) Order 2014 as Class MB. It was renamed Class Q in the subsequent Town and Country Planning (General Permitted Development) Order 2015;Schedule 2, Part 3. 

A redundant agricultural building.

What is permitted development?

Permitted development is a national grant of planning permission found in the Town and County Planning (General Permitted Development) (England) Order 2015 (as amended) (GPDO 2015), which allows certain building works and change of use without the need for a full planning application. Permitted development may be subject to satisfying specific conditions set by a planning authority regarding design and obtaining prior approval may be necessary before starting any scheme. 

Prior approval

Subject to the qualifying criteria, an application for prior approval can be made to the planning authority which has a set time in which to respond of 56 days. If a response is not forthcoming within this time, planning permission is deemed granted providing that the scheme qualifies. Transport and highways issues must be satisfied along with other requirements including the practicality of the location, noise impact, design, contamination, water drainage and flooding risk.

Qualifying criteria

To satisfy Class Q criteria the existing building in question must have been in agricultural use as part of an established agricultural unit on 20th March 2013; if it came into agricultural use after that date, a 10-year period must elapse before it can qualify for Class Q regulations: this can be proved by showing the local planning authority the agricultural holding number.

Class Q permitted development is not allowed in conservation areas, Areas of Outstanding Natural Beauty, World Heritage Sites, Sites of Special Scientific Interest, within the curtilage of a scheduled monument or listed buildings or in national parks, however, green belt sites are not excluded.

Class Q planning details

The scope of Class Q is clarified in paragraph 105 of the government’s Planning Practice Guidance (PPG). A 2018 amendment distinguishes between larger and smaller houses; for larger houses (above 100 square metres) the scheme allows for three separate houses with a cumulative total floor space not exceeding 465 square metres.

For smaller houses (under 100 square metres), a maximum of five are permitted with a cumulative floor area of 500 square metres. With a combination of larger and smaller houses, the maximum number allowed is five: the floorspace of a larger house cannot exceed 465 square metres, and the cumulative total floorspace for the scheme is restricted to 865 square metres.

Reasonable changes

It is important to remember that the external dimensions of an existing agricultural building cannot be increased and a garden cannot exceed the building’s footprint (Extension Architecture, 2019). To overcome difficulties with a scheme which makes it otherwise impractical, reasonable changes can be made.

These include installing and replacing windows, doors and the roof and insulation works; building operations can also involve connecting a water supply, drainage, electricity, gas and other services reasonably necessary to create a home while retaining a rural character.

Often, a structural appraisal is needed to ensure the building can support conversion work without too much adaptation. Replacing foundations or load-bearing flooring is not allowed; if major changes are required, full planning consent may be necessary, however, partial demolition of the existing building is allowed.


The question of what works constitute a `conversion’ have led to difficulties with Class Q planning approvals; the condition that building operations are permitted which are `reasonably necessary’ to convert agricultural buildings into houses often proves difficult to interpret.

Nationally, around 60% of Class Q planning applications are refused, (CLA, 2015), which is often due to differences in interpreting the qualifying criteria between an applicant and a local authority; these may relate to noise, the impact of a scheme on local amenity and the requirement to ensure adequate natural light in all habitable rooms.

A robust, well-reasoned application is needed for the best chance of success and applicants should not assume that Class Q is an easy route to obtaining planning permission. 


Extension Architecture. 2019. UK planning permission. [Online]. Available from: (Accessed September 17th 2021)

CLA. 2021. UK news. [Online]. Available from: (Accessed September 17th 2021)

Planning Insight. 2021. Class Q. [Online]. Available from: (Accessed September 17th 2021)

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