Barn Conversions: A Guide to Class Q Permitted Development
Published Date: October 2026
Architect and Director at WDA, Jonathan Turvey, explains the opportunities and considerations surrounding Class Q permitted development rights, and how they can provide a route to transforming redundant agricultural buildings into new homes.
An underused or redundant agricultural building may offer an opportunity to create one or more new homes. Class Q Permitted Development provides a route for changing the use of qualifying buildings without making a full planning application.
The rules are detailed, covering the building’s agricultural use, location, size and the work required for the conversion. An application for prior approval must also be submitted to the local authority before development can begin.
In this guide, we explain the current Class Q process in England, which buildings may qualify, how many homes can be created and the main restrictions you need to understand before moving forward.
How the Class Q process works
Class Q is set out in the Town and Country Planning (General Permitted Development) (England) Order 2018. It provides a permitted development route for changing the use of qualifying agricultural buildings to create homes, encouraging the reuse of existing structures.
Although a full planning application is not required, approval is not automatic. A prior approval application must be submitted to the local authority, setting out the proposed changes and demonstrating that the development meets the Class Q requirements.
The local authority will normally have 56 days to determine the application, although a longer period may be agreed where necessary. Class Q applies in England and is not available in Wales.
Which buildings can qualify for Class Q?
Not every agricultural building will qualify. Barns, cowsheds and grain stores are common examples, provided they meet the relevant requirements and are structurally capable of conversion.
The building must form part of an established agricultural unit and have been in agricultural use on or before 24 July 2023. If it was brought into agricultural use after this date, 10 years must have passed before it can be considered for Class Q.
If the building was constructed under agricultural permitted development rights, you will need to wait 10 years before undertaking a Class Q conversion. The same restriction can apply where Class A or Class B of Part 6 has been used to construct or extend an agricultural building within the previous 10 years.
Previous and current use also matter. If the building has been used for another purpose, such as keeping horses or storing non-agricultural items, Class Q might not apply and full planning permission would be required.
How many homes can be created under Class Q
A proposed development can involve one agricultural building or several buildings on the same agricultural unit, and a single building can also be divided into more than one home.
Since May 2025, the rules allow up to 10 new homes across the agricultural unit, with a maximum combined floor area of 1,000 sqm. This is the total allowance across all the buildings and homes included in the proposal.
No individual home can be larger than 150 sqm. The homes do not all need to be the same size, but their combined floor area must remain within the 1,000 sqm limit. If 10 homes are proposed, the average floor area would be limited to 100 sqm per home, although the sizes could vary across the development.
These are maximum allowances rather than an automatic entitlement. The proposal must still meet the relevant Class Q requirements and receive prior approval.
What building work is allowed?
Approval can cover the change of use of the agricultural building and work that is reasonably necessary for its conversion. This may include replacing the roof and creating new window and door openings.
The current rules also allow a single-storey extension of up to four metres at the rear of the building. The extension must be built on a hard surface that existed before 24 July 2023. If the hard surface was created after this date, it must have been in place for at least 10 years.
This is a route for converting an existing agricultural building. It does not provide permission to demolish the building and replace it with a new home. Other work that would increase its size, including porches and further extensions, would require a separate planning application.
The extent of the work will depend on the existing building and proposed design. The local authority will consider whether the alterations fall within the Class Q requirements as part of the prior approval process.
Main restrictions to consider
This permitted development right only allows an agricultural building to be changed to residential use. If you want to use the building for another purpose, a different planning route would be required.
It is not available for listed buildings or buildings within the grounds or curtilage of a listed building. It also cannot be used within Conservation Areas or National Landscapes, previously known as Areas of Outstanding Natural Beauty.
Where these restrictions apply, residential development may still be possible, but it would need to be explored through a different route, such as a full planning application.
There may also be cases where the building qualifies, but its limitations prevent the best use of the building or wider site. In these circumstances, an approved scheme may provide a fallback position for a separate planning application.
Preparing a Class Q application
A successful application requires the building, proposed work and supporting information to meet the relevant requirements. The following areas should be considered before an application is submitted.
Architectural design: An experienced architect can develop a design that works with the existing structure while meeting the requirements for suitable habitable spaces.
Site appraisal: The wider site should be reviewed alongside the building, including access, services and potential environmental effects. Identifying these points early can help shape the proposal and the information required.
Early discussions with the local authority: Speaking with the local planning authority can help clarify its expectations and identify potential concerns before the application progresses.
Specialist reports: Structural assessments, ecological surveys, measured building survey, flood risk statement and other expert reports may be needed to demonstrate that the conversion is viable and address matters raised by the site or proposed development.
Bringing this information together creates a clearer application and helps the local authority understand how the proposal meets the Class Q requirements.
Other design considerations
Meeting the Class Q requirements is an important part of the process, but there are wider design considerations that may influence the proposal.
Sustainability: The conversion may provide opportunities to improve energy efficiency and introduce sustainable design features while reusing the existing agricultural structure.
Heritage character: Although Class Q cannot be used for listed buildings or buildings within their grounds, some qualifying agricultural buildings may still have historic or local significance. The design can respond to the building’s existing character while introducing the changes needed for residential use.
WDA’s heritage experts can advise where a building’s history or character requires particular attention.
Planning your next step
Class Q can provide a valuable route for bringing an underused agricultural building back into use. However, its potential will depend on the building’s history, condition and location, as well as the number of homes and alterations proposed.
If you have an agricultural building that may meet the criteria, WDA can review the opportunity and advise on the most appropriate next step. This may involve a Class Q prior approval application or, where the permitted development restrictions limit what can be achieved, exploring the fallback position.
Find out more about our Class Q permitted development and fallback planning service.
For wider architectural support with the design and development of a conversion, visit our Barn Conversion Architects page.
Alternatively, call us to arrange a no-obligation discussion about your building or site.
Find out more…
Read more from Architect Jonathan Turvey on ways to improve a Class Q approval utilising the ‘fallback position’.
Published 22 October 2026
