Class Q Barn Conversion Projects – What is Class Q Permitted Development?

Planning expert Julia Riddle reveals how Class Q permitted development rights can make it easier to convert a barn or agricultural building into a bespoke, countryside home

by Julia Riddle

30th January 2025

Class Q is the provision that allows for the change of use of an agricultural building to a residential property, without the need for full planning permission. These allowances have been in place for some years now, however the parameters of what can be achieved have changed over time, giving greater development opportunities. The most recent updates came into effect in May 2024.

The provision is set out in the Town and Country Planning (General Permitted Development) Order 2015 (as amended). These regulations also outline the updated parameters for what can be undertaken under Class Q.

The legislation can provide great opportunity for the delivery of new homes in rural areas, particularly where they might not normally be approved through a full planning application. It’s worth considering this route when looking for sites and considering options for development in the country – it could be the best way to realising your dream home, with the added benefit of a more streamlined approval process.

Here, I’m exploring the kind of properties and projects eligible for Class Q conversion and the key considerations to bear in mind.

What Criteria Do You Need to Meet to Qualify for Class Q?

There are certain conditions that must be met for a building to be eligible for conversion through this route. Principally, the building must be part of an agricultural unit. The changes to the rules in 2024 have given more flexibility as to the use of the building itself – it’s not uncommon for agricultural structures to have been re-purposed in some way.

For example, and the updated legislation no longer requires the property to be in a state of agricultural use. There are some nuances around this which should be checked over in each unique case.

Class Q Barn Conversion Projects – What is Class Q Permitted Development?

After his plans to build from scratch were rejected by the planners, Build It reader Jamie Davison realised he could convert a barn his brother had purchased, under Class Q rules. The stunning new home features double-height glazing, vaulted ceilings and timeless interiors

It’s important to note that these provisions do not apply where a building is listed, or located in a national park, area of outstanding natural beauty or a conservation area. Additionally, the structure must be substantially intact – a formal survey is likely to be needed to demonstrate or prove this as part of a planning process.

If the structure was built under permitted development rights (under Part 6 of the GPDO) then it’s not eligible for change until it is over 10 years since it was erected. Additionally, if a barn was built, even with planning permission, it will need to have been in place for 10 years from July 2023 before it qualifies for conversion.

This Class Q barn conversion designed by VESP Architects involved reconfiguring a series of redundant, single-storey buildings, turning them into one large home. The material palette includes modern larch timber cladding and local granite to complement the rural surroundings

If the associated agricultural land is subject of a tenancy, the tenant needs to be given one year notice or there needs to be an agreement that the land is no longer required for agricultural use. This arrangement can’t be based only on the desire to pursue Class Q.

There are some fairly complex and detailed transitional arrangements, plus various circumstances where some changes may still be possible under the pre-May 2024 regulations. So, if you’re unsure if your building qualifies, it’s best to seek professional advice concerning your specific circumstances to ensure compliance.

Are There Any Limitations When Converting a Barn Under Class Q?

There are limits to the extent of development that can be achieved through this route, allowing for up to 10 new homes to be built on a single farm holding. There are also size thresholds that apply as follows:

The floor space of any dwellinghouse developed under Class Q cannot exceed 150m².
The cumulative number of separate dwellinghouses cannot exceed a total of 10.
The cumulative floor space of the dwellinghouses cannot exceed 1,000 m² in total.

This Class Q barn conversion designed by VESP Architects features an open-plan interior, with clever lighting features designed into the beams overhead

An extension can be sought of up to 4m to the rear of the building, if there is existing hard standing. This can only be achieved as part of the Class Q submission and cannot be added to a structure previously converted through this route where this was not part of the original submission.

Under these provisions, 10 units can be spread across more than one building in any agricultural unit. The Class Q rights also allow for:

Installation or replacement of external walls, doors, windows, roofs, drainage and any services – under the condition that these should not protrude more than 0.2m from the existing building.
Partial demolition as required.
Internal structural works, including insertion of mezzanine or upper floors, internal walls etc.
If these parameters are not adhered to, the development will not be accepted through the Class Q route and will require full planning permission.

The process requires specific information to be provided to the council. If you’re not sure if your building or plans meet the qualifying criteria, it would be beneficial to seek professional advice or some confirmation from the council through a pre-application process. The submission of a prior approval application to your local planning authority to secure the Class Q change must be done before any works are undertaken.

This barn received Class Q permitted development rights rights to convert it into a four-bed property

When you submit your prior approval, the council will look at the design and appearance of the changes proposed; it’s always assumed that in this unique type of development, these will be in keeping with the agricultural look of the building and surrounding character of the area.

In the case of a Class Q proposal, the council will also review access, potential highway issues, flood risks, contamination matters, availability of water and sewage treatment arrangements, impact on the surrounding area and the provision of adequate light to all habitable rooms. This process takes up to 56 days. After which, if there’s no decision, the change is accepted. Although, it’s always worth seeking confirmation before starting works.

Julia Riddle

Julia Riddle is a planning consultant with experience in advising on a range of commercial and residential development. She runs Castle Planning and has written guidance to inform the national approach to Custom and Self Build and is a member of the Right to Build Task Force.