Building Regulations and Planning Permissions

Guide to Planning Permission for Barn Conversions: Permitted Developments under Class Q

Aspiring self-builders have historically been discouraged from attempting to design their dream home in rural green-belt locations, due to the complex planning rules that surround these types of projects. However, for those interested in converting an agricultural barn into a modern, light-filled home, the Class Q permitted development criteria may be the way to go.

What does the Class Q criteria cover?

Class Q was introduced in 2014 to lay out the criteria for permitted developments in rural areas, including green belt zones. This section of regulations states that certain agricultural buildings may undergo substantial works to convert them into habitable dwellings.

For landowners looking to build a new residence in the countryside, this piece of regulation paves the way for a scenic barn conversion project – arguably a much simpler route to take than attempting to obtain planning permission for a new build home under Paragraph 80 (previously 79).

Class Q allows for the following:

  1. The change of use of a building and any land within its curtilage that is classified as an agricultural building, to use within Class C3 (dwelling houses).
  1. Building operations that can be deemed as “reasonably necessary” to convert the building to a Class C3 dwelling house.

slim sliding aluminium doors in a class q barn conversion 500

Barn conversions vs rebuilds

The design of the project is limited to what is considered as “reasonably necessary” works to adapt the old building. With this in mind, permission will be rejected if the design is seen to be a full rebuild from the ground-up.

The change of use should therefore always be presented as a conversion that retains some elements of the old building where possible, rather than a complete rebuild. However, the difference between the two terms can be subjective, with some local authorities taking a stricter stance on the definition than others.

Following the 2018 update of the Class Q regulation, it is no longer required that the agricultural building must be structurally strong enough to bear the loading caused by the conversion works.

This means that structural reinforcement is acceptable – such as replacement walls, roofs and drainage systems. Professional advice is recommended for each project, if it isn’t clear whether the conversion might be classified as a rebuild.

It is also worth noting that internal works – such as creating a mezzanine or adding a first floor – are not considered to be a development. As such, internal changes are not restricted by Class Q.

barn conversion permitted development class q double height sliding glass doors 725

Extensions are not permitted

The permitted development criteria make it clear that the converted building(s) may not have a footprint that exceeds the dimensions of the original agricultural building.

This doesn’t necessarily mean the end of the line if converting a very small barn – to create a larger property, however, full planning permission should be sought in order to grant a much higher degree of flexibility in the design, rather than going down the Class Q route.

On the other hand, you don't have to stop at just 1 new property if converting a very large agricultural building. Class Q also allows for the creation of up to 5 converted dwellings, equating to up to 865m2 in total, on one plot of land. The new dwelling(s) can be created from one or more agricultural buildings on the plot, so long as the total footprint isn’t exceeded. The new house(s) can be divided as follows:

  1. Smaller dwelling houses – 5 units; no more than 100m2 each.
  1. Larger dwelling houses – 3 units; no more than 465m2 each.
  1. Up to 5 homes comprising of a mix of larger and smaller homes, with neither exceeding the maximum floorspace for each type.

class q barn conversions with bespoke slim framed aluminium glazing 650

Exceptions to the permitted development criteria

Although Class Q allows for barn conversions in the countryside and green-belt land, there are certain areas that the legislation does not apply to. These include:

  • Conservation Areas
  • National Parks
  • Areas of Outstanding Natural Beauty
  • World Heritage Sites
  • Sites of Special Scientific Interest
  • Sites containing scheduled monuments and listed buildings

The legislation also poses several limitations on the buildings that can be converted. These can be summarised as the following:

  • Buildings cannot be converted if they are not part of an agricultural business on or prior to March 2013, or if they haven’t been part of an agricultural business for a period of at least 10 years from March 2013.
  • Agricultural use is defined as a business that also makes a profit, meaning that buildings used to grow produce as a hobby or other recreational use would not classify as Class Q criteria.

sliding glass walls in a modern barn renovation and conversion 750

The application process

If your barn conversion project fits the Class Q criteria, a prior approval application would need to be submitted in order to determine whether the development is acceptable. The local authority will look at several aspects for this, including:

  • Impact on the local roads and highways
  • Noise impact
  • Risk of contamination
  • Risk of flooding
  • The design and external appearance of the build, including how these fit into the local environment
  • The practicality and desirability of the building location, e.g. barns with no road network in the near vicinity, or with chemical plants and dangerous farm equipment nearby, would likely be rejected
  • The provision of enough natural light in all habitable rooms

The application will also require proof that the previous building use meets the dates and criteria set out in the Class Q legislation.

contemporary barn conversion class q rules architectural glazing 565

Planning a barn conversion?

IQ Glass have years of experience ­­­designing and installing bespoke glazing for sensitive projects of this nature. For expert advice on your project, get in touch with the team at 01494722880 or

Further Reading

Planning permission: Para 79

Guide to permitted developments

Creating a modern barn conversion