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Class Q Planning Blog

Navigating the process of applying for Planning Permission and effectively presenting your Class Q project or barn conversion can be a complex task. Local Authorities have their unique ‘Development Plan’ with diverse policies, making it challenging and time-consuming to understand and comply.

As an architectural design and consultancy firm based in Devon, our goal is to simplify this process by handling all aspects of the application and, whilst we can’t guarantee the final result, we make use of our knowledge and skills to maximise the chances of a positive outcome.

Here, we break down the process of securing planning permission for a Class Q architectural design project.

Permitted Development Rights

Certain agricultural buildings can be converted into a dwelling, or multiple dwellings, without formal Planning Permission through the use of Class Q permitted development rights. Unlike other Permitted Development right, such as Householder rights, there are multiple hoops to jump through for a Part Q conversion, and the project still needs to go to the Local Authority for a Prior Approval Application.


It is, however, a fantastic option for getting a dwelling out in the countryside – something that is usually an impossible task.


The first point is to check the eligibility of the building versus the Part Q legislation. The eligibility checklist is as follows:


  • The building must have been in agricultural use on 20th March 2013, or in agricultural use within 10 years before applying for the change of use – whichever is the lesser. This needs to be proven with factual information such as invoices, accounts, business related letters or photographs.

  • The building must not be listed, be part of any listing, or be a scheduled monument.

  • The building must not be sited in a Conservation area, Area of Outstanding Beauty, World Heritage site, National Park, site of special scientific interest or safety hazard area.

  • The building(s) can be split into a maximum of 5 residential dwellings. A combination of large and small dwellings is permissible but only up to three of them can be ’large’. The ‘large’ dwellings cannot have a cumulative floor area greater than 465 sqm and any small dwellings cannot have a floor area greater than 100sqm each.

  • You need permission from any current agricultural tenants, and permission cannot be granted if a tenancy has been terminated within 1 year, unless both the tenant and landlord agree in writing it is no longer needed for agricultural uses.

  • The proposed conversion must not be any larger than the existing building and no extensions of any kind are permitted.

  • The conversion can include the installation or replacement of windows, doors, roofs, exterior walls and services, and the partial demolition of any part of the building. The regulations state that this is “to the extent reasonably necessary for the building to function as a dwellinghouse”. Due to the ambiguity of this statement, and the term ‘conversion’, many Planning Authorities take differing views and so there is often conflicting advice on what can be converted. As a general rule of thumb, the existing building needs to have a complete roof, solid floor, and surrounding walls, though the walls themselves can have large openings. For specific advice on this, please arrange for a site visit from one of the team so that the existing building can be inspected and an opinion provided.

  • The building must be structurally capable of the conversion. No new or reinforcing structures are permitted to facilitate the conversion. Separate independent structures within the building are permitted, for example a mezzanine floor. An inspection report from a structural engineer is usually required to quantify and confirm the viability of the existing structure.

  • The converted building must be at least 37sqm in order to comply with national minimum space standards for a dwelling.

Prior Approval Process

If it is clear that the building is suitable for conversion, the next step is to apply for the development under a Prior Approval application. During the Prior Approval process the building and proposals are scrutinised by the Local Authority, who decide whether or not they agree that the proposals conform to the legislation. Alongside this, the Local Authority will also look at several other factors. These include:


  • Transport and highways impacts – will the conversion exacerbate problem junctions or access?.

  • Noise impact – will the conversion negatively impact neighbouring properties?

  • Contamination risks – is the existing building storin or involved with contamination?

  • Flooding risks – is the building within a floodplain and will it be safe for any occupants? If the existing building is within a flood risk area, a third party consultant will need to carry out a Flood Risk Assessment and potentially local flood modelling to remove or counter any concerns.

  • Is the location of the building impractical or undesirable? Due to case law on this area, this would only be used in extreme circumstances and is unlikely to be a reason for refusal.

  • The design and external appearance of the building – this simply means the Local Authority want the proposed conversion to match the existing building as closely as possible, for example, using timber cladding or blockwork steel roofing, all retained or replaced with similar finishes.


Following a successful approval of the Prior Approval application, the Local Authority will condition that the conversion must be completed within 3 years of the approval date. This is an important piece of information, particularly if the building is to be sold or the construction delayed in any form. The development may also be liable for CIL or similar new dwelling Council fees.

From Class Q Conversion to New Dwelling

It has been proven nationally under case law that an approved Class Q development can be used as a ‘fallback’ position. This ‘fallback’ means that the Local Authority cannot use their usual arguments against having a new house in the countryside as they are forced to accept that a dwelling will be there regardless.


There are several landmark cases which set the clear precedent that replacing existing agricultural buildings with new houses can be accepted, through a Full Planning Application, as long as the new proposals positively contribute to the development and surroundings. For example less visual impact, more coherent development or better neighbour interaction.


It is also possible to ‘mix and match’ Class Q approvals with other forms of approval to argue for a more coherent new development. This option should always be considered as a long-term goal for any Part Q project as it has the potential to substantially increase the value and amenity of any development and present an unencumbered building plot in the countryside.


Appeals and case law are always changing the interpretation of the Part Q legislation and so it is always worth discussing a Class Q project with one of our team.


Do you have an agricultural building?

If you have a barn or agricultural building that you think may be suitable for a Class Q conversion and would like some further guidance, get in touch to arrange a free site visit.