How do you convert a Barn under Permitted Development?

How can you convert a Barn under Permitted Development


Changes to planning law means investing in a barn conversion and using permitted development rights could be a good investment, but, here’s Architect Garry Thomas’s summary of all you need to know before parting with cash.


Changes to Permitted Development (PD) Rights introduced in early April 2014 have transformed the development landscape for anyone wishing to undertake a barn conversion in England (not applicable to the rest of the United Kingdom as it currently stands).

But at Thomas Studio we find people are less aware of recent Further amendments to permitted development rights, which took effect on 6 April 2018, that include an allowance for up to five new homes to be created from existing agricultural buildings rather than the previous maximum of three.

Here’s a short video about Canwood Gallery, a farm diversification project.

Here’s what’s Changed?

These recent amendments mean it’s now possible to convert existing agricultural buildings – barns for example – into homes without needing to expressly apply for planning permission, as had previously been the case.

This will mean that Permitted Development Rights can allow homeowners to carry out building work to their homes without needing to apply for planning permission from the local authority and have traditionally been used to enable minor extensions, loft conversions and the creation of outbuildings to be carried out without the need for notification.

Here’s the Details?

The Barn Conversion clause comes about as part of a new Class – MB – into Part 3 of the Second Schedule of the General Permitted Development Order. This new class authorises change of use of a building and any land within its curtilage from use as an agricultural building to a use falling within Class C3 – dwellings. It also authorises building operations ‘reasonably’ necessary to convert the building to residential use.

  • The site must have been used solely for agricultural use;
  • The barn must have existed on by 20th March 2013 (no building new barns!). New barns can be built and converted into homes but must exist as solely agricultural buildings for at least 10 years;
  • The total floor space of your barn to be converted must be no more than 465m² – if the barn is bigger, you’ll only be able to convert to a maximum of 465m²*;
  • The 465m² can be divided into five* separate dwellings;
  • If the site is subject to an agricultural tenancy, landowners must have the express consent of their tenants.

*effective from 6 April 2018. You can find out more here Find out more about these changes to PD rules for agricultural buildings.

How Much of Your Barn Can You Rebuild?

Class MB permits reasonable building operations to convert a barn into a house, but only within the envelope of the existing structure. It permits partial demolition and rebuilding of the barn, but the extent of this allowance will probably be decided by case law over time.

Most experts believe it unlikely that flimsy Dutch barns or glasshouses could be simply knocked down and replaced with a new house (even if it were to mimic the appearance of the existing) although this is something that will be established as homeowners and local authorities dispute the detail.

However, significant improvement to the existing fabric, including new windows, even new walls as required, will be permitted under MB.

At Thomas Studio we have found some Local Authorities confuse themselves over PD rights and the suitability of a barn conversion in planning terms, particularly with Dutch barns that don’t have any sidings or walls. Given this it can sometimes be best to avoid permitted development rights altogether and approach the Local Authority with a full planning application. We have developed a good portfolio of barn examples where this is best explored.

What Does Permitted Development Exclude?

Class MB – the barn conversion clause – doesn’t apply on any site within so-called Article 1(5) land, i.e. National Parks, Conservation Areas, Areas if Outstanding Natural Beauty etc.)

Here’s what you Need to do Before You Convert a Barn?

Local Authorities on the whole don’t like permitted development as it removes their powers to determine what would otherwise be a planning application process. Therefore, there are lots case law examples where authorities have been called to task for failing to allow permitted development. Given this legal background unfortunately the more controversial elements of Permitted Development, Class MB is subject to what’s known as a Prior Notification procedure.

Prior Notification, what is it?

Prior notification came into force in 2013. Under this planning change, single-storey, rear residential extensions can be built up to 8m in depth (6m for a semi or terrace), provided that boundary neighbours are first informed or given ‘prior notification’.

As long as there are no objections, or any objections received have no planning merit, then a Certificate of Lawful Development is issued.

The 2013 changes also allowed for the change of use of buildings from office use (B1) to residential (C3).

Prior Notification Extended to Agricultural Buildings

In April 2014, the rules governing ‘prior notification’ was expanded to include Class Q. This will allow change of use from agricultural buildings to ‘dwelling houses’, subject to certain ‘conditions’.

In addition, the agricultural building must be capable of functioning as a dwelling house without serious structural changes (although some operations would be permitted).

It is actually possible for an agricultural conversion to bring about no more than five residential units, with a maximum floor space of 465m3. *

*Effective from 6 April 2018

Before starting, you must apply to the local authority to establish whether you will need to receive prior approval for:

  • transport
  • noise impact
  • contamination
  • flood risk
  • and ‘Whether the location or siting of the building makes it otherwise ‘impractical’ or ‘undesirable’ for the building to change from agricultural use to residential use.’

As you can see, the emotive words ‘impractical’ and ‘undesirable’ give the local authority power to veto your development (although their decision must comply with the policies in the National Planning Policy Framework). In many ways, this makes the Prior Notification process within Permitted Development a planning application by another name. It also causes Local Authorities to make more of an issue of transport, noise, flooding etc. to justify refusing to allow the conversion of a barn under PD.

It is still too early to gauge the impact of the Prior Notification clause; however, as barns are often in isolated rural areas, one can imagine the issues of sustainability being raised as a potential objection by local authorities.

Likewise, Prior Notification is also required for the local authority to decide whether they need to have prior approval on the design and external appearance of the building. Again, any decision must be met within the context of the NPPF, but it’s not too difficult to conclude that this is just another form of planning application. Under the Prior Notification procedure, the local authority does have the right to impose conditions on the development. But there is always appeal and the UK’s direction of travel is government wants to build more houses.

PD processes can result in the Local Authority forming a negative view of the barn conversion before you proceed to a full planning application – again, it may be wise to avoid the PD process altogether and go straight to a full planning application. At Thomas Studio we assess the suitability of a PD approach and will advise you which strategy is best for your development.

Do You Have a barn in mind?

Architect Garry Thomas is willing to give you 15mins if his time for free to help you understand if your potential project is worth investing in.

Book your free 15-minute call back with Architect Garry Thomas here