Agricultural building prior notification under Part 6
Part 6 lets a farmer erect a working building without a full application, but only on a unit of five hectares or more and within tight ground area, height and distance limits.
Agricultural building prior notification is the procedure in Part 6 of Schedule 2 to the General Permitted Development Order 2015 that lets a farmer put up a working building without a full planning application. It is permitted development, so you are not asking whether the building is acceptable in principle. You are asking the council to decide whether it wants a say in the siting, design and external appearance, and it has 28 days to tell you.
Two thresholds decide which class you are in. Class A covers agricultural land in a unit of five hectares or more. Class B covers units of at least 0.4 hectares but less than five. The difference matters because Class B does not permit a new building at all.
What Class A permits on a unit of five hectares or more
Class A allows works or a building reasonably necessary for the purposes of agriculture within the unit. That covers a general purpose barn, a grain store, a livestock building, a slurry store, hardstanding, a private track and the plant and machinery that goes with them.
The five hectare test attaches to the agricultural unit, not to the field you are building in. A unit is the land occupied as a unit for agriculture, and it can be made up of scattered parcels held on different tenures. So a holding of six hectares in three blocks qualifies even if the block containing the building is only one hectare. Conversely, a single 20 hectare field that has been split into separately occupied plots may no longer be one unit at all. Get the unit boundary evidenced before anything else, because everything downstream depends on it.
"Reasonably necessary for the purposes of agriculture" is the second gate, and it is the one that gets tested. A building sized for the stock or the crop the holding actually carries reads as agricultural. A steel portal frame twice the size of anything the holding could fill invites the council to say the real purpose is storage for something else. Where the justification is thin, a short Planning Statement setting out the holding, the enterprise and why the building is needed does more good attached to the notification than produced later under enforcement.
The ground area, height and road limits
Class A falls away if any of these are exceeded:
- Ground area of more than 1,000 square metres, counting any other building or works within 90 metres that was put up within the previous two years. This is the limit people trip over, because a shed erected 18 months ago three fields away can still count.
- Height above 12 metres, reduced to 3 metres where any part of the development is within 3 kilometres of the perimeter of an aerodrome.
- Any part within 25 metres of the metalled part of a trunk or classified road.
- Provision, extension or alteration of a dwelling. Part 6 never permits housing.
- A building, structure or excavation for livestock, or for the storage of slurry or sewage sludge, within 400 metres of the curtilage of a protected building.
A protected building is a permanent building normally occupied by people, ignoring buildings on the same agricultural unit. Your own farmhouse does not count against you. The neighbour's cottage does.
Cumulation over two years is worth a spreadsheet rather than a memory. Keep a running log of every Part 6 building, its ground area, its date and its distance from the others, because the council will reconstruct it from aerial photography if there is ever a dispute. The treatment of smaller holdings under Class B uses the same 1,000 square metre figure but a much shorter list of permitted works.
The extension and alteration tests
Not every Part 6 building needs a notification. The prior approval procedure applies to the erection of a building, an extension or alteration of one that the Order labels "significant", the formation or alteration of a private way, an excavation or deposit of waste material covering more than 0.5 hectares, and the placing of a tank in any waters.
The Order defines both. An extension counts where the cubic content of the original building would be exceeded by more than 10 per cent. An alteration counts where the height of the original building would be exceeded. Below those figures the works are still permitted development but no notification is needed, which is why replacing cladding or adding a lean-to often needs nothing at all.
Measure cubic content, not floor area. A 10 per cent cubic increase on a tall building is a larger footprint than people expect, and on a low building it is smaller.
The 28 day period and how it runs
The procedure is deliberately light. You apply to the authority for a determination as to whether its prior approval will be required to the siting, design and external appearance of the building, with a written description of the proposed development, the materials to be used, a plan showing the site, and the fee set by the fees regulations. That fee is modest and is indexed annually, so take it from the current schedule.
From there, three things can happen, and you must not start until one of them has:
- The authority writes to say prior approval is not required. You may build, in accordance with the details you gave.
- The authority writes to say prior approval is required. You then wait for that approval and build in accordance with it.
- Twenty-eight days pass from the date of your application without the authority making a determination or notifying you of one. You may build, in accordance with the details you gave.
The third route is not a loophole. It is the design of the system, and it is why the description and plan you submit have to be accurate. Whatever you build has to match what you told them, and a building put up materially differently from the notified details is not permitted development. Once the position is settled, the development has to be begun within five years, and the detail of the five hectare notification route sets out the paperwork in more depth.
Siting, design and external appearance
Where the authority does reserve approval, its powers are narrow. It can address siting, design and external appearance of a building, the siting and means of construction of a private way, and the siting and design of an excavation or deposit with its restoration. It cannot refuse the principle, and it cannot require a different enterprise.
In practice the requests are predictable. Move the building behind an existing group rather than out into open field. Change a light grey profiled sheet to a dark olive or slate grey. Set the ridge lower. Plant a hedge along the exposed flank. Where the holding sits in a National Landscape or near a listed farmstead, expect all four.
Offer the mitigation yourself. A notification that shows the building tucked against an existing yard, with a colour specification and a native hedge line, is often returned with a letter saying approval is not required. One that shows a pale building isolated on a ridge attracts a reservation and an extra eight weeks.
Livestock buildings and slurry stores
Slurry and livestock carry the extra restrictions. Beyond the 400 metre rule, a separate condition bites where any Part 6 development is carried out within 400 metres of the curtilage of a protected building: the building, structure or excavation must not then be used for livestock or for slurry storage. So a general purpose barn built close to a neighbour's house is lawful, and filling it with cattle is not.
Water pollution rules run alongside. New or substantially altered slurry and silage storage has to be notified to the Environment Agency in advance under the silage, slurry and agricultural fuel oil regulations, with construction to the standards those rules set. Planning and pollution control are separate consents, and neither one excuses the other.
Using the building for something else later
A Part 6 building carries a condition that it be used for agriculture. Park a haulage lorry in it, rent it to a joiner, or store a caravan fleet, and you have a material change of use that needs permission.
Two routes exist for going further, and both have dates attached. Class R allows a change to flexible commercial use for a building in agricultural use as part of an established unit on 3 July 2012. Class Q allows a change to dwellings where the building was used solely for agriculture on 20 March 2013, or for ten years before the change where it came into use later. A building you put up under Part 6 last year meets neither, and no amount of intention at the notification stage changes that. The conditions attached to Class R flexible commercial use repay a read before you design a building you hope to convert.
If the long-term plan is diversification, say so and apply for planning permission for the use you actually want. Enter your postcode on PlanScope to see which supporting documents a farm building or diversification proposal is likely to need.
This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. A lawful development certificate is the only formal way to confirm that works are lawful. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
Does the five hectare test apply to the field or the whole farm?
To the agricultural unit, which is the land occupied as a unit for agriculture and can consist of several scattered parcels. A six hectare holding in three blocks qualifies even where the building sits in a one hectare block. Evidence the unit boundary and occupation before you rely on Class A.
What is the maximum size of building Part 6 allows?
A ground area of 1,000 square metres, and that figure includes any other building or works within 90 metres put up in the previous two years. Height is limited to 12 metres, or 3 metres within 3 kilometres of an aerodrome perimeter. Exceed any of those and a full planning application is needed.
What happens if the council does not reply within 28 days?
You may proceed, building strictly in accordance with the description, materials and plan you submitted. The 28 days run from the date of your application. This is how the procedure is designed to work rather than an oversight, so the accuracy of the submitted details is what protects you afterwards.
Can I build a slurry store near a neighbouring house?
Not under Part 6 if any part is within 400 metres of the curtilage of a protected building, meaning a permanent building normally occupied by people other than on your own unit. A separate condition also prevents any Part 6 building within that distance being used for livestock or slurry. Notify the Environment Agency before new storage is used.
Can a Part 6 building be converted to a house later?
Not through Class Q. That class requires the building to have been used solely for agriculture on 20 March 2013, or for ten years where the agricultural use started later. A recently erected Part 6 building fails that test, and Class R flexible commercial use has its own qualifying date of 3 July 2012.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.