Planning Rules
Agricultural Buildings Permitted Development: Part 6 Rules (2025)
Farmers and rural landowners can erect agricultural buildings without planning permission using Part 6 of the GPDO 2015. Here’s what’s allowed, how large, and what needs Prior Approval.
⏱ 7 min read📅 Updated June 2025🏠 England only
Quick Answer
Agricultural buildings are permitted development under Part 6 — up to 1,000m² without Prior Approval on large units
Part 6, Class A of the GPDO 2015 permits agricultural buildings, structures and works on agricultural units of 5 hectares or more, without requiring planning permission. Buildings up to 1,000m² on units over 5ha can be erected without Prior Approval, provided they are not within 400m of a dwelling (other than a farmhouse on the unit), are not on a separate dwelling curtilage, and meet height and appearance conditions. On smaller units (between 0.4ha and 5ha), Class B applies with a 1,000m² limit on buildings but all operations require Prior Approval. Buildings for livestock or slurry storage within 400m of a protected building always require Prior Approval.
What Is Part 6?
Part 6 of Schedule 2 to the GPDO 2015 grants permitted development rights for agricultural operations. These rights recognise that farming requires flexibility to erect buildings, carry out engineering operations, and change uses without full planning permission.
Part 6 has two main classes:
- Class A: For agricultural units of 5 hectares (12.4 acres) or more
- Class B: For agricultural units between 0.4 hectares (1 acre) and 5 hectares
The key distinction is size — larger farms have more generous rights. In both cases, “agricultural unit” means agricultural land used for agriculture which is occupied as a unit for the purposes of agriculture. The land must be in active agricultural use, not just capable of it.
Class A: Agricultural Buildings and Works
Part 6, Class A permits the following on agricultural units of 5ha or more:
- The erection, extension, or alteration of a building
- The formation, alteration, or maintenance of private ways
- The carrying out of any engineering operations to drain agricultural land
- The carrying out of any operations (not involving development) on agricultural land
The most common use of Class A is erecting farm buildings — machinery stores, grain stores, workshops, straw barns, and covered yards. These buildings must be designed and sited so as to be reasonably necessary for agricultural purposes and must not significantly alter the established character and appearance of the building.
⚠️ “Reasonably necessary for agricultural purposes” is the key test Class A only permits buildings reasonably necessary for the purposes of agriculture within the agricultural unit. A building that would primarily serve non-agricultural purposes (storage for a commercial business, private workshops) would not qualify for Class A rights, even on a large farm.
Size Limits at a Glance
| Condition |
Detail |
| Maximum building floor space (Class A, 5ha+) |
1,000m² of agricultural buildings erected or extended in the previous 2 years |
| Maximum height |
3m (within 3km of an aerodrome); 12m otherwise — but see ‘reasonable necessity’ |
| 400m rule |
No new livestock building or slurry/sewage sludge storage within 400m of a protected building (dwellings etc.) |
| Design requirement |
Reasonably necessary for agriculture; must preserve established landscape character |
| Class B (0.4ha–5ha) floor space |
1,000m² but all operations require Prior Approval |
| Glasshouses (Class A) |
Permitted without restriction on floor space on 5ha+ units (Prior Approval still needed for glasshouses over 465m²) |
✅ 28-day rule: if the council does not determine a Prior Approval application for an agricultural building within 28 days of a valid application, Prior Approval is deemed granted. This is a fast determination period compared to Class Q’s 56 days.
When Prior Approval Is Needed
Prior Approval under Part 6 is needed for:
- Any new building, structure, or extension on a 5ha+ unit that exceeds 465m² of floor space
- Any building within 400m of a protected building used for livestock or slurry/sewage sludge storage
- Buildings on 5ha+ units that are 12m or more in height
- All buildings and works on 0.4ha–5ha units (Class B)
- Glasshouses on 5ha+ units that exceed 465m²
For Prior Approval applications under Part 6, the council can only consider: the siting, design, and external appearance of the building; the impact of transport on the highway network; and (for Class B) the impact on the rural character of the area.
Frequently Asked Questions
Do I need planning permission to build a barn?
Not necessarily — if the barn is on an agricultural unit of 5 hectares or more, it may be permitted development under Part 6, Class A of the GPDO 2015. Buildings up to 465m² can be built without Prior Approval (subject to the 400m rule and other conditions). Larger buildings require Prior Approval. If the farm is between 0.4ha and 5ha, Class B applies and all buildings require Prior Approval. The building must be reasonably necessary for agricultural purposes.
Can I build an agricultural building in an AONB or National Park?
Yes — Part 6 agricultural PD rights apply in AONBs and National Parks. However, in these areas (and other designated land), the PD rights are reduced: the Prior Approval threshold drops to 465m² (rather than 1,000m²) and the local authority has more scope to assess design and landscape impact. In National Parks and AONBs, agricultural buildings are commonly required to use traditional materials and siting to minimise landscape impact.
What counts as an agricultural unit for Part 6 PD rights?
An agricultural unit means agricultural land used for agriculture, occupied as a unit. The land must be in active agricultural use — it cannot be vacant land or land used for non-agricultural purposes. The 5ha threshold is measured for the whole agricultural unit, not just the land in a single field or parcel. If an agricultural unit is split across multiple plots all farmed together, they can be aggregated. The person using the land for agriculture (including as a tenant) occupies it as the agricultural unit for Part 6 purposes.
Can I convert an agricultural building built under Part 6 to residential use?
Not immediately — agricultural buildings erected under Part 6 cannot be converted to residential use (Class Q) within 10 years of being built. This is a specific condition to prevent farming PD rights being used to create building plots: someone cannot erect an agricultural building under Part 6 and then quickly convert it to a house using Class Q. After 10 years, if the building has been used for agriculture throughout, Class Q may apply.
More on Permitted Development Rights
Extensions, loft conversions, outbuildings, solar panels — our complete guide covers everything you can build without planning permission.
Read the Complete PD Guide →
