How to get agricultural buildings without planning permission in England

GPDO Part 6: agricultural permitted development explained

Part 6 of the GPDO covers agricultural buildings and operations. The key permitted development classes are:

Class A: Agricultural buildings and works on units of 5 hectares or more. Class B: Agricultural buildings and works on units between 0.4 and 5 hectares (more restricted, often requires prior approval). Class Q: Change of use of agricultural buildings to residential (C3) via prior approval (barn conversions).

The most relevant for most farmers/smallholders is Class A, which can allow substantial agricultural buildings without full planning permission—if you meet the tests.

The 5-hectare threshold (critical test)

For Class A PD to apply, the agricultural unit must be 5 hectares or more.

What's an 'agricultural unit'? It's the land used for agricultural purposes (farming, horticulture, forestry) that is managed as a single holding. If you own multiple parcels in the same business, they can count together toward the 5-hectare threshold—but they must be in genuine agricultural use.

If your unit is under 5 hectares, you fall under Class B, which has tighter restrictions and often requires prior approval for buildings over 465m².

Size and location limits for agricultural buildings under PD

Even if you meet the 5-hectare threshold, your building must meet these conditions:

For units 5+ hectares: Buildings up to 465m² floor area can often be permitted development (subject to prior notification for buildings over certain thresholds). Buildings over 465m² need full planning permission.

Height limits: Typically 12m maximum height (but lower in some contexts). Must be at least 25m from a classified road.

Siting: The development must be reasonably necessary for the purposes of agriculture within that unit.

• Prior notification (28-day procedure): For certain agricultural buildings, you must notify the LPA 28 days before starting. The council assesses siting, design, and external appearance.
• Designated areas: PD rights for agricultural buildings are more restricted in National Parks, AONB, conservation areas, and Sites of Special Scientific Interest.

When planning permission is required

You need full planning permission for agricultural buildings if:

• The agricultural unit is under 5 hectares and the building exceeds Class B limits
• The building exceeds PD size limits (over 465m² on a 5+ hectare unit)
• The building is not 'reasonably necessary' for agriculture (councils can challenge this)
• You're in a designated area and PD rights are restricted or removed
• The building will be used for non-agricultural purposes (storage, workshops, residential)
• You want to convert an agricultural building to a dwelling outside the Class Q route

Class Q barn conversions (agricultural to residential)

One of the most popular uses of agricultural PD: converting redundant barns to homes under Class Q prior approval.

Key conditions for Class Q:

Class Q is NOT automatic. The council can refuse prior approval if the building fails the tests (particularly the structural soundness test, which is strict).

Prior approval fee: £120 per dwelling for Class Q. Timeline: Council has 56 days to determine.

• The building must have been in agricultural use on 20 March 2013 (or last in agricultural use before that date)
• The building must be structurally sound and capable of conversion without substantial demolition/rebuild
• Maximum of 5 dwellings and 465m² floor space per unit
• The council assesses: transport, contamination, flooding, noise, design, and external appearance

Common expensive mistakes with agricultural buildings

These mistakes cost agricultural landowners thousands:

• Building before checking the 5-hectare threshold—if your unit is under 5 hectares, you don't have Class A PD rights
• Assuming any building on agricultural land is automatically 'agricultural'—the building must be reasonably necessary for agriculture on that unit
• Using an 'agricultural' building for non-agricultural purposes without permission—storage, vehicle repairs, residential use all need consent
• Starting a Class Q barn conversion without checking structural soundness first—the building must be capable of conversion without substantial rebuild
• Not following the 28-day prior notification procedure where required—this invalidates PD and makes the building unauthorized
• Building in the Green Belt and assuming 'agriculture = automatic approval'—agricultural buildings can be acceptable but still need to meet tests

Real costs and timelines

Agricultural building costs: Vary hugely. Simple portal-frame barn: £20,000–£60,000. More complex agricultural structures: £60,000–£200,000+.

Planning fees if full permission required: £258 (householder if ancillary to dwelling), £578+ (full application for commercial/independent agricultural buildings).

Prior notification (Class A/B): No fee for the notification, but councils may charge for pre-app advice.

Class Q prior approval (barn conversion): £120 per dwelling. Conversion build costs: £80,000–£250,000+ depending on size and spec.

Timeline: Prior notification 28-day determination. Class Q prior approval 56-day determination. Full planning permission 8–13 weeks.

Step-by-step: agricultural building compliance workflow

Follow this to stay compliant:

• Step 1: Measure your agricultural unit—is it 5+ hectares?
• Step 2: Check if you're in a designated area (National Park, AONB, SSSI)—PD rights are restricted
• Step 3: Determine if the building is 'reasonably necessary' for agriculture on your unit
• Step 4: Check size against Class A/B limits (typically 465m² threshold for PD)
• Step 5: Follow 28-day prior notification procedure if required before starting
• Step 6: Use PlanWiser's Property Checker to identify constraints (Green Belt, conservation area, flood risk)
• Step 7: Use PlanWiser's AI Advisor to understand whether your building qualifies as agricultural PD or needs full permission