Building on Agricultural Land in Dorset: What’s Allowed (and What Definitely Isn’t)
- Rosenkelly Architectural Design
- Jan 10
- 4 min read
Exploring whether you can build on farmland in Dorset? In general, any development that meets the legal definition of “development” needs permission. Fortunately, England’s planning rules include permitted development (PD) rights for rural land – but these are tightly limited. Farmers can erect new agricultural structures (like barns or silos) under Part 6 of the GPDO (Classes A–E) if their farm is large enough, yet these rights do not cover new houses. The main PD route to a rural home is Class Q (barn conversion), which only permits converting an existing farm building into a C3 dwelling and necessary internal work. Any other proposals, or any development that breaks Class Q limits, will require full planning permission.
Permitted Development on Your Farm
New farm buildings (Class A–E GPDO): On units of 5 hectares or more, you can build agricultural structures up to 465m² (plus a small extension) without planning permission. These allow for equipment, storage, livestock, etc., but not housing. Converting such buildings into homes or using greenfield land for a dwelling needs full permission.
Class Q barn conversions: This special PD right lets you change an existing farm building into a home. Under Class Q you can convert an agricultural building to a Class C3 dwelling and carry out “building operations reasonably necessary” for that conversion. Recent updates (May 2024) even allow up to 10 homes (total under 1,000 m²) subject to conditions.
Key limitations: You must keep the building’s existing footprint and height, and retain most of its structure. Class Q does not permit demolition and “rebuild” or raising roofs beyond their original height. The building must have been in agricultural use by 20 March 2013 (or brought into use before then and not changed to non-farm use). You can’t simply extend into new ground; only the structure itself counts.
Eligible structures: Class Q only covers existing agricultural buildings. Open-sided barns, modern sheds, or very dilapidated frames might not qualify as a ‘building’ under GPDO rules. The work must be “reasonably necessary” to make the structure a home (e.g. installing insulation, windows, floors). Essential engineering works (new foundations, major structural changes) are usually not covered.
Location restrictions: Class Q rights are restricted in protected areas. You cannot use Class Q in National Parks, World Heritage Sites (e.g. Jurassic Coast), Sites of Special Scientific Interest, or conservation areas. Importantly for Dorset, Class Q does not apply in AONBs (much of Purbeck and Cranborne Chase). Farms within these landscapes will need full planning consent for any new dwellings or conversions.
Flood risk: If the building sits in Flood Zone 2 or 3, Class Q requires a site-specific flood risk assessment. (In Zone 3 this usually rules out Class Q.) Check the Environment Agency’s flood map early on – if your site is at risk of flooding, you may need to persuade planners with extra reports.
Prior Approval: Even where Class Q applies, you must apply for prior approval from the LPA (Dorset Council) before work. This asks the council to check details like access, traffic, contamination, and heritage impact against Class Q rules. In practice, Dorset Council encourages a positive, proactive approach: they offer pre-application advice to guide rural proposals and will consider if the scheme meets all Class Q conditions. If any criterion fails, the LPA can refuse the prior approval.
Dorset-specific Considerations
Dorset’s rural planning context adds extra layers. The entire county is now managed by Dorset Council, which covers areas from the New Forest border through Purbeck and down to the Jurassic Coast.
If your land falls within one of Dorset’s AONBs (e.g. Dorset AONB or Cranborne Chase AONB), you should plan on seeking full consent, as Class Q is barred there. Even outside AONBs, adjoining AONB influence and the Jurassic Coast World Heritage Site status encourage sensitive design. If a farm straddles these areas, extra surveys (landscape, ecology) will be needed.
Flooding is a concern in parts of Dorset (e.g. lower-lying vales or coastal plains). If the barn is in Environment Agency Flood Zone 2 or 3, expect to include a site flood risk assessment with any application. Where flood risk is high, Council and Environment Agency input will be strict. In lower-risk (Zone 1) areas, Class Q conversion is easier from a flooding perspective.
Dorset Council’s planning department advises applicants and is generally positive in approach. They offer a pre-application advice service so you can check feasibility early. This means you can discuss with planners whether Class Q is appropriate or if you need full permission, and get feedback on potential issues (heritage, highways, ecology). Using their guidance can save time and uncertainty.
Working with Rosenkelly Architectural Design
Given the complexity and case-by-case nature of rural planning, early expert advice is invaluable. Rosenkelly Architectural Design is a local, ARB-registered architecture firm specialising in rural and coastal Dorset projects. We know the local landscape and planning teams well.
Our friendly, pragmatic approach means we can assess your site (AONB status, flood risk, ecology, etc.), advise on the best route (Class Q vs full planning), and guide you through the paperwork or prior approval process. We prepare clear drawings, speak with the council on your behalf, and look for creative solutions that fit within permitted limits.
Many successful barn conversions start by engaging an architect like Rosenkelly at the concept stage, so designs align with Class Q constraints from the outset.
Disclaimer: This article is for general information only and does not constitute legal or planning advice. Every site and proposal is unique, and permitted development rights may vary with changing laws or local rules. For a definitive assessment of your rural land and building plans, consult with qualified planning and architectural professionals.
Ready to explore your farm’s potential?Contact Rosenkelly Architectural Design today for a friendly discussion about your Dorset site. We can review your land, explain Class Q options, and help you take the next step with confidence. Let us guide you through the countryside planning process.
