What permitted development rights allow - and what they don't
Permitted development (PD) rights allow certain changes of use and building works without requiring full planning permission. The developer must obtain prior approval in many cases - a lighter-touch assessment by the local authority - but this is not equivalent to a planning application and carries lower refusal risk.
The most commercially significant PD rights for property investors and developers:
- Class MA: Commercial buildings (Class E use - offices, retail, light industrial, restaurants, gyms) to residential. Maximum 1,500 sqm. Building must have been vacant for 3+ months.
- Class Q: Agricultural buildings to residential. Up to 5 dwellings per holding, maximum 865 sqm in total. Must be structurally capable of conversion.
- Class O (now subsumed into Class MA): Office-to-residential conversions were the original commercial PD right. Now incorporated into the wider Class MA framework.
- Residential extensions: Single-storey rear extensions (Class A), loft conversions (Class B), outbuildings (Class E). Prior approval required for larger extensions.
Prior approval - the process and what it assesses
Prior approval is a notification to the local authority that you intend to exercise a PD right. The authority must assess specified matters within a defined timeframe (typically 56 days for Class MA). If prior approval is granted - or if no response is received within 56 days - the works can proceed.
What Class MA prior approval assesses: Transport and highways impact; contamination; flooding; noise from commercial premises; impact of loss of commercial floor space; natural light for habitable rooms; fire safety.
What it does not assess: Design, appearance, or the general principle of residential use. These are the matters assessed in full planning - and their exclusion is what makes PD significantly less risky than a planning application.
Prior approval refusal: The local authority can refuse if the specific matters are not satisfied. They cannot refuse on grounds of design or their preference for commercial retention unless the specific matters provide a basis. Legal challenge of an unreasonable refusal is available.
Development appraisal for a PD project
A PD development appraisal follows the same structure as any development appraisal but with different cost assumptions:
- Lower planning risk costs: No planning application fees, no planning consultant costs at full planning scale, faster commencement following prior approval.
- Higher conversion cost uncertainty: PD conversions - particularly agricultural (Class Q) - can reveal structural issues that a new build does not. Contingency of 20-25% of works cost is prudent for PD conversions.
- GDV: Based on RICS-comparable sold prices for equivalent residential units in the same area. Rural agricultural conversions (Class Q) often produce higher GDVs than urban commercial conversions (Class MA) due to the premium buyers pay for unique rural residential units.
- Profit margin: Development finance lenders require minimum 20% profit on GDV. Below this, finance becomes harder to secure and pricing rises. PD projects should target 25%+ margin at appraisal to maintain viability after contingency is consumed.
Finance structure for permitted development projects
Stage 1 - Land or commercial acquisition: Bridging finance for the acquisition, typically 60-70% of the commercial or agricultural value. Lower LTV than residential reflects the more complex security.
Stage 2 - Prior approval period: Bridge runs during prior approval determination. The lender must be informed that the project is PD-dependent and the bridge term must accommodate the prior approval period.
Stage 3 - Development finance: Once prior approval is confirmed, development finance replaces the acquisition bridge. Works are funded in tranches against monitoring surveyor certification. Total facility typically covers 80-90% of the development cost (loan-to-cost).
Stage 4 - Exit: Either sale of completed units (most PD projects are built for sale) or refinance onto BTL mortgages for rented retention. Development exit bridging can bridge the gap between works completion and sales completion.
Agricultural PD conversions (Class Q) - specific considerations
Class Q permits the conversion of agricultural buildings to residential use, subject to prior approval and specific criteria. Key points:
- The building must be structurally capable of conversion - the external envelope (walls, roof) must be capable of supporting conversion without fundamental rebuild. A structural engineer's pre-purchase assessment is essential.
- Permitted operations: Class Q allows only interior works and modifications to the exterior necessary for the conversion. Demolition and rebuild is not permitted under Class Q - if the structure cannot support conversion, the right does not apply.
- Unit limits: Up to 5 dwellings on a single agricultural holding, maximum 865 sqm combined gross floor area across all conversions.
- Farmhouse connection: The agricultural building must be genuinely linked to agricultural use - not an urban fringe plot with a nominal agricultural building. Local planning authorities are alert to artificial arrangements.
- Class Q units: Converted agricultural buildings frequently produce unique and premium residential units - barn conversions with high ceilings, exposed beams, and rural settings - that command a significant price premium over standard residential in the same area.