Permitted Development Calculator

Understanding Permitted Development Rights

Permitted Development (PD) rights allow certain changes of use without needing full planning permission. For property developers, the most valuable PD right is Class MA - which enables conversion of commercial buildings (Class E) to residential (Class C3) through a simpler prior approval process.

How This Calculator Works

Our Permitted Development Calculator assesses your project against current PD regulations:

1. Location Assessment Enter the property address and local authority. This is crucial because PD rights vary significantly by area - many London boroughs and town centres have Article 4 directions that remove PD rights entirely.

2. Use Class Verification Confirm the building's current use class and how long it has been in that use. For Class MA, the building must have been in Class E use for at least 2 continuous years before the application date. We check if the proposed change qualifies for PD.

3. Building Details Enter the gross internal area, number of storeys, and target unit count. Class MA has floorspace limits and minimum space standards that affect feasibility. We calculate preliminary GDV and build costs based on your inputs.

4. Constraint Checking This is where many PD hopes fail. We check for: - Article 4 Directions: These remove specific PD rights. If an Article 4 applies to your site and use change, you need full planning permission. - Listed Building Status: PD rights do not apply to listed buildings - you need listed building consent. - Conservation Areas: PD may still apply but prior approval assessment is more stringent. - Flood Zones: Additional assessment required but doesn't block PD.

What Class MA Prior Approval Involves

Even with PD rights, you still need prior approval from the local planning authority. They can only refuse on specific grounds:

Transport and Highways: Impact on the road network, parking provision, and pedestrian safety.

Contamination Risks: Whether the site is contaminated and remediation needed for residential use.

Flooding: Whether the building is in a flood risk area and appropriate mitigation.

Noise: Impact of commercial noise sources on proposed residents and vice versa.

Natural Light: Whether habitable rooms will have adequate natural light.

Fire Safety: Adequate means of escape and fire service access.

Unlike full planning, the council cannot refuse based on design, density, housing mix, affordable housing contributions, or general planning policy.

Prior Approval vs Full Planning

Prior Approval (Class MA): - Application fee: £334 per application (not per unit) - Determination period: 56 days - No affordable housing requirement - No S106 contributions - No CIL in most cases (depends on local charging schedule) - Limited grounds for refusal - Cannot refuse based on design or appearance

Full Planning: - Application fee: £578 per dwelling - Determination period: 8-13 weeks (often longer) - Affordable housing required (typically 35%+ on larger schemes) - S106 contributions likely - Full CIL liability - Council can refuse on any material planning consideration - Extensive supporting documents required

When PD Rights Don't Apply

Several constraints remove PD rights entirely:

Article 4 Directions: Local authorities use these to protect employment areas, town centres, or residential character. Always check the local planning portal - many are not obvious from looking at the building.

Listed Buildings: Any grade listing removes PD rights. You need listed building consent plus planning permission for change of use.

Time in Use: The building must have been in qualifying use (Class E) for at least 2 years before application. If vacant or recently converted, PD may not apply.

Cumulative Floorspace: There are limits on how much floorspace can convert under different PD classes. Check if previous PD has been used on the site.

Safety Hazard Areas: Buildings within certain distances of hazardous installations may be excluded.

Making the PD Route Work

For successful PD conversions:

1. Verify PD Eligibility Early: Check Article 4 status, use class history, and any previous PD on the site before making offers.

2. Gather Evidence of Use: Obtain business rates records, utility bills, and photographs showing continuous Class E use for 2+ years.

3. Commission Early Reports: Transport statements, contamination assessments, and noise surveys take time. Start these during due diligence.

4. Design for Space Standards: All habitable rooms need natural light and adequate floor areas. Poor layouts lead to prior approval refusal.

5. Consider Neighbours: While not a formal requirement, addressing neighbour concerns about parking, bins, and overlooking helps smooth the approval process.

6. Plan for CIL: Some local authorities charge CIL on PD conversions. Check the charging schedule and factor into appraisal.