Permitted development vs planning permission: which route do you need?

What is permitted development?

Permitted development rights are types of work you can carry out without needing to apply for planning permission. Planning Portal explains that PD rights are granted by Parliament through the General Permitted Development Order (GPDO) and cover common home improvements.

Key PD categories for homeowners:

The crucial point: PD is not 'no rules.' It's a specific set of automatic permissions with tight conditions. Break the conditions and you're in unauthorized development territory.

• Single-storey rear extensions (up to 3m/4m depth, or 6m/8m with prior approval)
• Loft conversions (within 40m³/50m³ volume limits)
• Outbuildings (single storey, max 2.5m eaves, max 3m/4m overall height)
• Roof lights and windows (within existing roof plane)
• Driveways and hardstanding (with drainage provisions)
• Solar panels (subject to size and position limits)
• Fences and gates (1m high facing highway, 2m elsewhere)

What is planning permission?

Planning permission is a formal consent from your local planning authority allowing you to carry out development. You apply, pay a fee, the council assesses against policy, and they issue a decision (approval with conditions, or refusal with reasons).

When you need planning permission:

Planning permission gives you more flexibility—you can propose things that aren't PD—but it costs money, takes time (8–13 weeks), and can be refused.

• Your project doesn't fit any PD category
• Your project exceeds PD limits (too tall, too deep, wrong position)
• Your property is a flat (most PD rights don't apply to flats)
• You're in a designated area with restricted PD rights (conservation area, National Park, AONB)
• PD rights were removed by Article 4 direction or planning condition
• You're building a new dwelling or creating a separate unit
• You're changing use of land or buildings between use classes

Key differences: PD vs planning permission

Here's the practical comparison:

Application required? PD: No application needed (but follow rules). Planning permission: Yes, formal application required.

Cost? PD: £0 (though you can get an LDC for £129 for proof). Planning permission: £258+ depending on application type.

Timeline? PD: Immediate (once you've confirmed compliance). Planning permission: 8–13 weeks typically.

Certainty? PD: You must self-assess compliance (risk if you get it wrong). Planning permission: Council decision provides formal certainty.

Flexibility? PD: Rigid limits and conditions. Planning permission: More flexible, can propose anything (but might be refused).

Who decides? PD: Automatic (by law, if you meet conditions). Planning permission: Council officer or planning committee decides.

When permitted development is the right choice

Choose PD when:

Best practice even for PD: Get a Lawful Development Certificate (LDC) for £129 before starting work. This gives you formal proof that your PD interpretation is correct and protects you from enforcement.

• Your project clearly fits within PD limits and you're confident of compliance
• You're on a tight timeline and can't wait 8+ weeks for planning permission
• You want to avoid application fees and professional costs
• Your property is a house (not flat) in a non-designated area
• You're willing to design within PD constraints rather than pushing boundaries

When planning permission is the right choice

Choose planning permission when:

Planning permission costs more and takes longer, but it can unlock projects that PD can't accommodate—and it gives you a formal decision with legal weight.

• Your project exceeds PD limits but you still want to proceed
• You're in a designated area or your PD rights are restricted/removed
• You want design flexibility beyond PD constraints
• You're doing a project that has no PD route (new dwelling, major change of use)
• You want formal council approval for resale certainty
• Your project is borderline PD and you'd rather have official approval than enforcement risk

The hybrid route: prior approval

Some PD categories require 'prior approval'—a middle ground between automatic PD and full planning permission:

Prior approval means: The principle is established by PD, but the council assesses specific matters (design, highways, amenity, etc.). Cheaper and faster than full planning permission, but not as simple as pure PD.

• Larger home extension (6m/8m rear extensions): Prior approval required, 42-day determination, £120 fee
• Office to residential (Class MA): Prior approval required, 56-day determination, £120 per dwelling
• Barn conversion to residential (Class Q): Prior approval required, 56-day determination, £120 per dwelling

Common mistakes that cost thousands

These errors waste money and time:

• Assuming 'small project = no permission'—PD has strict limits; exceed them by 10cm and you're unauthorized
• Not checking if you're in a conservation area or Article 4 zone before relying on PD—can lead to enforcement
• Building first, checking later—retrospective applications are not guaranteed approval
• Not getting an LDC for PD work—causes problems at resale when buyers' solicitors question lawfulness
• Assuming flats have the same PD rights as houses—they don't
• Confusing 'no planning permission' with 'no building regulations'—building regs are separate and often still required for PD work

Real costs comparison

Permitted development route: £0 for the PD right itself. Optional: £129 for LDC for proof. Still need: Building regulations (£400–£1,200), architect/drawings if desired (£800–£3,000+).

Planning permission route: £258 (householder) to £578+ (new dwellings, change of use). Plus: Drawings (£800–£3,000+), Planning statement (£500–£2,000 if consultant), Supporting surveys (£500–£5,000+ depending on constraints), Building regulations (£400–£1,200).

Total typical costs: PD route: £1,000–£5,000 (mainly building regs and drawings). Planning permission route: £2,000–£12,000+ (application, professional fees, surveys).

Step-by-step: how to decide which route

Follow this decision workflow:

• Step 1: Check property type—house or flat? (Flats have limited PD rights)
• Step 2: Use PlanWiser's Property Checker to identify constraints (conservation area, Article 4, listed building)
• Step 3: Identify your project type and check if it has a PD category
• Step 4: If PD exists, check if your design meets ALL the limits and conditions
• Step 5: If yes to PD, consider getting an LDC (£129) for proof, or proceed under PD
• Step 6: If no to PD (doesn't fit, exceeds limits, or restricted), prepare planning application
• Step 7: Use PlanWiser's AI Advisor to confirm your understanding before committing to either route