Planning Permission vs Permitted Development: Do You Need Permission?

You want to build an extension. Your neighbour says you need planning permission. Your builder says you don't. Your architect says "it depends."

Who's right?

The answer determines whether your project starts in 3 months (planning permission route) or 3 weeks (permitted development). It's the difference between £500 in council fees or nothing. Between neighbour consultation or building without asking.

Here's everything you need to know, explained without the legal jargon.

The Simple Version

Permitted development is a set of automatic permissions granted by government. You can build certain things without applying to the council—as long as your build meets strict criteria.

Planning permission is when you submit plans to your local council and they decide whether to approve or reject your proposal based on how it affects the area.

What You Can Build Under Permitted Development

These are the most common builds that qualify for permitted development if they meet the rules:

Single-Storey Rear Extension (Most Common)

You DON'T need planning permission if:

• Extension is no more than 4 metres deep (detached house) or 3 metres (attached/semi-detached)
• Maximum height is 4 metres
• Eaves are no higher than 3 metres
• No part is higher than the existing roof
• Doesn't cover more than 50% of land around the original house
• At least 2 metres from any boundary if over 3m high
• No verandas, balconies, or raised platforms
• Materials are similar to the existing house

Larger Single-Storey Rear Extensions (Temporary Permission)

There's a temporary permitted development right allowing deeper extensions:

• 6 metres deep for semi-detached/terraced houses
• 8 metres deep for detached houses

But: You must notify your neighbours. They have 21 days to object. If they object, the council reviews it.

Side Extensions

You DON'T need planning permission if:

• Single storey only
• No more than half the width of the original house
• At least 2 metres from boundary if over 3m high
• Maximum height 4 metres
• No part higher than existing roof

Loft Conversions

You DON'T need planning permission if:

• Additional volume no more than 40 cubic metres (terraced) or 50 cubic metres (detached/semi)
• No extension beyond the roof slope facing the road
• Materials similar to existing house
• No verandas, balconies, or raised platforms
• Side-facing windows are obscure-glazed

Outbuildings (Shed, Garage, Summer House)

You DON'T need planning permission if:

• Single storey only
• Maximum eave height 2.5 metres
• Maximum overall height 4 metres (dual pitch roof) or 3 metres (any other roof)
• At least 2 metres from any boundary if over 2.5m high
• Not used as separate living accommodation

When You MUST Get Planning Permission

You need planning permission if:

• You've already used your permitted development allowance (you can only extend a certain amount before you need permission)
• You're in a conservation area (stricter rules apply)
• You're in a national park, AONB, or listed building
• Article 4 direction applies (council has removed permitted development rights in your area)
• Your extension exceeds the size limits above
• You're building a second storey (almost always needs permission)
• You're changing the use (e.g., garage to living room may need permission)
• You're building in front of the house (e.g., porch over 3m² or forward extension)

How to Check If Your Project Qualifies

Step 1: Check Your House Type

Permitted development applies to original dwellinghouses. Not flats, not maisonettes, not houses that have been converted into flats.

Step 2: Check for Restrictions

Call your local council planning department and ask:

• "Is my property in a conservation area?"
• "Are there any Article 4 directions affecting my address?"
• "Has permitted development been removed from my property?"

Step 3: Measure Carefully

Measure from the original house (as it was in 1948 or when first built), not the current footprint. You may need to check:

• Old planning applications (available from council)
• Title deeds
• Historical maps

Step 4: Calculate the 50% Rule

No more than 50% of the land around the "original house" can be covered by buildings. This includes:

• The house itself
• Any extensions
• Outbuildings, garages, sheds

Lawful Development Certificate (The Safety Net)

Even if your extension qualifies for permitted development, you might want a Lawful Development Certificate (LDC).

What it is: Official confirmation from the council that your project doesn't need planning permission.

Why you'd want one:

• Protects you if someone challenges your build later
• Makes selling the house easier (solicitors love official documents)
• Proves to mortgage lenders the extension is legal
• Peace of mind your builder got the measurements right

Cost: Typically £130-£200 (half the cost of planning permission)

Timeline: 8 weeks (same as planning permission)

Planning Permission: When You Need It

If your project doesn't qualify for permitted development, you need full planning permission.

What's Involved

1. Submit application with drawings, design statement, and fee (typically £258 for house extensions in 2026)
2. Neighbour consultation – Council notifies neighbours, they have 21 days to comment/object
3. Council assessment – Planning officer reviews against local plan policies
4. Decision – Approve, approve with conditions, or refuse (8 weeks typical)

What Council Considers

• Impact on neighbours – Overlooking, loss of light, overbearing appearance
• Character of area – Does it fit the street scene?
• Design quality – Materials, proportions, architectural style
• Access and parking – Is there adequate parking?
• Trees and ecology – Protected trees, bat roosts, etc.

Approval Rate

Nationally, 88% of householder planning applications are approved. If your architect knows the local area and designs appropriately, your chances are good.

Common Misconceptions

"Permitted development means I don't need any approval"

Wrong. You still need building regulations approval for structural safety, insulation, drainage, etc. Planning and building control are separate.

"My neighbour can block my permitted development extension"

Mostly wrong. Under normal permitted development, neighbours have no say. Under the larger extension scheme, they can object and trigger a council review—but objecting doesn't automatically stop you.

"I can build anything under 4 metres without permission"

Wrong. The 4m depth limit comes with 10+ other criteria you must meet. Don't assume size alone determines permission.

"Permitted development is quicker"

Usually true. You can start immediately (after building control approval). But if neighbours object under the larger extension scheme, it becomes similar to planning permission timelines.

What Happens If You Get It Wrong?

You build thinking you have permitted development rights. Council issues an enforcement notice.

Consequences:

• You must apply for retrospective planning permission
• If refused, you must demolish the extension
• Can't sell house with unapproved works
• Mortgage lenders won't lend on property
• Insurance may be void

The Practical Advice

If Your Extension is Clearly Within Limits

3m deep, 3.5m high, mid-terrace house, not in conservation area. You're fine. Build under permitted development. Consider an LDC for £150 peace of mind.

If You're Close to the Limits

3.9m deep on a 4m allowance. In a conservation area. Lots of previous extensions. Get professional advice. An architect or planning consultant can confirm whether you need permission.

If You're Over the Limits

5m deep extension, two-storey, or other non-qualifying factors. You need planning permission. Hire an architect who knows your local area—they'll design something the council will approve.

Track Your Build From Planning to Completion

Whether you're applying for planning permission or building under permitted development, Ted helps you manage every step—track costs, document progress, and keep your builder accountable.

Final Checklist

Before you assume permitted development applies:

1. ✓ I've checked my property isn't in a conservation area
2. ✓ I've confirmed there's no Article 4 direction
3. ✓ My extension is under the size limits
4. ✓ I've measured from the original house, not current footprint
5. ✓ I've calculated the 50% land coverage rule
6. ✓ I've confirmed materials match existing house
7. ✓ I've checked boundary distances
8. ✓ I'm still getting building regulations approval

If you can tick all boxes, you're good to go under permitted development.

If you're unsure about even one box, get professional confirmation before you start building.

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