Planning Permission vs Building Regulations: What's the Difference?
Planning permission and Building Regulations are two completely separate legal systems. Many homeowners confuse them or assume one covers the other. You may need both, one, or neither — but they serve different purposes and are assessed by different teams.
The details
What planning permission covers
Planning permission controls HOW your extension affects the area — its size, position, appearance, and impact on neighbours and the streetscene. It is assessed by planning officers against local and national policy. You may not need planning permission if Permitted Development applies.
What Building Regulations cover
Building Regulations control HOW your extension is built — structural safety, fire safety, insulation, ventilation, drainage, and accessibility. They are assessed by building control officers (council or private approved inspectors). Building Regulations almost always apply to extensions, regardless of planning status.
Can I skip one?
You may skip planning (if PD applies) but you almost never skip Building Regulations. The only common exemptions from Building Regs are: conservatories thermally separated from the house, very small outbuildings (under 15m²), and some like-for-like repairs. Any extension that creates new habitable space needs Building Regulations approval.
| Factor | Planning Permission | Building Regulations |
|---|---|---|
| What it controls | Design, position, size, impact | Structural safety, insulation, fire, drainage |
| Who assesses it? | Planning officer | Building control officer |
| Can you skip it? | Yes (if PD applies) | Almost never |
| Cost (council fee) | Set nationally, revised each year | £200–£900 |
| Cost (professional) | £1,500–£5,000 | £399–£1,500 |
| Timeline | 6–10 weeks | Ongoing during build |
| What you receive | Decision notice | Completion certificate |
Our verdict
You need to think about both systems separately. Planning permission comes first (or a PD check). Building Regulations approval is needed before construction starts. We handle both, priced after a free project review.
Common questions
Frequently asked questions
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