Planning Permission vs Building Regulations: What's the Difference?

These two terms get mixed up constantly. Homeowners say "I've got planning" when they mean building regs, or assume that planning permission covers everything. It doesn't. They're separate systems run by different people, checking different things, and you may need both.

Here's the distinction in one sentence:

Planning permission decides what you can build. Building regulations decide how it must be built.

The Quick Comparison

When You Need Planning Permission

You need planning permission when your project changes the external appearance, size, or use of your property beyond what's allowed under permitted development. Common triggers include extensions that exceed the permitted development size limits, changes to the front of a property, building in a conservation area, and converting a house into flats.

The council's planning department assesses whether your proposal is acceptable in terms of its impact on the street, the neighbours, and the local area. They don't care whether your foundations are deep enough or your walls are insulated — that's building regulations territory.

Nationally, 86.7% of planning applications are approved. But this varies enormously by council and ward. Some areas approve over 95% of applications. Others refuse more than one in four.

See what gets approved in your council →

When You Need Building Regulations

Almost always. Building regulations apply to the vast majority of construction work, including projects that don't need planning permission.

A single storey rear extension that falls within permitted development limits? No planning permission needed — but you absolutely need building regulations approval. The building inspector will check your foundations, your damp-proof course, your structural steelwork, your insulation, your electrics, and your drainage.

The only exceptions are truly minor works: like-for-like repairs, small porches, certain small detached outbuildings, and some internal works that don't affect the structure.

The Common Scenarios

Rear extension under permitted development: No planning permission needed. Building regulations required. This is the most common scenario where people get confused — they hear "permitted development" and assume they don't need any approvals at all.

Rear extension exceeding PD limits: Planning permission required. Building regulations also required. Two separate applications to two separate bodies.

Loft conversion: May or may not need planning permission depending on the type (rear dormer vs front dormer, conservation area, etc). Will always need building regulations — particularly for fire escape, structural loading, insulation, and staircase design.

Internal wall removal: No planning permission needed. Building regulations required if it's a structural wall — which it often is, even when it doesn't look like one.

New kitchen or bathroom: No planning permission. Building regulations apply to drainage, electrics, and ventilation changes.

What Happens If You Skip Either

Skipping planning permission is risky. The council can discover unauthorised development years later and issue an enforcement notice requiring you to undo the work. This can happen when you try to sell the property and the buyer's solicitor checks the planning history.

Skipping building regulations is arguably worse. Without a completion certificate from building control, you may struggle to sell your home. Mortgage lenders and conveyancing solicitors look for building regulations sign-off on any work done to a property. The lack of it can delay or derail a sale.

More practically, building regulations exist to keep people safe. An extension with inadequate foundations, insufficient fire escape routes, or dangerous electrics is a genuine hazard.

The Order of Operations

If you need both, get planning permission first. There's no point paying for detailed structural drawings and building regulations submissions if the council refuses your planning application and you need to redesign.

The typical sequence for a project that needs both approvals is: design the extension with your architect, submit for planning permission, wait for the decision (typically 8 weeks), then once approved, develop the detailed construction drawings and submit for building regulations.

Some homeowners submit both simultaneously to save time. This is possible but risky — if planning changes are required, your building regs drawings become out of date.

Before You Spend Anything

The cheapest mistake to avoid is the one you spot before committing money. Before you pay an architect, before you file an application, take 10 seconds to check what your council actually approves.

PlanningLens analyses 2,500,000+ planning decisions — broken down by council, ward, and project type. It won't tell you whether you need building regulations (you almost certainly do). But it will tell you whether your planning application stands a good chance of success, based on what's actually been approved in your area.