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

"Do I need planning permission?" and "do I need building regulations approval?" sound like the same question, and homeowners mix them up constantly — but they're two entirely separate systems, assessed by different criteria, and most real renovation projects need to satisfy both, not just one.

Planning permission: is the work allowed at all?

Planning permission (or its exemption, permitted development) is about whether a piece of work is allowed to happen — its size, its impact on neighbours, its effect on the character of the area. It's assessed against local planning policy, not construction standards. See our guide on permitted development for how a lot of smaller residential work can avoid needing a full planning application.

Building regulations: is the work built safely?

Building regulations are about how the work is actually constructed — structural adequacy, fire safety, insulation, ventilation, drainage, electrical safety. They apply regardless of whether planning permission was needed, and cover the technical quality of the build, not its appearance or planning impact. See our full building regulations guide for what's typically covered.

Side by side

• What it asks: planning permission asks "should this be built here, at this size, looking like this?"; building regulations asks "is this actually built safely and to a proper standard?"
• Who assesses it: planning is assessed by your local authority's planning department against local policy; building regulations is assessed by building control (council or private approver) against national technical standards.
• When it's checked: planning permission is a single decision before work starts; building regulations involves inspections at defined stages throughout the build.
• What you get at the end: planning permission is a decision notice; building regulations ends in a completion certificate.
• Can you need one without the other? Yes, in both directions — see the practical examples below.

Practical examples

• A rear extension built within permitted development limits: no planning application needed, but building regulations approval is still required for the structure, insulation, and drainage.
• A loft conversion with a rear dormer: likely permitted development for planning purposes, but definitely needs building regulations sign-off for the new floor structure, fire escape provisions and staircase.
• Replacing windows: usually handled through a competent-person scheme (like FENSA) rather than a separate building control application, but it's still a building-regulations matter, not a planning one, for most homes.
• A change of use with no structural work (for example, converting a garage's use without altering its structure): can sometimes need planning consideration with minimal building regulations implications, though most garage conversions into habitable space do trigger both.

A simple way to decide which applies to your project

• Ask first: "does this change what's allowed to exist here?" — size, position, appearance, use. If yes, check planning permission or permitted development.
• Ask second: "does this involve construction — walls, floors, drainage, electrics, structure?" — if yes, building regulations almost certainly applies, independently of the answer to the first question.
• Most extensions, loft conversions, and structural renovation work will answer "yes" to both.

Both need to be in place before or during the build

Unlike some legal requirements that can be sorted out retrospectively, building regulations approval is meant to be arranged before or as work starts, with inspections at defined stages — not applied for after the work is finished. The same is true for planning permission where it's needed. Sort both out at the planning stage of your project, not once a contractor is already on site.