Building Regulations vs Planning Permission: Two Systems, Both Required

Planning permission is about whether your project is acceptable in principle. Your local council assesses:

• Size and position — is the extension too large, too tall, or too close to a boundary?
• Appearance — does the design fit with the existing house and the local area?
• Impact on neighbours — will it block light, overlook gardens, or cause noise issues?
• Policy compliance — does it follow the council’s local plan and national planning policy?

If your project falls within permitted development rights, you do not need to apply for planning permission. The government has already decided that projects meeting certain size and design limits are acceptable without individual approval.

You can get formal proof that your project is permitted development by applying for a Lawful Development Certificate. This costs £274 and gives you a legal document confirming your project did not need planning permission — useful when you come to sell.

Who enforces it: Your local planning authority (the council’s planning department).

What happens if you skip it: The council can issue an enforcement notice requiring you to undo the work, alter it, or apply retrospectively. Enforcement action can be taken within 4 years for building work.

Building regulations are about safety and performance. They set minimum standards for how your project is designed and constructed. The key areas they cover are:

• Structure (Part A) — foundations, walls, beams, and load-bearing elements must be strong enough to support the building safely
• Fire safety (Part B) — escape routes, fire doors, fire-resistant materials, smoke alarms, and access for fire services
• Moisture and weather protection (Part C) — damp-proofing, drainage, and resistance to weather penetration
• Insulation and energy efficiency (Part L) — walls, roofs, floors, and windows must meet thermal performance standards. This is one of the most common areas where projects fail
• Ventilation (Part F) — adequate airflow for habitable rooms, kitchens, and bathrooms
• Electrical safety (Part P) — new circuits, consumer unit changes, and work in bathrooms and kitchens must be certified
• Drainage and waste (Part H) — foul and surface water drainage must be properly connected
• Glazing safety (Part K) — glass in doors, low-level windows, and areas near stairs must be safety glass
• Access (Part M) — reasonable provision for people to access and use the building

Building regulations apply to almost all structural building work regardless of whether you needed planning permission.

Who enforces it: Either your local authority building control team or a private approved inspector. You choose which one to use.

What happens if you skip it: You will not receive a completion certificate. This causes problems when selling — your buyer’s solicitor will ask for it. You may need to apply for retrospective regularisation, which typically costs 150% of the original fee and may require opening up completed work for inspection.

Planning permission asks: “Should this be built here?”

Building regulations ask: “Is this being built safely?”

Planning permission and building regulations are applied for separately, assessed separately, and charged separately.

You can submit both applications at the same time. You do not need planning permission before applying for building regulations, or vice versa.

Building Notice — you notify building control that you are starting work. There are no plans to approve upfront — the inspector checks compliance during construction through site inspections. Best for: straightforward domestic projects like simple extensions, where you and your builder are confident the design complies. Faster to start, but you carry the risk of getting something wrong and having to redo it.

Full Plans — you submit detailed plans and the building control body checks them before work starts. You receive a formal plans approval confirming your design complies. Best for: larger or more complex projects, loft conversions, and anything where you want certainty before breaking ground. Takes longer to get started, but gives you confidence that the design is right.

You can also choose between your local authority’s building control team and a private approved inspector. Both have the same legal authority. Private inspectors may be faster but often charge more. Your local authority building control team may offer free initial consultations.

If you have never had building work done before, the inspection process can feel daunting. Here is what to expect:

Your builder (or you) must notify building control at key stages so an inspector can visit. The typical inspection stages for a rear extension are:

1. Commencement — notify before work starts
2. Foundations — inspector checks the excavation before concrete is poured
3. Damp-proof course — checked before walls go up
4. Drainage — pipes and connections inspected before covering
5. Structural steels — if applicable, checked before covering
6. Pre-plaster / insulation — inspector checks insulation values and fire stopping before walls are plastered. This is one of the most important inspections
7. Completion — final inspection covering everything from ventilation to electrics

After the final inspection, building control issues a completion certificate. Keep this safe — your buyer’s solicitor will ask for it when you sell.

“I got planning permission, so I’m covered.” No. Planning permission does not mean your project complies with building regulations. You still need separate building regulations approval and inspections.

“It’s permitted development, so I don’t need building regs.” Almost always wrong. Permitted development removes the need for planning permission only. Most PD projects still need building regulations approval. The exceptions are small outbuildings, porches, and some other minor works.

“My builder said he’d sort all the approvals.” Check. Many builders handle the building control notification, but some do not. Make sure you know who has applied and that a completion certificate has been issued when the work is finished.

“I didn’t get a completion certificate but the work was done years ago.” You can apply for regularisation — retrospective building regulations approval. Your local authority building control team will inspect the work (which may mean opening up walls or floors) and charge a fee, typically 150% of what the original application would have cost.

The fastest way to check whether your project needs planning permission is to use our free PD checker. Answer a few questions about your project and property, and you will get a rule-by-rule assessment against the relevant GPDO class.

For building regulations, contact your local authority building control team or a private approved inspector. Describe your project and they will tell you whether building regulations approval is needed and which route (Building Notice or Full Plans) is appropriate. Many offer a free initial phone consultation.

If you want formal proof that your project is permitted development, our Permitted Development Certificate Report gives you everything you need to apply for a Lawful Development Certificate — including a full PD assessment, constraints check, and application checklist tailored to your address.