“Do we need planning or is it just building regs?” is one of the commonest questions I’m asked, and it’s a fair one. Planning permission and building regulations have similar names, both involve the council, and both produce letters full of reference numbers. They do completely different jobs, though, and mixing them up is how people end up with a planning approval they can’t build from, or a finished extension they can’t sell.
The shortest version: planning permission decides whether you can build it. Building regulations decide how it must be built.
What does planning permission cover?
Planning is about the effect of a building on the place around it. A planning officer looks at the size and shape of what you propose, how it sits against the original house, what it looks like from the street, and what it does to the neighbours: their daylight, their privacy, their outlook. They judge it against the council’s local plan and design guidance, which is why the answer can differ between Woking, Guildford and Waverley for very similar houses.
Some work doesn’t need an application, because it falls within permitted development, the national rights that allow certain extensions, loft conversions and outbuildings within set limits. Those rights are narrower in conservation areas and the Surrey Hills, and they can be removed on particular estates or streets. Where you rely on them, a lawful development certificate from the council confirms the work is lawful. Do I need planning permission for an extension? sets out the limits.
A planning permission normally has to be started within three years. It often comes with conditions, some of which, such as approving materials, must be dealt with before work begins.
What do building regulations cover?
Building regulations are national technical standards, set out in a series of approved documents known by letter. The ones that bite on most home projects are structure (Part A), fire safety (Part B), resistance to moisture (Part C), ventilation (Part F), drainage (Part H), stairs and guarding (Part K), energy and insulation (Part L) and electrical safety (Part P). Part L was tightened in June 2022, so new walls, roofs and windows have to perform better than they did even a few years ago.
They apply to almost every extension, loft conversion and structural alteration, whether or not planning permission was needed.
Do I need building regulations approval for an extension?
Almost always, yes. Compliance is checked by building control. You can use the council’s building control service or a registered building control approver, a private alternative. Since April 2024 both work under the Building Safety Regulator, and their inspectors have to be registered.
There are two main routes. A full plans application has the drawings checked and approved before work starts, which is what I recommend for anything structural, because problems are found on paper and not on site. A building notice skips the plan check and relies on inspections as the work goes along.
Either way, an inspector visits at key stages, typically the foundations, the drains, the floor, the roof structure and the finished work. At the end you receive a completion certificate. Keep it. Your buyer’s solicitor will ask for it, and a missing certificate is one of the things that holds up house sales. Work done without approval can sometimes be put right afterwards through a regularisation application, but that can mean opening up finished work for the inspector to see.
Who is responsible for building regulations?
Since October 2023 the regulations name “dutyholders” on building work, homes included. Where more than one contractor is involved, which covers most extensions, there has to be a principal designer and a principal contractor, each responsible for planning and checking that the work complies. On most domestic projects the homeowner’s own duties pass to them automatically. It’s worth knowing who holds those roles on your job before work starts. What is a principal designer? explains it in more detail.
Planning permission and building regulations side by side
| Planning permission | Building regulations | |
|---|---|---|
| The question it answers | Can this be built here? | Is it built safely and properly? |
| Who decides | The council’s planning department | Council building control or a registered approver |
| What they look at | Appearance, size, effect on neighbours and the area | Structure, fire, insulation, ventilation, drainage |
| Always needed? | No, not if it is permitted development | Almost always for building work |
| What you end up with | A decision notice, often with conditions | A completion certificate |
Some everyday examples
Taking out a load-bearing wall inside the house needs no planning permission, but it does need building regulations approval, because a beam and the posts carrying it are structural work.
A single-storey rear extension within permitted development limits needs no planning application, but it needs building regulations approval, and if it’s close to a neighbour’s foundations or on a shared wall, party wall notices too.
A loft conversion is often permitted development, and always needs building regulations approval. The fire escape route and the new staircase are where most of the regulations bite.
Replacement windows usually need no planning permission unless the house is listed or in an area with an Article 4 direction, but they do fall under building regulations, normally handled by the installer through a registered scheme.
A listed building adds a third consent, listed building consent, which is separate from both and applies to internal work as well as external.
Why does the difference matter for your project?
Planning drawings and building regulations drawings are not the same thing. Planning drawings show what the building will look like. They aren’t detailed enough for a builder to price from accurately, or for building control to approve. That’s why the work after planning, the technical drawings, the structural engineer’s calculations and the specification, matters as much as the application itself.
People who stop at the planning approval and ask builders to price from it often get quotes that vary wildly, because each builder is guessing at the parts the drawings don’t show. The differences come back later as extras. Choosing the right builder covers what to ask before you sign.
The order I work in is set out on the our process page: planning route first, then design and the application, then the technical drawings that satisfy building regulations and let builders price the same thing. If you’re unsure which consents your project needs, planning advice and feasibility is where that question gets answered.
One point to finish on, because it’s asked often: starting work without the consents you need is never a shortcut. Councils can take enforcement action under both systems, and unauthorised work tends to surface at the worst moment, usually when you come to sell.
If you’d like to know which approvals your project needs, the free 15-minute Clarity Call is the place to ask.
