Homeowners planning an extension, loft conversion or barn conversion often hear "planning" and "building regs" used almost interchangeably — and assume that getting one means they're covered. They're not the same thing. They're two separate approvals, handled by different people, answering different questions.
Getting this straight early saves money, and it avoids the unpleasant discovery halfway through a project that you've cleared one hurdle but not the other.
The simple distinction
- Planning permission asks: should this be built here at all? It's about land use, appearance, and the effect on neighbours and the surrounding area.
- Building regulations ask: will it be built properly? They set minimum standards for the construction itself — safety, structure, energy efficiency, and health.
You can think of planning as the "what and where," and building regulations as the "how."
What planning permission looks at
When a council considers a planning application, it's weighing things like:
- The size, height and design of the proposal, and how it sits with the existing house and street
- The impact on neighbours — loss of light, overlooking, or an overbearing structure
- Materials and appearance, particularly in sensitive areas such as conservation areas
- Access, parking and drainage effects
- Local and national planning policy
The output is a decision: granted (usually with conditions), or refused.
What building regulations look at
Building regulations are a set of technical requirements covering how the work is constructed. Typical areas include:
- Structure — foundations, beams, walls and floors able to carry their loads (this is where structural calculations come in)
- Fire safety — escape routes, fire resistance, and detection
- Insulation and energy efficiency — thermal performance of walls, roofs, floors and windows
- Ventilation and moisture — preventing damp and condensation
- Drainage — how waste water and rainwater are handled
- Electrical safety and accessibility
Compliance is checked by inspection during construction, and signed off with a completion certificate at the end.
Who handles each
- Planning is always decided by your local planning authority — the council.
- Building control can be handled by the council's building control team or, in England, by a registered private building control approver. You choose which route to use.
When do you need each one?
| Situation | Planning permission | Building regulations |
|---|---|---|
| Single-storey rear extension within permitted development limits | Usually not | Yes |
| Extension that exceeds permitted development limits | Yes | Yes |
| Loft conversion | Sometimes (many fall under permitted development) | Yes |
| Internal structural alterations, such as removing a load-bearing wall | Usually not | Yes |
| Barn conversion | Usually yes | Yes |
| Some small detached garden buildings | Often not | Sometimes not |
The important row is the first one. "No planning permission needed" does not mean "no approval needed." An extension built under permitted development still has to meet building regulations — and building control can ask you to put things right if it doesn't.
Common mix-ups
"We got planning permission, so we're fine to start." Planning permission doesn't approve the construction details. You'll still need building regulations approval, and most of the technical drawings and specifications that building control wants are prepared after planning is granted.
"It's permitted development, so there's nothing to submit." Building regulations still apply. Work done without them can cause problems later — particularly at sale, when a buyer's solicitor will ask for a completion certificate.
"Building control will tell me if the design is wrong." Building control checks compliance against the regulations, not whether the design suits your needs, and they won't produce your drawings or calculations for you.
The two submissions, step by step
For a typical extension that needs planning permission, the sequence looks like this:
- Design and planning drawings are prepared, and the planning application is submitted
- The council decides — householder applications are normally determined within eight weeks
- Technical drawings and structural calculations are prepared in detail
- Building regulations is submitted — either as a full plans application, or via a building notice for simpler work
- Inspections take place at key stages during construction (foundations, drainage, structure, and so on)
- A completion certificate is issued when the work is signed off
If your project falls under permitted development, steps 1 and 2 may fall away, but the rest still apply.
Why it helps to have both handled together
The two systems feed into each other. A design that looks great on a planning drawing still has to be buildable — and meet the structural, fire and insulation requirements — once it reaches building control. Spotting those conflicts before planning is submitted, rather than after, avoids redesign and wasted fees.
That's one of the practical advantages of having design, planning and structural engineering handled in the same practice. If you'd like to talk through what your project will need, get in touch, or see how a project typically runs on our process page.