Do I need building regulations approval as well as planning permission?

The short answer

Yes, almost certainly. Planning permission and building regulations approval are separate consents, decided by different people against different tests, and needing one has no bearing on whether you need the other. You can need both, either, or in rare cases neither.

The confusion is understandable, because both are administered by your council and both involve submitting drawings. They are not the same process and they do not talk to each other.

What each one actually controls

Planning permission is about whether you should be allowed to build what you are proposing, in that place. It considers the effect on the appearance of your property and the street, the impact on neighbours in terms of light, privacy and outlook, and whether the proposal accords with local policy. It is a judgement about acceptability.

Building regulations are about how the thing is built. They are technical standards covering structural stability, fire safety, thermal performance, ventilation, drainage and electrical safety. There is no discretion involved: either the construction meets the standard or it does not.

So a scheme can be entirely acceptable in planning terms and still fail building control, and a scheme that needs no planning permission at all still has to satisfy every applicable technical standard.

Permitted development does not mean no approval

This is where most homeowners come unstuck. Permitted development is a planning concept. It means the works do not require a planning application. It says nothing whatsoever about building regulations, which apply on their own terms.

A single-storey rear extension built entirely within permitted development limits still requires foundations designed for the ground conditions, insulation meeting current thermal standards, a structural opening properly supported, drainage connected correctly, and adequate ventilation and means of escape. All of that is building control territory.

Who grants it, and how

Building regulations approval comes from building control, which is either your local authority's building control team or a private approved inspector. Both are legitimate routes and both issue a completion certificate at the end.

There are two ways in. A full plans application submits the technical drawings and calculations for approval before work starts, which is the safer route and the one we recommend on anything structurally involved. A building notice starts work with less paperwork and relies on inspection as you go, which suits small, simple jobs but leaves you exposed if an inspector disagrees with something already built.

Either way, the process runs on staged inspections rather than a single decision: foundations before they are covered, damp proof course, structural elements, insulation before it is closed up, drainage before backfilling, and a final inspection.

The completion certificate is the thing that matters

At the end of a compliant project, building control issues a completion certificate. That document is what a buyer's solicitor will ask for.

Its absence is one of the more common causes of trouble at sale. It cannot be conjured retrospectively with any ease, because the inspector cannot certify work they never saw. A regularisation application is possible but often requires opening up finished work to prove what is behind it, which is expensive and destructive.

The practical consequence is that skipping building control does not save money. It defers a cost to the least convenient possible moment, when you have a buyer and a chain.

What else runs alongside

Two further processes are separate again, and neither is optional where it applies.

The Party Wall etc. Act 1996 applies where you build on or near a shared boundary or excavate close to a neighbouring structure. On a London terrace or semi this is almost guaranteed. It requires notice, and usually a surveyor.

A build over agreement is required where the extension sits over or near a public sewer, which is common on London plots. That is granted by the water authority, on their timescale, and is worth establishing early rather than discovering mid-build.

The sequence that avoids trouble

Establish the planning route first, because it determines what you are allowed to build. Design to that. Then develop the technical package for building control, which is where the structure, insulation and drainage are resolved properly rather than improvised on site.

Party wall notices and any build over agreement should be running in parallel, not after. They have their own notice periods, and a project held up by a process nobody started is the most avoidable delay there is.