Two separate approval systems govern building work, and confusing them causes real problems.
Planning against building control
Whether you may build something against whether it is built safely.
Which are assessed by different processes.
What building regulations cover
Structure, fire safety, insulation, ventilation, drainage and access.
Certificates
Completion documentation required when selling.
Which missing paperwork complicates.
Retrospective approval
Regularising work done without approval.
Which is possible and more difficult.
Why the distinction matters practically
Planning permission asks whether something should exist; building control asks whether it is safe and performs adequately.
Which means work can have planning permission and still be unlawful, or need building control approval with no planning involvement at all.
Most internal work needs building control and no planning, which surprises people who assume permitted development means unregulated.
Common work requiring approval
Structural alterations, electrical work, drainage, heating and insulation.
Which covers a large share of renovation.
Competent person schemes
Registered trades self-certifying their own work.
Which is why some jobs need no separate inspection.
Selling afterwards
Buyers' solicitors asking for certificates.
Which is when missing paperwork becomes a problem.
A general note
Requirements differ substantially by country and region.
Why people get caught out
Work is commissioned, completed and paid for, and only years later when selling does anyone ask for the certificate that was never obtained.
Which turns a routine sale into a delay, an indemnity policy or a retrospective application.
Asking a contractor at the outset who is responsible for building control and what documentation will be provided prevents almost all of this.
Listed and protected buildings
Additional consent regimes with serious consequences for breach.
Which apply to a large number of ordinary homes in older areas.
Neighbour-related requirements
Party wall and boundary procedures.
Which are separate again.
Energy performance
Standards tightening over time.
A general note
Regimes differ substantially by country and even by locality.
Getting it right from the start
Establish before work begins whether approval is needed, who will obtain it, and what documentation you will receive at the end.
Which takes one conversation and prevents the entire category of problems described above.
Building control bodies will answer questions before work starts, and they would generally much rather do that than deal with it afterwards.
Enforcement
Powers to require alteration or removal.
Which are used and are time limited in some jurisdictions.
Insurance implications
Unapproved work potentially affecting cover.
Which is worth checking.
Buying a property with unapproved work
Indemnity insurance and retrospective approval as the usual routes.
Where to check
Local authority building control and national guidance documents.
Why it is worth knowing how these things work
Most of the systems that shape ordinary life are invisible by design. Nobody explains why a parcel took an odd route, why a film left a streaming service, why a wait extended, or why a price changed between two searches.
The absence of explanation is rarely deliberate concealment. It is that the people running these systems are solving their own problems, and the reasoning behind their decisions is obvious to them and completely opaque from outside.
Understanding the mechanism does not always change what you can do about it. It does remove a category of low-grade frustration that comes from assuming something is arbitrary, unfair or aimed at you personally when it is usually none of those things.
The pattern that recurs
Across almost all of these systems, the same three things turn out to be true. The behaviour that looks irrational from outside is optimising for something the observer cannot see. The cost that seems unexplained is usually concentrated in one specific stage of the process. And the information that would resolve the confusion is generally published somewhere and read by nobody.
That last point is the most useful. Regulators, operators and industry bodies publish an enormous amount of explanatory material that answers exactly the questions people complain about not being able to get answers to. It is dry, it is not promoted, and it is free.
A note on sources
Where regulation is involved, national regulators publish the actual rules and they are generally clearer than press coverage of them. Where an industry is involved, trade publications aimed at people working in it are considerably more informative than consumer coverage.
Practices described here vary substantially between countries, and anything with legal, financial or medical consequences warrants checking against the rules that apply where you are.
The pattern that recurs
Across almost all of these systems, the same three things turn out to be true. The behaviour that looks irrational from outside is optimising for something the observer cannot see. The cost that seems unexplained is usually concentrated in one specific stage of the process. And the information that would resolve the confusion is generally published somewhere and read by nobody.
That last point is the most useful. Regulators, operators and industry bodies publish an enormous amount of explanatory material that answers exactly the questions people complain about not being able to get answers to. It is dry, it is not promoted, and it is free.