16 December 2025
Principal Designer for Building Regulations - in Simple Language
A 10 year old’s guide to the Principal Designer for Building Regulations (and just about everything an adult needs to know)
by Hal Jones
The Architect
Architects design buildings, with help from specialists. hey:
lead the design of the building
include all the specialist designs by other people (like steel structures and electrical wiring)
make sure the design follows rules called building regulations
Because there are usually lots of designers on a project, the Architect is often called the Lead Designer.
But Projects Got Complicated!
In modern times, there was a problem, because projects got very complicated!
sometimes it wasn’t clear which designer was responsible for what, which could be dangerous. Imagine if something went wrong - everyone could say “That wasn’t my job.”
There were other problems that made things even more difficult:
the government building rules and guidance could be confusing, missing, or even wrong!
companies that sold building materials and products sometimes did not test things properly to make sure they were safe, and sometimes they sold their products in a way that made it difficult for designers to realise they could be dangerous.
clients (the people that pay for buildings to be built) were often trying to save money by finding cheaper ways of doing things and this led to risk taking short cuts, even when safety could be a worry.
A Big Disaster
After a big disaster, a fire in a tall building, there was a lot of sadness and anger that such a thing could happen. There were investigations and it was found that thousands of other tall buildings also had worrying problems that needed to be fixed to make them fire safe.
Following a long review, it was clear there were lots of different types of problem that needed fixing, but one of the things that the Government did was to say:
“There must always be someone officially in charge of making sure the design follows the rules, especially the safety rules, no matter how complicated the project is.”
So, the new rules are like what an architect traditionally does, but the government wanted to make the responsibility a LAW, not a choice. But the law couldn’t name the architect as responsible, because sometimes an engineer is in charge, like when a type of factory needs to be designed, for example.
The government decided that the new name for the person (or company) responsible is ‘Principal Designer’. Just like an architect, some of the important things a Principal Designer needs to do are:
understand the project building type, design and construction process
understand the main design rules and risks (things that are dangerous or can go wrong), to make sure the finished building is safe and does not break the law
understand the design activities, the types of specialist and who needs to do what and when.
to talk to clients, to make sure their clients know what they need to do, including to get all the smart people they need in the team, and to make sure there is enough time for everyone to do their jobs carefully, so the building can be designed safely.
to make sure everyone is working well together, talking and giving each other drawings to check. Imagine a group of friends building something in Lego – if they are in separate rooms and they don’t talk, what they are doing will not fit together very well.
This is a bit strange:
The law does not need the Principal Designer to design anything!
Imagine it’s like the Principal Designer might not play with the Lego, but they must choose their best Lego friends and make sure they are in the same room and talking to each other and that they agree what they are building and who is doing what so that the pieces fit together nicely and it doesn’t all collapse.
In the real grown-up world, Principal Designers rely on designs and evidence from specialists, but they must be smart and sceptical. If something goes wrong, the question becomes: “Did they set up a good system — and did they challenge things when they should have?”
Confusing bits (yes, even grown-ups argue about this):
The Principal Designer is often a company, not one person, but if it is a company, then the company must say who the person is that will do the job (it does not even say that person must be employed within the company, so some people say that it could be someone from another company).
The law does not say what type of person or company should do the job of the Principal Designer. So, there is often disagreement about who can do the job best.
A lot of people think that when the Architect (or lead designer) is already very involved in the whole design, they should take the responsibility of being the Principal Designer. They have more chance of spotting something that does not seem right.
Other people argue that a separate person is better, like a second pair of eyes, checking the design process. They might spot something that the lead designer has missed.
Sometimes the Client likes to give the builder the responsibility to do the design work - these contracts are called 'design and build'. Builders don't usually like taking responsibility for design work, but with the new rules, the Client usually says they must, otherwise the Builder doesn't get a chance to do the job.
Whoever is the Principal Designer, they must be competent. Competency is a word that the new rules use to describe whether someone can do the job properly. There is a company called the British Standards Institute that thought a lot about how to explain competency and they wrote a long report. This was worrying for Clients, because Clients are responsible for choosing all the people they need for the project and many Clients thought they needed to score everyone using the new competency ideas which took them a long time. But really the Client only needs to be sensible, like to choose a company that has already designed the types of building they want to build. If they want to use a company that they do not know anything about, or that has not done the same type of building before, then the Client can ask more questions and do more checks to make sure they are good enough to do the job.
It is not completely clear how much checking (the law calls it monitoring) of the design the Principal Designer needs to do, but most people agree that it is not the Principal Designer’s job to check that the design details follow the rules. The Principal Designer can’t be specialist in everything, but must have enough experience to spot areas that look more dangerous and to be able to make sure the designers are dealing with those areas carefully.
Some people think that the Principal Designer needs to check and confirm that the builder is building everything properly, but that is wrong! The Principal Designer only has responsibilities for the design. For complicated jobs it is good for the client to be paying a specialist person to be checking things on the construction site. That person is called a 'clerk of works'. The government didn't make this role a law, but maybe they will in future!