The Building Safety Act 2022 introduced new dutyholder responsibilities for builders, designers and clients. One of the biggest areas of uncertainty for many builders taking on these new roles is understanding the relationship between the principal designer and principal contractor.
This webinar, delivered in partnership with the Chartered Institute of Architectural Technologists (CIAT), looks at how these roles work together on smaller-scale projects, including extensions, refurbishments and domestic building work.
Drawing on the experience of builders, designers and technical specialists, the discussion focuses on common situations that arise on site and how they should be managed.
What builders need to know
- A principal designer under the Building Regulations is different to the role of principal designer under Construction (Design and Management) Regulations.
- Principal designers and principal contractors have different responsibilities.
- Builders should understand what responsibilities they are accepting before agreeing to act as principal designer.
- Changes to products, specifications or construction details may need to be reviewed before work proceeds.
- If you make a design change without agreement from the principal designer, you may be taking on legal responsibility for that decision.
- Maintaining a ‘Golden Thread’ of digital records – emails, photos, and specs – is now a functional necessity for compliance.
Watch the webinar
Further guidance from the Chartered Institute of Architectural Technologists (CIAT) is available on their website.
In this webinar, we’re talking to CIAT experts about:
- The difference between a principal designer under the Building Regulations and a principal designer under the Building Safety Act.
- Who is responsible for appointing dutyholders.
- How principal designers and principal contractors should work together.
- What happens when designs need to change during construction.
- Documenting decisions and maintaining an evidence trail.
- Common questions from builders about competence, appointments and compliance.
Principal designer and CDM principal designer: what's the difference?
One of the most common areas of confusion following the Building Safety Act reforms is the difference between the principal designer role under the Building Regulations and the principal designer role under the Construction (Design and Management) Regulations 2015 (CDM).
Although the titles are the same, the responsibilities are different.
The Building Regulations principal designer is responsible for planning, managing and monitoring design work so that, if built as designed, the project complies with the Building Regulations.
The CDM principal designer focuses on managing health and safety risks during the pre-construction phase of a project.
On some projects, the same organisation may carry out both roles. However, being appointed as a CDM principal designer does not automatically mean someone is acting as the principal designer under the Building Regulations.
Before work starts, builders should establish who is carrying out each role and ensure appointments are confirmed in writing.
Who is responsible for appointing a principal designer?
For most domestic projects, homeowners will have little knowledge of the dutyholder requirements introduced through the Building Safety Act.
This can create uncertainty about who is responsible for appointing the principal designer and principal contractor.
Where a principal designer is required, they should be appointed before construction work starts. The principal designer must have the competence and control needed to carry out the role.
If you are being asked to take on the principal designer role, it is important to understand exactly what responsibilities you are accepting. The role is not simply an administrative requirement. It includes responsibility for coordinating and monitoring design work to support compliance with the Building Regulations.
During the webinar, AS Homes director Peter Atkins reflected on the importance of recognising the limits of your own competence:
'I'm definitely not qualified to be designing anything. I have a good understanding of how things work and how things go together, but I'm no architect.' Peter Atkins, Director, AS Homes and Construction Limited.
What if the drawings need to change?
It is not unusual for issues to come up once work starts on site.
A specified product may no longer be available. A supplier may suggest an alternative. A detail that looked straightforward on paper may be difficult to build in practice.
Where a change affects the design, it should be discussed with the principal designer before the work goes ahead.
If the principal contractor changes something on site without checking the principal designer first and getting their approval, the principal contractor is essentially taking on the design liability and responsibility for this change.”
During the webinar, one example involved structural timber that was not available in the size shown on the drawings. The contractor proposed an alternative solution, which was reviewed by the principal designer, structural engineer and building control before it was approved.
In another example, a contractor wanted to replace a specified fire-treated cladding system with a cheaper alternative. The principal designer was not prepared to accept responsibility for the revised specification and did not update the drawings. The contractor and client then had to agree a separate route forward with building control.
The examples are different, but they illustrate the same point. A change that seems minor on site can affect compliance with the Building Regulations.
If you need to change something that affects structure, fire safety, insulation, ventilation or another regulated element of the design:
- Speak to the principal designer before proceeding.
- Explain why the change is needed.
- Provide any technical information that supports the proposal.
- Keep copies of emails, revised drawings and product information.
- Record what was installed and where.
Keeping records and evidence
Throughout the webinar, the panel emphasised the importance of maintaining clear project records.
For builders, compliance is not only about carrying out the work correctly. It is also about being able to demonstrate what was built and how decisions were made.
Useful records may include:
- Photographs taken during construction
- Emails relating to design changes
- Revised drawings and specifications
- Product data sheets and technical information
- Correspondence with building control
- Inspection records and site notes
Keeping these records creates a clear history of the project and can provide valuable evidence if questions arise later.
Five actions builders can take now
- Confirm who is acting as principal designer before work starts.
- Make sure appointments and responsibilities are agreed in writing.
- Discuss significant design changes before carrying out the work.
- Keep records of decisions, approvals and product substitutions.
- Do not take on responsibilities that fall outside your competence.
Download a free explainer for your clients
Homeowners are often unaware of their responsibilities as a dutyholder under the BSA. Being ready to help guide them through this is a great opportunity to show your profesionalism and duty of care for your clients, and can help you to avoid disagreements and ambiguity during the project.
FMB members can download a free leaflet to show to clients that explains their dutyholder role in plain English - click below to grab a copy.
Frequently asked questions about dutyholder roles
Does the principal designer need to visit site?
The webinar panel discussed different approaches to site involvement. On some projects, the principal designer may carry out site visits as part of their appointment. On others, their role may focus primarily on the design stage.
What matters is that responsibilities are clearly defined and documented at the outset of the project.
Can a builder act as the principal designer?
Potentially, yes.
However, the principal designer must have the competence, knowledge and control needed to fulfil the role. Builders should carefully consider whether they have the skills and resources required before accepting the appointment.
What happens if I make a design change without consulting the principal designer?
The webinar speakers highlighted that, in practice, a contractor may be taking responsibility for that design decision. This is why communication and documentation are so important when changes are proposed.
Does building control confirm compliance?
Building control plays an important role in assessing compliance with the Building Regulations.
However, responsibility for compliance sits with the dutyholders involved in the project. Builders, designers and other dutyholders should not rely solely on building control to identify issues.
