Guide · Building regulations
The principal designer role: what homeowners need to know
Since October 2023, building regulations include new duties for everyone involved in building work. Here’s what the principal designer does, when you need one, and how it affects your extension.
Following the Building Safety Act 2022, the Building Regulations in England changed in October 2023. As well as setting standards for buildings, they now set out duties for the people involved in building work, known as dutyholders. Many homeowners haven’t heard of these changes, but they apply to most extension projects.
The dutyholder roles
- The client: the person the work is being done for, which for an extension is usually the homeowner.
- Designers: anyone who prepares or changes the design, such as an architectural designer or structural engineer.
- Contractors: anyone who carries out the building work, including builders and specialist trades.
- The principal designer: the designer who plans, manages and monitors the design work so that it complies with building regulations, and coordinates the other designers.
- The principal contractor: the contractor who does the same for the building work on site.
When is a principal designer needed?
A principal designer and principal contractor are needed where more than one contractor is involved in the project. That covers most extensions, which typically involve a main builder plus electricians, plumbers or other trades.
What if I don’t appoint one?
Domestic clients are treated differently from businesses. If you don’t appoint a principal designer yourself, the role passes to the designer in control of the design phase, and the principal contractor role passes to the contractor in control of the building work. It’s far better for these roles to be agreed clearly at the start than to be assumed, because each role comes with real responsibilities.
Competence
Everyone appointed to a dutyholder role must have the skills, knowledge and experience to carry it out. That’s part of the reason the changes were introduced: to make sure the people designing and building have the competence to get it right.
The CDM principal designer
Separately, the Construction (Design and Management) Regulations 2015 have their own principal designer role, focused on health and safety during construction and in the finished building. It’s triggered in the same way, where more than one contractor is involved. The same person or firm can fill both roles, which keeps things simple.
What it means for your project
- Building Control applications now ask who is acting in these roles.
- At the end of the project, Building Control will normally expect confirmation from the principal designer and principal contractor that, to the best of their knowledge, the work complies.
- Design information needs to be passed clearly to the builder, and any design changes during the build need to be managed and recorded.
How we can help
We act as principal designer under both the Building Regulations and CDM for the extensions we design, so you have one point of contact for the design, the compliance responsibilities and the paperwork. See our building regulations service for more.
This guide gives general information for homes in England and isn’t a substitute for advice on your own property. Rules change, so check the current position before relying on it.
