The UK government has introduced a law called the Building Safety Act.
While Building Regulations tell us how an extension must be built (e.g., type and thickness of insulation), the Building Safety Act focuses on who is legally responsible for making sure those rules are followed. It applies to all building work in the UK, including your domestic extension.
The law is designed to stop cowboy building practices. It makes compliance a legal requirement, and failing to meet the standards is now treated as a criminal offence.
To ensure the project complies with the law, we are all assigned specific roles. Here is a very basic summary of who does what on a home extension, self-build or other domestic project:
My Role (The Principal Designer) Under the Building Safety Act
As your Principal Designer, I am legally in charge of ensuring the design package, technical drawings and specifications comply with the law before any physical building work starts. Because my role is design-only I do not monitor construction on site and I rely on the builder to notify me of any changes. My job is to:
- Ensure Regulatory compliance: Make sure all architectural drawings, material specifications and notes meet UK Building Regulations.
- Coordinate Specialist input: Review and merge technical data from third-party consultants such as structural engineers calculations and energy assessments into the compliant design package.
- Facilitate Dutyholder Coordination: Work alongside you and the builder to ensure plans are clear, practical and aligned with legal building requirements before construction begins.
- Manage design variations: where the builder requests a design change on site, to review and formally approve this to ensure the project remains legally compliant.
- Information Management: Keep digital records of the approved drawings, documents and calculations and any subsequent design changes which are officially reported to me by the builder during construction and which I have approved as being compliant with building regulations.
- The Principal Contractor’s Role (Your Main Builder)
This is the professional in charge of the physical construction site once work begins. Under the law they take on responsibility for both the on-site health and safety (under the CDM regulations) and physical building compliance (under the Building Safety Act). Their role in relation to the Building Safety Act is:
- Construction Compliance (BSA): Ensure the building work is in accordance with the approved plans and complies with Building Regulations. Ensure the tradespeople they bring to the project are competent to do the work.
- Cooperation (BSA): Work closely with us, alerting us if the design needs to be changed so we can check compliance and approve the change.
- Log the Milestones (BSA): Coordinate with the building inspector for site visits and ensure the correct notices (like start notice and commencement notice) are accurately managed
Note: Day to day health and safety on site falls under separate CDM Regulations 2015, and those legal responsibilities transfer automatically to the Principal Contractor on a domestic project. CDM deals with planning and monitoring the health and safety on site to keep workers and you and your family and the public safe.
The Final Sign-Off (The Declaration)
When the extension is finished, you won’t just automatically get a Building Control Completion Certificate.
Before the council or building inspector can sign off on the project, You, the Principal Designer, and the Principal Contractor must all sign a joint legal declaration. This document states that we have all worked together and guarantee that the extension fully complies with the law.
Further guidance will follow as your project progresses
I will provide further guidance and a checklist to clarify Building Safety Act roles and procedures so you know what to expect before construction starts and how we make sure your project remains compliant during construction.
