A Principal Designer (PD) is the designer you, as the client, are lawfully obliged to appoint. The PD plans, manages, monitors and co-ordinates the separate design work and outputs of other designers. On smaller projects the PD is often also one of those designers.
Your obligation to appoint a PD applies to construction of all buildings. Including extensions to private homes and new houses. But the obligation does not apply if only one tradesperson is being employed (so its a one-off repair, for example).
Both the CDM Regulations and Building Regulations require a PD appointment. So, in practice, one person, or organisation, usually covers the requirements of both types of Regulations.
On a project to extend your home, if you do not appointment a PD, then the designer you appoint will automatically become the PD. (And the builder you employ automatically becomes the Principal Contactor). Both PD and PC have no choice but to accept their roles. And carry out their duties in them.
So you need a PD to proceed lawfully. In practice you also need a PD for the final sign-off process in connection with Building Regulations. When the building is finished, and before you occupy it, you should obtain a Completion Certificate (CC) from the building inspector. It confirms that the building is built compliant with building regulations.
Issue of the CC by the building inspector depends on two key factors. Firstly, on their satisfactory inspections at certain stages during construction. Secondly, on their receipt of a Notice of Completion (NC).
This NC is your own confirmation that the work complies with building regulations. The NC must be signed by you the client, the Principal Contractor (your builder) and the PD. Read more about all this here.
So if there’s no Principal Designer to sign the Notice of Completion you can’t get the Completion Certificate. Meaning the completion process remains undone. This is a problem if a buyer’s solicitor searches for the Completion Certificate but there isn’t one. And its existence is often a requirement of mortgage funders and insurers.
