Principal Designer (CDM 2015) in London

CDM 2015 places duties on those who design and manage construction work. The Principal Designer coordinates health and safety during the pre-construction (design) phase on projects involving more than one contractor — planning, managing and monitoring design-stage health and safety, and ensuring relevant information flows to those who need it. The aim is to design out foreseeable risks before they reach site.

For domestic clients, duties under CDM are often reduced and can pass to the contractor or principal contractor by default, but they do not disappear — they must be allocated clearly. Where appropriate, we can act as Principal Designer under CDM, confirming the role, scope and terms in a written appointment before work begins. We do not assume the role without that appointment, and we are clear where competence or insurance means a separate appointment is more suitable.

The CDM Regulations apply to all construction work, including domestic home projects, whenever more than one contractor is involved. They require a Principal Designer to plan, manage and monitor health and safety during the design phase, the gathering of pre-construction information, and — for larger jobs, broadly those lasting more than thirty working days with significant numbers on site or exceeding five hundred person-days — formal notification to the Health and Safety Executive. The aim is not paperwork for its own sake but making sure safety is considered by the people best placed to influence it: the designers.

The heart of the Principal Designer’s role is to eliminate or reduce foreseeable risks while a project is still on the drawing board, when changing them costs nothing. That means anticipating how the building will actually be constructed and maintained — working at height, the stability of the structure during the build, the disturbance of asbestos in older homes, access for maintenance — and designing to avoid the hazard rather than leaving it to be managed on site. Risks designed out early are the ones that never have to be controlled later.

There are now two separate "Principal Designer" roles and they are routinely confused. This role — the CDM Principal Designer — is about construction health and safety. The other, introduced under the Building Safety Act, is the Principal Designer for building regulations compliance, a different statutory duty concerned with the design meeting the building regulations. The two can be held by the same person or by different people, but they are distinct appointments with distinct responsibilities, and we are explicit about which we are providing on any given project.

The role is about planning, managing and monitoring health and safety in the pre-construction phase: identifying significant risks, coordinating designers, and helping the right information reach the Principal Contractor. It is not the same as contract administration or full site supervision. We explain the boundaries so homeowners do not confuse three different appointments.

Competence and adequate resources are legal expectations. We will not accept a token appointment that cannot be discharged properly.

Home extensions and refurbishments still create real construction risk: structural openings, work at height, asbestos, public highway interfaces. CDM is not only for commercial sites. We help domestic clients understand when formal PD/PC appointments apply and how designer coordination reduces avoidable harm.

Early hazard information — services, structure, access — belongs in design, not as a surprise on site.

Where we are already architect, a Principal Designer role can be a natural extension if scope and fees are explicit. Where another designer leads, we can still contribute design information without holding the PD duty. Clarity on who holds which duty is itself a safety control.

We set this out in appointment documents before construction information is issued.

The trigger for most of these duties is whether more than one contractor is involved, and that threshold is easier to reach than homeowners expect. A single builder who subcontracts the electrics, the roof and the glazing is still one contractor, because those subcontractors work under that builder. The moment the client engages someone directly alongside the builder, a kitchen fitter, a specialist glazier, a waterproofing firm, a licensed asbestos removal contractor, the project involves more than one contractor and both a principal designer and a principal contractor exist. For a domestic client those duties pass by law to the contractor or principal contractor, and the roles default to whoever controls each phase if nobody is formally appointed, so the practical task is confirming in writing who holds them rather than discharging a duty yourself.

Projects also change shape as they go. A job that starts as one builder and a clear scope becomes a multi-contractor project when the client brings in their own joiner, or when a specialist supplier insists on installing its own product. On a basement or a loft conversion the specialist trades are frequently contracted separately from the outset. We look at how the work is actually going to be bought, not only at what the drawings show, and we will say plainly when the duties have already been triggered and nobody has been appointed to hold them. Getting that wrong is not usually deliberate; it is what happens when procurement is decided months after the design was signed off.

Pre-construction information is simply what is already known about the site and the existing building that anyone designing or pricing the work needs in order to do it safely. On a domestic project it is rarely a formal document to begin with. It is the refurbishment and demolition asbestos survey on an older house, the drainage and services information, what the engineer found when a floor was lifted, the position of the incoming gas and electricity supplies, whether the roof can be reached without a scaffold standing on a neighbour's garden, and the constraints of a house that is still lived in.

The usual failure is not that this information is wrong but that it is thin, and the gaps surface only once a contractor is on site and the price has been agreed. Much of the value here lies in saying what is missing, asking for the surveys that would fill it, and being straight that a survey is a cost nobody had budgeted for. The client is also the source of much of it: on an older London house that can mean past building control records and whatever the previous owner left behind. Where we are also producing the building regulations drawings, that information has to stay consistent across both, so it is gathered once and issued to everyone who needs it.

Design-stage work only counts for something if what it produces reaches the people doing the building. The Principal Contractor cannot begin construction without a construction phase plan, and that plan is only as good as the information handed across to write it: the significant risks that could not be designed out, the sequence the temporary and permanent structure depends on, the surveys, and the residual hazards buried in the existing fabric. Handover is a real event with a date and a named recipient, not an email trail that everybody assumes somebody else read, and it is worth recording what was issued and when.

At the other end there is the health and safety file, which is not the same thing as the operation and maintenance manual the contractor puts together. The file is for whoever works on the building next: where asbestos was knowingly left in place and sealed, how the new structure carries load and what must not be cut, how a rooflight or a high window can be reached safely. It is meant to be proportionate, so on a house it should be short and genuinely useful. On domestic projects the file can end up sitting with the contractor, which is the usual reason it cannot be found when the house is later sold or altered. We would rather it lives with the homeowner, filed with the construction stage records.