"Main contractor" is a commercial term from the building contract. "Principal contractor" and "principal designer" are legal roles under the Construction (Design and Management) Regulations 2015 (CDM 2015), and the client must appoint them in writing whenever more than one contractor will work on the project. The main contractor is very often appointed as principal contractor, but the contract title does not make it so. The written appointment does.
The same firm can hold more than one of them. Here is what each one means, and how to check you have them right.
What is a main contractor?
The main contractor is the firm that holds the main building contract with the client and usually lets packages of work to subcontractors. CDM 2015 does not use the term at all.
Under CDM 2015, the main contractor and every subcontractor are simply "contractors". Regulation 2 defines a contractor as anyone who, in the course or furtherance of a business, carries out, manages or controls construction work. A non-domestic client doing its own work can be a contractor too.
What is a principal contractor?
The principal contractor is a CDM 2015 role. Under Regulation 5, where there is more than one contractor, or it is reasonably foreseeable that more than one will work on the project at any time, the client must appoint a contractor as principal contractor, in writing. The appointment must be made as soon as is practicable and in any event before the construction phase begins.
The principal contractor's duties are in Regulations 12 to 14. In short, the principal contractor must:
draw up the construction phase plan, or arrange for it to be drawn up, before the construction site is set up (Regulation 12(1))
plan, manage and monitor the construction phase and coordinate health and safety matters, so that work is carried out, so far as is reasonably practicable, without risks to health or safety (Regulation 13(1))
organise cooperation between contractors and coordinate how they meet their health and safety legal requirements (Regulation 13(3))
provide a suitable site induction, prevent unauthorised access and provide welfare facilities (Regulation 13(4))
consult and engage with workers (Regulation 14)
We go through each of these in what does a principal contractor do under CDM 2015? Those duties stay with the principal contractor even when the work is done by others. We explain why in the principal contractor cannot delegate its liability.
What is a principal designer?
The principal designer is the other appointment the client must make under Regulation 5 on a project with more than one contractor. It must be "a designer with control over the pre-construction phase". So it cannot be anyone the client chooses: it has to be a designer, and it has to have control over that phase.
The principal designer's duties are in Regulations 11 and 12. It must plan, manage and monitor the pre-construction phase and coordinate health and safety matters during it. It must ensure all designers comply with their duties, help the client provide pre-construction information, and liaise with the principal contractor. It must help the principal contractor prepare the construction phase plan, and it prepares the health and safety file. The role is often appointed late or to the wrong firm: see the principal designer, the most misappointed role.
Can one firm be more than one?
Yes. HSE's guidance on CDM 2015 (L153) says organisations or individuals can be "one or more dutyholder for a project". Common examples:
The main contractor is appointed principal contractor, and is also a contractor for its own work.
A design and build contractor is principal contractor and a designer, and it may be appointed principal designer if it has control over the pre-construction phase.
A client that fails to appoint either role must carry out that role's duties itself (Regulation 5(3) and (4)). For a domestic client, Regulation 7 instead treats the designer and contractor in control of each phase as the principal designer and principal contractor.
Where there is only one contractor, no principal contractor is appointed. That contractor draws up the construction phase plan itself, under Regulation 15(5). If you are not sure who holds the role on your job, read no principal contractor appointed? The duties fall to you.
What about the building regulations principal designer and principal contractor?
In England, since 1 October 2023, the Building Regulations 2010 have their own principal designer and principal contractor. They were added by the Building Regulations etc. (Amendment) (England) Regulations 2023.
The trigger looks familiar. Under the new Regulation 11D, where there is more than one contractor, or it is reasonably foreseeable that there will be, the client must appoint in writing a designer with control over the design work as principal designer, and a contractor with control over the building work as principal contractor. The duties are different, though. Under Regulations 11M and 11N they are about planning, managing, monitoring and coordinating the work so that it complies with building regulations requirements, not about health and safety.
The client may certify in writing that its CDM principal designer and CDM principal contractor are treated as appointed to the building regulations roles too (Regulation 11D(2)). Where the same firms hold both, that saves a second appointment. It is still two sets of duties, under two sets of regulations, and both need to be covered.
A quick check for your next project
Count the contractors. More than one, now or foreseeably, means a principal designer and a principal contractor are needed.
Read the appointments. Each should be in writing and name the CDM 2015 role. A building contract that calls a firm "main contractor" is not a principal contractor appointment.
Check the principal designer. It must be a designer with control over the pre-construction phase, not just an adviser.
Check the timing. Both appointments must be made before the construction phase begins, and as soon as is practicable.
In England, check the building regulations roles. Either separate appointments, or a written certificate under Regulation 11D(2).
Where one firm holds several roles, make sure it knows which duties come with each one.
Next in this series: who writes the construction phase plan, and when must it be ready?
Where Clarity PC fits
Clarity PC is our system for principal contractors: one connected platform that runs the whole principal contractor role, from F10 notification and the construction phase plan, through live daily site controls, to a complete health and safety file at handover. It is coming soon.
This article is general information, not legal advice.