Health and safety is rarely the first thing people think about when planning a self-build. Most would rather focus on things like layouts, kitchens and wow-factor spaces, or in other words, all the fun stuff.
However, every self-build is a construction project, and the Construction (Design and Management) Regulations, normally shortened to CDM, provide the framework for managing its risks.
A common misconception is that CDM only applies to major commercial developments, not smaller-scale projects. In fact, it does not. In Great Britain, CDM 2015 applies to construction work on projects of every size, including extensions, renovations and new self-build homes. Northern Ireland has similar requirements under separate regulations, which is why every self-builder or home renovator really needs to understand what's involved.
What exactly is CDM?
CDM stands for the Construction (Design and Management) Regulations. Its purpose is to make health, safety and welfare part of how a project is planned, designed and built, rather than something considered only after work starts.
It is about identifying foreseeable risks early, removing them where possible and controlling those that remain. These include falls from height, excavations, temporary structures, moving plant, dust, asbestos, noise and hazardous materials.
CDM is not simply paperwork. Generic risk assessments will not make an unsafe site safe. Designers, contractors and specialist trades must communicate, plan the work and reduce risk in a way that is proportionate to the project.
Why does it matter?
A first-time self-builder is not expected to become a health and safety expert. You do, however, need a competent team, clear responsibilities and sensible arrangements.
Through working on over 660 projects of all shapes and sizes, I know first-hand how important CDM is on a project. Ignoring health and safety on your site could lead to serious injury and you facing a criminal prosecution.
A self-build may involve ground workers, scaffolders, frame installers, roofers, electricians and plumbers, sometimes working in overlapping phases. The self-builder may also buy materials, arrange deliveries and agree changes directly with trades.
When responsibilities are unclear, gaps appear. One contractor may assume another is providing edge protection, or a design change may be agreed without considering structural stability or how it will be built.
Good CDM management provides a structure for sharing information between all parties, coordinating design and controlling construction.
Poorly planned work is more likely to be stopped, redone or delayed, so getting it right also protects the programme and self-build costs.
Who is in charge of CDM on a build?
Someone having work carried out on their own home, or a family member’s home, for reasons unconnected with a business, is normally a domestic client. Because most homeowners lack construction expertise, their CDM client duties normally pass to the contractor where there is only one, or to the principal contractor where more than one contractor is involved.
Most self-builds are multiple-contractor projects. A groundworker, builder, electrician and plumber count as several contractors, even if they are not all on site together.
Two coordinating roles are therefore important:
1. The principal designer
The principal designer (PD) plans, manages, monitors and coordinates health and safety during the pre-construction phase. This is often the architect or another experienced designer, but they must be a designer, control the design process and be competent for the role.
They consider how design decisions affect those who will construct, maintain, alter and eventually demolish the building.
Foreseeable risks should be removed where possible and those remaining clearly communicated. Do not presume that your architect (or designer) is fulfilling the role of PD; this is a separate role, it will be chargeable and should have its own agreement.
Make sure that your principal designer has the required experience and Professional Indemnity insurance to carry out the role.
2. The principal contractor
The principal contractor plans, manages, monitors and coordinates health and safety during construction. This is normally the main contractor or whoever genuinely controls the site.
Their duties include coordinating trades, maintaining the construction phase plan, providing inductions and welfare, controlling access and supervising the work.
Appointments should be clear and set down in writing. Do not assume your architect is the principal designer because they produced drawings, or that the largest trade is automatically the principal contractor.
Confirm who is performing each role and for how long. A domestic client can agree in writing that the principal designer will take on the domestic client duties. Without that agreement, those transferred duties normally sit with the principal contractor.
You can choose to go on a HSE-approved training course if you plan to take on the role yourself. However, I would strongly suggest against this as the risk to you is far too great.
Key CDM requirements
Start with the provision of pre-construction information. The team needs relevant information about the site and proposed work. This may include surveys, existing drawings, underground service information, asbestos surveys, ground investigations, access restrictions and known hazards.
Provide it early enough to influence design, pricing and programme. Discovering asbestos, services or unstable ground after work starts is usually more disruptive and expensive.
You should also expect to cover all of the below:
1. Appoint suitable people
Designers and contractors should have the skills, knowledge, experience and organisational capability appropriate to the project. Ask whether they have completed similar work, how they manage health and safety, who will supervise the site and how higher-risk activities will be planned. You should make reasonable enquiries and allow enough time and money for the work to be carried out safely.
2. Allow adequate time and resources
Scaffolding, temporary works, welfare, safe access and competent supervision all require time and money. A cheaper quotation that overlooks these items is not necessarily a saving. Check what has been included before appointing the contractor.
3. Prepare a construction phase plan
There must be a construction phase plan before construction begins. The principal contractor prepares it on a multiple-contractor project; the sole contractor prepares it where only one contractor is involved.
It should cover responsibilities, site rules, security, welfare, deliveries, emergencies, work at height, excavations, temporary works and other project-specific risks.
It need not be lengthy, but it must relate to the actual project rather than being a generic document with the address changed.
4. Provide welfare from the start
Suitable welfare must be available when work begins. Workers need toilets, washing facilities, drinking water and somewhere to rest. Changing or drying facilities may also be required. Domestic sites are not exempt.
5. Create a health and safety file
Projects involving more than one contractor require a health and safety file, prepared by the principal designer and developed as the project progresses.
Unlike the construction phase plan, it contains information needed to safely use, maintain, alter or demolish the building. This can include hidden services, structural principles, unusual methods, hazardous materials, maintenance access and significant residual risks.
At completion, it should be updated with any amendments to drawings or specification, handed to you and kept with the building records.
How it works during a project
During design, appoint the principal designer in writing, provide the information you hold and identify missing surveys or investigations.
Before appointing a contractor, ask how they will manage the build and whether they are competent to act as principal contractor. Their tender should allow for scaffolding, temporary works, security, welfare and supervision.
Before work starts, confirm that:
- The principal designer and principal contractor have been appointed
- The construction phase plan is in place
- Welfare and site security are ready
- Surveys and design information have been shared
- Significant design risks have been communicated
- Responsibility for temporary works and specialist design is clear
CDM continues throughout the build. Designs change, trades arrive and risks emerge, so the dutyholders must continue communicating and review the plan when circumstances change.
Your role is not to inspect every scaffold or approve every method statement. It is to appoint the right people, understand who is responsible and avoid undermining safe arrangements through unrealistic deadlines or unplanned instructions.
Notifying the Health and Safety Executive
In Great Britain, a project is notifiable to the Health and Safety Executive if it is expected to last longer than 30 working days and have more than 20 workers on site at the same time at any point, or exceed 500 person-days of construction work.
On a domestic project, notification is normally dealt with by the contractor or principal contractor, or by the principal designer where they have agreed to take on the client duties. It is made using an F10 form.
Notification is only an administrative requirement. However, a small, non-notifiable project still needs appropriate planning and a construction phase plan.
It is worth noting that CDM applies whether or not a project is notifiable.
CDM and Building Regulations
For projects in England, changes introduced following the Building Safety Act created a separate Building Regulations dutyholder regime. It uses the same titles – client, principal designer and principal contractor – but the responsibilities are different.
Under CDM, the roles focus on health and safety. Under the Building Regulations, the structure is the focus: the principal designer coordinates compliant design and the principal contractor coordinates compliant construction.
The same person or organisation can perform both versions of a role, but this must be confirmed in writing and they must be competent for each. An architect appointed as the CDM principal designer is not automatically appointed as the Building Regulations principal designer.
For a domestic project in England, the client must provide relevant information, cooperate and allow enough time and resources. Where there are several designers or contractors, the client can appoint the Building Regulations principal designer and principal contractor. If they do not, the designer controlling the design and the contractor controlling the building work take on those roles.
At completion, a notice must normally be given to building control within five days. The client confirms that the work is complete and, to the best of their knowledge, complies with the Building Regulations.
The principal designer and principal contractor confirm that they have fulfilled their duties. Building control cannot issue the completion certificate without the required notice and declarations.
Building control inspections remain an important part of the process, but they do not replace the responsibilities of the client, designers and contractors to deliver compliant work.
What happens when things go wrong?
The worst outcome on site is an accident or long-term damage to someone’s health, or even death. Common causes include poorly planned work at height, excavations, structural alterations, lifting and uncontrolled dust.
The HSE can investigate and take enforcement action, including improvement notices, prohibition notices stopping dangerous work and prosecution. A serious incident can also cause delay, legal costs, penalties and insurance problems.
Although many CDM duties transfer from a domestic client, that is not a reason to ignore the subject. Problems often begin in cases where appointments are unclear, the main contractor does not genuinely control the site or the self-builder coordinates separate trades without a competent principal contractor.
Anyone intending to manage the build or accept a formal dutyholder role should obtain competent advice. Do not accept a title simply as a name on a form.
6 common CDM myths debunked
- Myth: CDM only applies to large commercial sites.
False: CDM applies to construction work of all sizes, including self-builds, renovations and extensions. - Myth: Small projects won’t need a construction phase plan.
False: Every construction project needs one, although its detail should be proportionate. - Myth: If the project is not notifiable, CDM does not apply.
False: The thresholds only determine whether an F10 must be submitted to the Health and Safety Executive. - Myth: My architect is automatically the principal designer.
True and false: The principal designer must control the relevant phase and be clearly appointed. The CDM and Building Regulations roles are also separate appointments. - Myth: The main builder deals with everything.
False: The principal contractor normally carries the domestic client’s transferred CDM duties, but you should still make reasonable enquiries and ensure responsibilities are clear. - Myth: CDM is mainly paperwork.
False: The real test is what happens on site: safe access, competent people, supervision, welfare and coordination.
Final tips
CDM can sound intimidating, but its principles are straightforward and sensible: appoint capable people, define who is in control, share information, allow enough time and money, plan before work begins and keep communicating.
Before construction starts, you should be able to answer the following questions:
- Who is my CDM principal designer?
- Who is my CDM principal contractor?
- Has a construction phase plan been prepared?
- Who holds the Building Regulations roles in England?
- Who will produce the health and safety file?
- Who will sign the completion declarations?
If those answers are clear, CDM and the Building Regulations dutyholder requirements should sit quietly in the background as part of a well-managed project. If they are not, be sure to resolve them before anyone starts digging foundations or erecting scaffolding.
It is far easier, and much less expensive, to establish responsibility at the outset than to discover after something has gone wrong that everyone thought somebody else was in charge. From experience, HSE do not accept a client’s assumption that someone else was responsible!
Understanding these requirements is essential when undertaking a project, even more so if you are considering managing a self-build yourself.
