CDM Regulations apply to construction work in Great Britain. They are not limited to major developments, high-rise buildings or large contractor-led projects. If construction work is being planned, designed, managed or carried out, the Construction (Design and Management) Regulations 2015 may create duties for the client, designers, contractors and project team. The practical question is not only whether a project is large enough to be notified to HSE. The real question is whether construction work is being carried out and whether risks must be planned, managed and monitored before and during the work.
Quick answer: CDM Regulations apply to construction work in Great Britain, including new build, refurbishment, demolition, repair, maintenance, alteration, site preparation and temporary works. A project only becomes notifiable to HSE if it passes the notification threshold, but CDM duties can apply even when the project is not notifiable.
When Do CDM Regulations Apply?
CDM Regulations apply when construction work is carried out. This includes more than traditional building work. It can include alteration, conversion, fitting out, commissioning, renovation, repair, upkeep, redecoration, maintenance, demolition, dismantling and site preparation connected with construction activity.
This matters because many project teams only think about CDM when a site is large, fenced, crane-served or formally run by a principal contractor. In reality, CDM can apply to a short-duration package, an intrusive investigation, a temporary support operation, a roof repair, a concrete breakout or a structural alteration inside an existing building. The scale of the work changes the level of management needed, but it does not remove the basic duty to plan and control risk. A small project can still involve serious risks if the structure is unknown, access is poor, services are live, temporary works are required or the work affects other people nearby.
Notifiable Does Not Mean Applicable
One of the most common CDM mistakes is confusing “notifiable” with “applicable”. A construction project does not have to be notifiable to fall under CDM. Notification is only one administrative requirement for larger projects. CDM duties can still apply below the notification threshold.
A project is normally notifiable to HSE when the construction work is expected to last longer than 30 working days and have more than 20 workers working at the same time at any point, or when the work is expected to exceed 500 person-days. That threshold does not mean smaller works are outside CDM. It means the project may not need F10 notification. The legal duties around planning, management, competence, coordination, welfare and risk control can still remain.
| Project Situation | Does CDM Apply? | Key Point |
|---|---|---|
| Small repair or maintenance job | Usually yes | The work must still be planned and managed safely. |
| Project with more than one contractor | Yes | Principal designer and principal contractor appointments may be required. |
| Project exceeding the notification threshold | Yes | The project must also be notified to HSE. |
| Domestic work carried out by contractors | Usually yes | Domestic client duties are normally transferred to other dutyholders. |
| Temporary works for access, support or stability | Yes | Temporary works must be planned, designed, checked and controlled. |
For a simple definition of CDM itself, see CDM Meaning in Construction: What CDM Stands For and Why It Matters.
Does CDM Apply to Small Construction Jobs?
Yes, CDM can apply to small construction jobs. The misconception comes from treating CDM as something only associated with big projects, large welfare setups or formal HSE notification. In practice, small works can still expose workers, occupants and the public to significant risk.
A short job may involve work at height, asbestos risk, live services, structural alteration, temporary propping, confined access, lifting operations or dust-generating activities. These risks do not become less important because the programme is short. For small projects, CDM should be proportionate. That means the level of paperwork and coordination should match the work. It does not mean ignoring appointments, planning, welfare, risk information or contractor competence.
When Is a Principal Designer or Principal Contractor Required?
Where more than one contractor is involved, CDM normally requires the appointment of a principal designer and principal contractor. This is because risk needs to be coordinated across design decisions, site sequencing, access, welfare, temporary works and contractor interfaces. The principal designer focuses on planning, managing and coordinating health and safety in the pre-construction phase. The principal contractor focuses on planning, managing, monitoring and coordinating the construction phase.
This distinction matters because many construction failures sit between design and site delivery. A risk can be created by a design assumption, missed survey, unclear sequence or late change, but only become visible when the contractor is already on site. The wider CDM dutyholder framework is explained in CDM Regulations Explained: What Construction Professionals Need to Know in 2026.
When Does a Construction Phase Plan Need to Exist?
A construction phase plan should be prepared before the construction phase begins. It should set out the health and safety arrangements, site rules and specific measures needed to control significant risks during the work. For a larger project, the plan may be detailed and supported by method statements, logistics drawings, temporary works procedures, emergency arrangements, inductions and inspection records. For smaller works, the plan can be simpler, but it still needs to reflect the real work being carried out.
The key test is whether someone reading the plan can understand how the work will be managed safely. A generic document that does not address the actual site, sequence, access, structure, services or people affected by the work is weak CDM evidence.
CDM and Temporary Works Interfaces
CDM often becomes most important where temporary works are involved. Propping, falsework, formwork, scaffolding, excavation support, temporary access, crane bases and hoarding can all affect stability, access and public protection. In these cases, CDM asks whether the work has been planned and coordinated. BS 5975 then provides the recognised temporary works procedure for design briefs, design checks, registers, permits, inspections and controlled loading or use.
A temporary works item does not become safe because it is temporary. It becomes safe because it is designed, checked, installed, inspected, controlled and removed under a clear process. The relationship between CDM planning and temporary works control is explained in Temporary Works BS 5975 Process Explained: Full System from Design Brief to Inspection.
Practical Example: Short Works That Still Need CDM Thinking
Consider a small structural investigation inside an occupied building. The works may only take one day and involve a small team. However, the activity may include drilling, breakout, scanning, dust control, exclusion zones, noise, vibration, access restrictions and reinstatement.
CDM thinking would ask whether the client has provided relevant information, whether the contractor understands the structure and services, whether occupants are protected, whether the method is suitable, whether supervision is clear and whether the work has been coordinated with the building’s normal operation. That is why CDM should not be judged only by project size. It should be judged by the work, the risk, the number of parties involved and the consequences if the activity is poorly planned.
Evidence-Based Summary
CDM Regulations apply when construction work is being carried out, not only when a project is large enough to be notified to HSE. While many project teams treat notification as the trigger for CDM, the real trigger is the existence of construction work that must be planned, managed and monitored. The safest interpretation is to treat CDM as a proportionate management framework that applies from small works through to complex multi-contractor projects, with the level of evidence increasing as risk, complexity and interfaces increase.
FAQ: When CDM Regulations Apply
Do CDM Regulations apply to all construction projects?
CDM Regulations can apply to construction work of many sizes and types. The duties should be applied proportionately depending on the nature, risk and complexity of the work.
Does a project have to be notifiable for CDM to apply?
No. Notification and CDM applicability are different issues. A project may be below the HSE notification threshold but still require CDM planning, management and coordination.
When is a project notifiable to HSE under CDM?
A project is normally notifiable if construction work will last longer than 30 working days and have more than 20 workers working at the same time at any point, or if the work exceeds 500 person-days.
Does CDM apply to maintenance work?
Yes, CDM can apply to maintenance work where the activity falls within construction work. The level of planning should be proportionate to the risks involved.
Does CDM apply to temporary works?
Yes. Temporary works such as propping, scaffolding, excavation support, formwork, falsework and temporary access can fall within CDM because they affect construction risk, sequencing and site control.
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Expert Verification & Authorship: Mihai Chelmus
Founder, London Construction Magazine | Construction Testing & Investigation Specialist |
