CDM 2015 on a commercial re-roof: what the client must do
Updated 23 October 2026 · SEO Dons Editorial
Check your re-roof against the rules ↓
Does CDM 2015 apply to a roof repair or a re-roof?
Usually yes. The Regulations count the renovation, repair and maintenance of a structure as construction work, and a client is any person for whom a project is carried out. HSE describes a commercial client as any individual or organisation that has a construction project carried out as part of a business, and says the client duties apply in full. A landlord letting a warehouse, a school trust and a retailer with a flat roof all qualify.
HSE also says CDM 2015 does not apply to all maintenance work, so an edge case is worth raising with a competent adviser. For the repair-or-replace choice itself, see the repair or replace decision guide; this page covers what the law asks of the client once the work is commissioned.
What must the client do on every roof project?
Whatever the size of the job, regulation 4 asks the client to do the following.
- Make suitable arrangements for managing the project, including enough time and other resources, so that the work can be done without risks to health or safety so far as is reasonably practicable. The arrangements must be maintained and reviewed throughout.
- Appoint people who can do the work. Whoever appoints a designer or contractor must take reasonable steps to satisfy themselves that the appointee has the skills, knowledge, experience and, for a firm, the organisational capability.
- Provide pre-construction information as soon as practicable to every designer and contractor appointed or being considered. For a roof that could include earlier survey reports, any asbestos information and the position of fragile rooflights; the pre-construction information guide goes through it.
- Make sure a construction phase plan is drawn up before the construction phase begins, by the contractor on a single-contractor job or by the principal contractor otherwise. See the construction phase plan guide.
- Keep watch. Where a principal designer is appointed, ensure a health and safety file is prepared, and take reasonable steps to check that the principal designer and principal contractor perform their own duties.
When must a principal designer and principal contractor be appointed?
Whenever more than one contractor is working on the project, or it is reasonably foreseeable that more than one will be at any time. The client appoints both in writing, as soon as practicable and in any event before the construction phase begins. HSE counts sub-contractors as contractors, so a roofing firm working alongside a scaffolder, an electrician isolating rooftop plant or an asbestos contractor has already crossed the line.
The principal designer is a designer who takes control of the pre-construction phase, and design includes specifications, so whoever writes the re-roof specification is a designer. HSE's FAQ says a client can take the role itself, and that one organisation can hold several roles, provided it has the skills, knowledge, experience and capability for each. If the client appoints nobody, the client carries the duties of the missing role.
England's Building Regulations also have a principal designer and principal contractor, with a different purpose, in force from 1 October 2023. The Building Safety Act guide explains the difference.
When does a roof project need an F10 notification?
When the work is scheduled to last longer than 30 working days with more than 20 workers on site at once, or to exceed 500 person days. The tests are alternatives, and the first needs both conditions. HSE's FAQ says every day on which construction work is likely to be carried out counts, weekends and holidays included.
| Test | Threshold in regulation 6(1) | Worth checking |
|---|---|---|
| Duration and peak workforce | Longer than 30 working days and more than 20 workers at the same time at any point | Both conditions must be met |
| Total effort | More than 500 person days | Add up every contractor's scheduled worker days |
The client must notify HSE in writing as soon as practicable before the construction phase begins, display the notice in the site office and update it if necessary. HSE no longer accepts paper, email or postal notifications, so the form goes through HSE's online F10 page. It needs the contact details of the client, principal designer and principal contractor, and carries a declaration that the client knows its duties. The client may ask someone else to submit it. On a notifiable single-contractor job, the sole contractor is entered as both principal designer and principal contractor.
How do the duties differ on a patch repair and a phased re-roof?
Two hypothetical examples show where the lines fall. Neither describes a real project.
Example A: one contractor, a small repair
For example, a retail unit's flat roof leaks at one outlet and the owner instructs one roofing contractor to replace a small area of membrane over two days with two operatives. With one contractor, no principal designer or principal contractor is appointed. The client must still make suitable arrangements, pass on the relevant pre-construction information and make sure a construction phase plan exists, which on a single-contractor job is the contractor's task. At about four person days, there is no F10.
Example B: several trades, a phased strip-and-recover
For example, a 6,000 m² warehouse roof is renewed in three phases while the building stays in use. A roofing contractor strips and re-covers, a scaffold contractor builds access and edge protection, an electrical contractor isolates rooftop plant, and an asbestos contractor removes cement sheets from one bay. With four contractors, the client appoints a principal designer and principal contractor in writing before the construction phase begins, and the principal contractor owns the construction phase plan.
Suppose the programme shows 40 working days with a peak of 14 people. The first F10 test fails, because 14 is below 21. But if 14 people work on each of the 40 days, that is 560 person days, so the second test is met and the client must notify. A long programme with a modest crew can be notifiable.
| Question | Example A | Example B |
|---|---|---|
| Contractors | One | Four |
| Principal designer and principal contractor | Not appointed | Appointed in writing |
| Construction phase plan | Contractor | Principal contractor |
| F10 to HSE | No | Yes, if the schedule exceeds 500 person days |
Is the client liable if a contractor is hurt on the roof?
That depends on which duty was or was not met, because CDM 2015 spreads duties across several people. The client's duties are those above. Contractors have their own duty to plan, manage and monitor their work so that, so far as is reasonably practicable, it is carried out without risks to health and safety. HSE says a commercial client is accountable for the effect its decisions have on health, safety and welfare on the project. A separate guide covers liability when a contractor is injured on your roof; this page is not legal advice.
What are the client's duties after the roof is finished?
At the end of the project the principal designer, or the principal contractor where there is no principal designer, passes the health and safety file to the client. The file holds information likely to be needed during any later project, so it belongs with the roof's other records. The client must keep it available for anyone who needs it and, on disposing of its interest in the structure, hand it to the new owner. HSE adds that the client's responsibility for health and safety in the use and maintenance of the building continues until then. If you want to talk a roof project through, you can send an enquiry through the form on this site.
Sources
- The Construction (Design and Management) Regulations 2015, regulations 2, 4, 5, 6, 8, 12 and 15 and Schedule 1, legislation.gov.uk, checked 22 October 2026
- HSE: Commercial clients, Are you a commercial client?, CDM 2015 FAQ, Contractors, Principal designers, checked 22 October 2026
- HSE: F10 notification of construction project and L153, Managing health and safety in construction, checked 22 October 2026
- Building Regulations etc. (Amendment) (England) Regulations 2023, regulation 1, legislation.gov.uk, checked 22 October 2026
Common questions
Does a one-contractor roof repair need a principal designer?
No. A principal designer and principal contractor are needed only where more than one contractor is, or is reasonably foreseeable to be, working on the project. The client’s other duties still apply, and the single contractor must draw up the construction phase plan before setting up the site.
Can the building owner act as principal designer?
HSE says a client can take the role itself, provided it has the skills, knowledge, experience and, for an organisation, the organisational capability to carry out every function of a principal designer. A client that appoints nobody carries those duties anyway.
Who submits the F10, and what does it need?
The duty to notify is the client’s, although the client may ask someone else to submit it. The online form needs the contact details of the client, principal designer and principal contractor, and HSE issues a serial number for later edits.
What if the landlord and the tenant both commission the roof work?
Where there is more than one client, one or more may agree in writing to be treated as the only client. Some information duties stay with every client, so the agreement should say who holds the roof records and survey reports.
Related guides
Check your re-roof against the rules
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