Work out whether your project is notifiable, who has to be appointed in writing, and which documents the law actually requires — then build the information you need for the F10.
What this tool is. A planning aid that applies the tests in CDM 2015 to the answers you give. It is only as good as those answers — particularly the programme figures, which are estimates until the job is built. It is not a substitute for a competent CDM adviser, and it is general guidance rather than legal advice. Nothing you enter leaves your browser.
Coming back to an assessment? Paste your saved code
If you saved a code last time, paste it here and everything you entered will come back — the programme figures, the client and contractor answers, the Schedule 3 selections and the F10 details. If this is your first visit, ignore this and start at step 1 below.
STEP 1
Where is the work, and is it construction work?
CDM applies to construction projects of every size. There is no exemption for small jobs, short jobs or work on someone’s house. The first question is simply which set of regulations applies to you.
Which country is the site in?
Is the work “construction work” as CDM defines it?
The definition is broad. It covers building, civil engineering and engineering construction work, and specifically includes alteration, conversion, fitting out, commissioning, renovation, repair, upkeep, redecoration, other maintenance, de-commissioning, demolition and dismantling of a structure. It also covers site preparation and clearance, assembly or disassembly of prefabricated elements on site, removal of a structure or demolition waste, and the installation, commissioning, maintenance, repair or removal of services normally fixed within or to a structure — mechanical, electrical, gas, compressed air, hydraulic, telecoms and similar.
Two things the definition deliberately leaves out
Site survey work is excluded, as are pre-construction archaeological investigations. So is exploration for or extraction of mineral resources, and preparatory activities at a place where that extraction happens. Cleaning only counts as construction work where it involves water or an abrasive at high pressure, or corrosive or toxic substances.
STEP 2
Client and contractors
Almost everything else in CDM follows from two facts: what kind of client you are, and whether there is more than one contractor. Get these two right and the rest of the tool falls into place.
What kind of client is this?
Has the domestic client made a written agreement with the principal designer?
A domestic client can agree in writing with their designer that the principal designer will carry out the client duties, rather than those duties passing automatically to the contractor or principal contractor. It has to be in writing.
How many contractors will work on the project?
A contractor is anyone who, in the course or furtherance of a business, carries out, manages or controls construction work. Count every business on the job, not just the main one. A builder plus a separate electrician is two contractors. A builder who sub-contracts the electrics is still two contractors. If it is reasonably foreseeable that more than one contractor will be involved at any time, answer “more than one” now rather than later.
Who is the enforcing authority for this site?
For nearly all projects this is HSE. A small number of sites are notified elsewhere instead.
STEP 3
Is the project notifiable?
Regulation 6 sets two tests. A project is notifiable if the construction work on site is scheduled to last longer than 30 working days and have more than 20 workers working simultaneously at any point in the project, or to exceed 500 person days. The tests are independent — meeting either one makes the project notifiable.
A working day is any day on which construction work takes place
Every day construction work is likely to happen counts, including weekends and bank holidays if the site is working, and including days where the work is short. It is not the same as a business day, and it is not the length of the contract.
Test 1 — duration and peak headcount
Test 2 — person days
A person day is one worker working for one day. Build it up phase by phase if the crew size changes across the job, which it nearly always does. If you already have a total from a programme or tender, enter it directly instead.
No phases entered yet.
Result
Notification tests
—Working days
—Peak workers
—Person days
Not yet testedStatus
STEP 4
Who must be appointed, and who does what
Generated from your answers in steps 1 to 3. Regulation references are to CDM 2015 unless the tool has been set to Northern Ireland, where the equivalent provisions of CDM (NI) 2016 are numbered the same way.
Notification changes nothing except notification
This is the single most common misunderstanding about CDM. Whether a project is notifiable has no bearing on whether you need a principal designer, a principal contractor, a construction phase plan or a health and safety file. Those follow from the number of contractors. A three-day job with two contractors needs written appointments and a construction phase plan; a notifiable job with one contractor needs neither appointment. The requirements of CDM apply whether or not the project is notifiable.
Appointments and roles
Answer the questions in steps 1 to 3 and the duty holder map will appear here.
Documents this project requires
Document
Required?
Who prepares it
Reg
Answer steps 1 to 3 first.
Work involving particular risks
Where any of these apply, the construction phase plan must include specific measures for them. This is Schedule 3 of the Regulations. Tick everything the project involves.
Planning demolition or refurbishment of a building built before 2000? The duty to manage asbestos and the survey position need settling before the pre-construction information goes out. Our asbestos register and management plan tool covers that side.
STEP 5
Information for the F10
Schedule 1 of CDM 2015 lists exactly what a notification has to contain. These are those particulars. Fill them in here, then copy them across to the online form — this tool does not and cannot submit anything on your behalf.
Site and project
Programme
This is a separate particular from the planned duration, and deliberately so. The regulations ask what the client allowed, not only what the programme says. Where the two differ, that difference is worth a conversation before work starts.
Client
Principal designer
Principal contractor
Appointments already made
The declaration
The last particular in Schedule 1 is a declaration, signed by or on behalf of the client, that the client is aware of the client duties under the Regulations. On the online form this is a step you complete yourself. It is not a formality — a client who signs it without knowing what the duties are has just put that in writing.
SIGN OFF
Who is making this determination?
These appear on the printed determination. A determination with a name and a role against it carries considerably more weight than an anonymous one, and if anybody later asks who decided a project was not notifiable, this is the answer.
Work through steps 1 to 5 and the summary will build itself here.
Keep a copy
The determination above is what gets filed. Print it or save it as a PDF and keep it with the project records — being able to show why you concluded a project was or was not notifiable is worth as much as the conclusion itself. Only the determination prints; the questions used to build it do not.
SAVE
Save this assessment
Copy the code below and keep it with the project records. Pasting it back into the box at the top of the Scope tab restores everything you entered here. Nothing is stored on our servers and nothing is stored in your browser — if you lose the code, the assessment is gone.
What CDM 2015 actually requires
The Construction (Design and Management) Regulations 2015 came into force on 6 April 2015 and apply to every construction project in Great Britain. Northern Ireland has its own near-identical version, the Construction (Design and Management) Regulations (Northern Ireland) 2016, which came into force on 1 August 2016. There is no lower size threshold in either. A day replacing a shopfront is a construction project; so is a two-year hospital build. What changes with scale is how much you have to do, not whether the Regulations apply.
The framework rests on a small number of decisions made early. The client makes suitable arrangements for managing the project, including allocating enough time and resource. Designers eliminate what risk they can at the drawing board and pass on information about what they could not eliminate. Contractors plan, manage and monitor the work they control. Where more than one contractor is involved, two coordinating roles appear — a principal designer for the pre-construction phase and a principal contractor for the construction phase — and the client must appoint both, in writing.
Why “more than one contractor” is the question that matters
Under the 2007 Regulations, the appointment of coordinating roles was tied to whether a project was notifiable. CDM 2015 broke that link deliberately. Appointments now hang on the number of contractors, and notification hangs on size. The two questions are answered separately and one does not imply the other.
This catches people out in both directions. A short domestic extension with a builder and a separate electrician is a more-than-one-contractor project: it needs a principal designer, a principal contractor, written appointments and a construction phase plan, even though it will never come close to being notifiable. A large single-contractor refurbishment might be notifiable and still need no principal designer at all.
The construction phase plan is not optional on any project
Every project needs one. On a project with more than one contractor the principal contractor draws it up, during the pre-construction phase and before the site is set up. On a single-contractor project the contractor draws it up, as soon as practicable before setting up the site. In both cases it must set out the health and safety arrangements and site rules, and include specific measures for any work falling within the particular risks listed in Schedule 3.
The health and safety file is different. That one is genuinely conditional: it is only required on projects involving more than one contractor, it is prepared by the principal designer, and it is handed to the client at the end so that whoever does the next job on that building knows what they are walking into.
Two roles called “principal designer”
Since 1 October 2023 there have been two entirely separate duty holder roles in England sharing the name principal designer, and confusing them is now one of the more expensive mistakes available on a project.
The CDM principal designer is appointed under regulation 5 of CDM 2015. The role is about health and safety: planning, managing, monitoring and coordinating health and safety during the pre-construction phase, making sure designers comply with their duties, helping the client pull together the pre-construction information, and preparing the health and safety file. It applies across Great Britain, on every project with more than one contractor, domestic or commercial.
The Building Regulations principal designer was created by the Building Safety Act 2022 and introduced through Part 2A of the Building Regulations 2010 in England, by amendments in force from 1 October 2023 with a transition period that ended on 6 April 2024. That role is about compliance with the Building Regulations — technical standards, not health and safety — and it applies to work requiring a building regulations application.
They are appointed by the same person, they may well be the same firm, and one appointment does not discharge the other. This tool deals only with the CDM role. If your project needs building control sign-off in England, treat the Building Regulations appointment as a separate exercise.
The Building Regulations side is a separate body of law with its own duty holders, competence expectations and compliance statements, and CDM training does not cover it. If the distinction is new to you, Building Safety Act 2022 Awareness (E-learning) covers the regime the second principal designer role comes from.
Common questions
Does a notifiable project need a principal designer and principal contractor?
Not because it is notifiable. Those appointments are required where there is more than one contractor, or where it is reasonably foreseeable there will be. A notifiable single-contractor project needs neither. HSE’s own guidance on completing the F10 acknowledges this and tells you to enter the sole contractor’s name in both the principal designer and principal contractor fields, then explain in the free text box that it is a single-contractor project.
Who actually submits the F10?
For a commercial client, the client. The duty sits with them and cannot be contracted away, although they may ask someone else to submit it on their behalf. For a domestic client, the duty transfers: it is carried out by the contractor on a single-contractor project, by the principal contractor where there is more than one, or by the principal designer where there is a written agreement that the principal designer will carry out the client duties.
What if the project becomes notifiable partway through?
Notify as soon as possible. If a project was not notifiable at the outset but the scope changes so that it now meets one of the tests, the duty to notify bites at that point. The notice itself also has to be periodically updated if necessary, and updates should make clear that they relate to an earlier notification. Programmes slipping past 30 days or crews growing past 20 are the usual triggers, which is why it is worth re-running the test when the programme changes rather than filing the original answer and forgetting it.
How exact are the thresholds?
Exact. The wording is “longer than 30 working days”, “more than 20 workers” and “exceed 500 person days”. Thirty working days is not longer than 30. Twenty workers is not more than 20. Five hundred person days does not exceed 500. In practice, sitting exactly on a threshold is a sign your estimate is not precise enough to rely on, and most people in that position notify.
Who counts as a domestic client?
Someone having construction work done on their own home, or the home of a family member, where it is not done in connection with a business. Landlords, housing associations, charities, local authorities and other businesses that happen to own domestic property are not domestic clients. Neither is someone having work done on a business attached to their home, such as a shop.
Does the F10 have to be displayed on site?
Yes. The notice must be clearly displayed in the construction site office, in a comprehensible form, where any worker engaged in the construction work can read it, and it must be kept up to date. The client can do this themselves or ask the principal contractor or contractor to do it.
What happens if the client does not make the appointments?
For a commercial client, the duties land on them. If they fail to appoint a principal designer they must carry out the principal designer duties themselves; if they fail to appoint a principal contractor they must carry out the principal contractor duties. For a domestic client the mechanism is different and automatic: the designer in control of the pre-construction phase becomes the principal designer, and the contractor in control of the construction phase becomes the principal contractor, whether or not anyone intended that.
Is this tool free?
Yes. No signup, no email, no account. Everything runs in your browser and nothing you enter is sent to us. Copy the save code or print the summary to keep a record.
Training that goes with this
CDM duties fall on people who mostly did not ask for them — clients who commission one project a decade, designers who did not think of themselves as duty holders, contractors picking up client duties on domestic work. Envico lists CDM awareness, principal designer and site management courses from independent accredited providers, online and in the classroom.
If the project also needs building control sign-off in England, the Building Regulations duty holder regime sits alongside CDM rather than inside it, and is examined separately.
Checked against the Regulations and HSE published guidance on 29 July 2026. The following were verified on that date against the statutory text on legislation.gov.uk and HSE’s own guidance:
The regulation 6(1) notification tests, in their exact statutory wording, including that both limbs of the first test must be met and that the second test stands alone.
The regulation 2(1) definition of “working day” as any day on which construction work takes place, and HSE’s guidance that every such day counts, including weekends and bank holidays.
The regulation 5 trigger for appointing a principal designer and principal contractor — more than one contractor, or reasonable foreseeability of more than one — and the consequences under regulation 5(3) and 5(4) where a commercial client fails to appoint.
The regulation 7 transfer of domestic client duties, including the automatic operation of regulation 7(2) and the disapplication of regulation 5(3) and (4) by regulation 7(3).
That the construction phase plan is required on every project, under regulation 12(1) where there is more than one contractor and regulation 15(5) where there is only one.
That the health and safety file is required only on projects involving more than one contractor, confirmed both by regulation 12(5) and expressly in HSE’s guidance.
The fifteen particulars in Schedule 1, the welfare requirements in Schedule 2 and the ten categories of particular risk in Schedule 3.
The alternative enforcing authorities under regulation 6(4) and 6(5) — the Office of Rail and Road, and the Office for Nuclear Regulation.
HSE’s current F10 guidance, including who must notify, that paper and email notifications are no longer accepted, and the instruction on completing the form for single-contractor projects.
The existence and separate legal basis of the Building Regulations principal designer role in England from 1 October 2023.
Sources.The Construction (Design and Management) Regulations 2015 (SI 2015/51) and The Construction (Design and Management) Regulations (Northern Ireland) 2016 (SR 2016/146), both on legislation.gov.uk; Managing health and safety in construction: Construction (Design and Management) Regulations 2015, Guidance on Regulations (L153, HSE, 2015); and HSE’s F10 notification form guidance.
This tool applies the two notification tests to figures you supply. It cannot check whether those figures are realistic, and programme estimates on construction projects are routinely wrong in the direction that matters. It does not assess whether anyone appointed has the skills, knowledge, experience or organisational capability that regulation 8 requires, and it does not tell you whether your construction phase plan or health and safety file is adequate — only whether one is required.
It also treats the Northern Ireland setting as applying the same tests and the same duty structure to a different enforcing authority. That is correct on the points this tool covers, but if you are working in Northern Ireland you should read CDM (NI) 2016 and HSENI’s guidance directly rather than relying on a Great Britain tool with a switch on it.
Guidance changes
This verification describes the position on the date shown above, not necessarily today. Regulations and guidance are revised from time to time. If that date is more than twelve months old, check the current position before relying on anything here. Envico does not undertake to notify users when guidance changes.
