CDM, the F10 and the Building Safety Act: where the rules stand in 2026

No. Regulation 6 of the Construction (Design and Management) Regulations 2015 is as it was made. A project is notifiable if the construction work is likely to last longer than 30 working days and have more than 20 workers working simultaneously at any point, or is likely to exceed 500 person days. The client notifies, as soon as is practicable before the construction phase begins, and a construction phase plan is required on every project whether or not it is notified.

The rumour that it changed usually comes from two places. One is memory of CDM 2007, under which duration alone triggered notification at 30 days, and which the 2015 regulations replaced with the two-condition first limb. The other is the Building Safety Act, which added a second set of dutyholders with the same names as CDM’s and is read as a change to CDM. It is not. CDM 2015 is a health and safety regulation made under the Health and Safety at Work Act; the new dutyholders are in the Building Regulations, made under the Building Act.

Northern Ireland runs the same thresholds under its own instrument. The Construction (Design and Management) Regulations (Northern Ireland) 2016 have been in operation since 1 August 2016, and regulation 6 notifies the Health and Safety Executive for Northern Ireland on the same two limbs.

The first F10 limb needs both conditions. Thirty-five working days with six operatives on site is not notifiable on it.

Part 2A of the Building Regulations 2010, inserted by the Building Regulations etc. (Amendment) (England) Regulations 2023 and in force since 1 October 2023. It gives every building project in England a client, designers and contractors with duties under the Building Regulations, and where more than one contractor is or will be working on the project, a principal designer and a principal contractor appointed by the client in writing before the construction phase begins. It also sets competence requirements for each of them.

The names are CDM 2015’s and the appointments are not. A firm appointed principal contractor under CDM has not, by that act, been appointed principal contractor under the Building Regulations. The client has to make both appointments, and can make them to different people. On a domestic extension with a builder and an electrician the builder is very likely to be both, and still has to be appointed as both, in writing.

• CDM 2015 asks whether the work is safe to build. Part 2A asks whether it complies with the Building Regulations. The same person can hold both duties and the duties are different.
• Both regimes turn on the same trigger: more than one contractor on the project.
• Both appointments have to be in writing, and neither is made by the other.

NoteThe trap is a contract that appoints “the Principal Contractor” once, in capitals, and means CDM. A subcontract written before October 2023 and reused since may still do exactly that.

Section 65 of the Building Safety Act 2022 defines a higher-risk building as one in England that is at least 18 metres in height or has at least 7 storeys, and contains at least 2 residential units. For the design and construction phase the description also takes in care homes and hospitals that meet the height or storey condition.

Since 1 October 2023 the Building (Higher-Risk Buildings Procedures) (England) Regulations 2023 have routed the design and construction of those buildings through the Building Safety Regulator rather than a local authority or an approved inspector. The regulator’s building control approval is needed before the work starts, and its completion certificate before the building is occupied. Those are the two stages the industry calls gateways two and three.

The regime applies in England. Wales has legislated separately: the Building Safety (Wales) Act 2026 sets three categories of multi-occupied residential building, Category 1 at least 18 metres or 7 storeys, Category 2 at least 11 metres or 5 storeys but below Category 1, and Category 3 below that, for the occupation phase. Scotland routes all building work through a building warrant from the verifier and a completion certificate under the Building (Scotland) Act 2003, and Northern Ireland through the Building Regulations (Northern Ireland) 2012.

1. 01Count the person days as well as the workers. A long job with a small crew is where the 500-person-day limb catches people, and it is the limb nobody checks.
2. 02On any project in England with more than one contractor, get both principal appointments in writing: CDM 2015 and Building Regulations Part 2A. One letter naming both regimes is enough. One letter naming one is not.
3. 03Write a construction phase plan for every job, notifiable or not. One or two pages for a small job, specific to the site.
4. 04If the building is at or near 18 metres or 7 storeys and has two or more homes in it, stop and check whether it is higher-risk before anything is submitted anywhere, because the building control body is a different one.
5. 05Keep the health and safety file for the client at the end. Under the higher-risk regime the golden thread of building information is a separate obligation from it.

A CDM project record against the job: whether the project is notifiable, the principal designer and principal contractor by name and company, the estimated duration and the maximum number of workers on site, the pre-construction information, the construction phase plan and the health and safety file. Beside it, an F10 record holds the particulars a notification needs, the client, the site address, the principals, the construction phase start, the expected duration and the maximum workers, and whether it has been submitted.

The Health & Safety module around it holds versioned RAMS signed per operative, site inductions, toolbox talks with a signed attendance list, permits to work and near-miss reporting, and can gate QR site clock-on on induction, CSCS card and a signed current RAMS. It is included from Solo.

NoteWhat it does not do. Estimark does not submit the F10 to HSE; you submit it on HSE’s own service and record that you did. It prepares nothing for the Building Safety Regulator and holds no golden thread. And it has no separate record for a Building Regulations Part 2A appointment: it holds the CDM one, and where both apply the second is a document you keep. See RAMS and site safety in Estimark.