Change a detail on site, and CDM 2015 can make you the designer of that change. Not the architect, not the engineer: you.
It happens on every job. The specified lintel is on a twelve-week lead time, so a heavier steel goes in. The bracket will not fit, so the fixing changes. The gang says a detail cannot be built as drawn, so it is simplified. Most of these changes are sensible. Very few are recorded as what the law says they are: design.
What CDM 2015 says a designer is
Regulation 2 of the Construction (Design and Management) Regulations 2015 defines a designer as any person, including a client or contractor, who in the course or furtherance of a business prepares or modifies a design, or arranges for or instructs any person under their control to do so.
"Design" is defined widely too. It includes drawings, design details, specifications and bills of quantities relating to a structure, and calculations prepared for the purpose of a design.
So a site manager who tells a subcontractor to use a different fixing is modifying a design. So is the subcontractor who chooses one. The definition does not look at job titles. It asks who changed the design.
Site changes that are design
Substituting a product or component because the specified one is unavailable
Changing a fixing, a bracket or a connection so that it fits what is actually there
Simplifying or reordering a detail so that it can be built
Rerouting services around something the drawings did not show
What Regulation 9 asks of whoever makes the change
Regulation 9 sets out the designer's duties. When preparing or modifying a design, the designer must take into account the general principles of prevention and any pre-construction information to eliminate, so far as is reasonably practicable, foreseeable risks to the health or safety of anyone carrying out or affected by the construction work, maintaining or cleaning the structure, or using it as a workplace.
Where those risks cannot be eliminated, the designer must, so far as is reasonably practicable:
take steps to reduce or, if that is not possible, control the risks through the subsequent design process
provide information about those risks to the principal designer
ensure appropriate information is included in the health and safety file
The designer must also take all reasonable steps to provide, with the design, enough information about it to help the client, other designers and contractors comply with their own duties.
For a change made on site, that information is what most often goes missing. The original drawing still shows the old detail. The health and safety file, which exists so that people can work on the building safely in future, ends up describing a building that was never built.
The question after an incident
After something goes wrong, nobody asks whether the change was sensible. They ask who decided it, what they considered, and where it was written down. A marker-pen sketch on a drawing in the site cabin answers none of those.
A simple way to control site changes
This does not need a heavy procedure. It needs a few rules that everyone on site knows:
Decide who may change what. Name who can agree a change on site, and which changes must go back to the designer who owns that element.
Raise it, do not just do it. A query with the reason, a photo and the proposed change, sent to the right designer.
Record what was considered. What changed, why, who decided, and what risks the change introduced or removed.
Tell the principal designer. Any risk that could not be designed out goes to them, as Regulation 9 expects.
Close the loop. The drawing is revised, and anything the next maintenance team needs to know goes into the health and safety file.
Free checklist
Our one-page design review checklist lists ten things every design review comment should record, five questions to ask before anyone changes a detail on site, and three habits for every new revision. It is free, with no sign-up. More are on our free checklists page.
Where Clarity Markup fits
Clarity Markup is our drawing markup tool for construction. It keeps every revision cloud, dimension and comment as a separate object, so when the next revision arrives you carry across the comments that still stand instead of redrawing them, and the whole list exports as a comment schedule for the design team. It runs in the browser, and your drawings stay on your own machine.
See Clarity Markup, with seven days free and no card needed to start.
This article is general information, not legal advice.