The Structural Designer's Risk Assessment under CDM 2015
What structural designers record, how to present it and what to leave out
A structural designer's risk assessment records the significant risks the design creates or can remove, what the designer did about them and what remains for others to manage. It is easy to produce and easy to get wrong, because the entries that look diligent are often the generic ones. This guide takes the structural angle on regulation 9: the duties, the topics that belong on a structural register, how to present the information on drawings and in a register, and what to leave out.
Regulation 9 asks the designer to remove what can be removed, reduce what remains and pass on what is left. For a structure that means decisions about form, sequence and temporary stability, recorded where the contractor will read them.
What does CDM 2015 require of a structural designer?
Regulation 9 requires the designer to eliminate foreseeable risks so far as is reasonably practicable, reduce or control those that remain, tell the principal designer and put appropriate information in the health and safety file, and give enough information with the design to help others comply.
CDM 2015 does not require a document called a designer's risk assessment. Regulation 9 requires the designer to think about risk while designing, to act on it and to pass on information. A register is the usual way to evidence that. This guide takes the structural angle on the duties and leaves the general register structure to the existing guide to the designer's risk assessment.
The four duties in regulation 9 run in a fixed order. Before starting, the designer must be satisfied that the client is aware of its duties under the Regulations. 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 anyone carrying out or liable to be affected by construction work, anyone maintaining or cleaning a structure, and anyone using a structure designed as a workplace. If risks cannot be eliminated, the designer must, so far as is reasonably practicable, take steps to reduce or control them through the design process, provide information about them to the principal designer and ensure appropriate information is included in the health and safety file. The designer must also take all reasonable steps to provide, with the design, sufficient information about the design, construction or maintenance of the structure to help clients, other designers and contractors comply with their duties.
HSE's guidance on designers' roles and responsibilities confirms that designs include drawings, design details, specifications, bills of quantity and design calculations, so a structural engineer who produces calculations and a specification is a designer in every sense the Regulations use. So is a steelwork contractor designing connections, or a precast supplier designing units. The duties apply to work for domestic clients as well, although the client's duties normally pass to the contractor or principal contractor.
- 01
Eliminate
Remove the hazard by design where it is reasonably practicable. The decision is usually made early, when form, ground and sequence are still open.
- Illustrative example
- Revising a basement layout so a deep, unsupported excavation next to a party wall is not needed
- Where recorded
- Design decision log, risk register
- 02
Reduce
Make the hazard smaller where it cannot be removed.
- Illustrative example
- Splitting a heavy element into smaller pieces so a lift is lighter and easier to site
- Where recorded
- Drawings, risk register
- 03
Control
Manage what remains through the design process itself.
- Illustrative example
- Specifying a sequence and temporary restraint for a cantilever until the structure behind it is complete
- Where recorded
- Sequence note, specification clause
- 04
Inform
Give the principal designer and the contractor what they need about the remaining risk, and put maintenance information in the health and safety file.
- Illustrative example
- Showing the location of post-tensioned tendons so later drilling avoids them
- Where recorded
- Drawings, health and safety file
The examples are illustrative design responses, not a list to copy. What counts is that the order is followed: eliminate before reduce, reduce before control, and inform about whatever is left.
What do structural designers typically record?
Temporary stability, excavations and basements, heavy or awkward lifts, demolition and alteration sequence, hazardous materials in existing structures and anything about the structure that matters for maintenance and future work, each stated specifically.
Structural designers most often record temporary stability, excavations and basements, heavy or awkward lifts, demolition and alteration sequence, hazardous materials in existing structures and anything about the structure that matters for maintenance and future work. Each entry should describe a hazard particular to this design.
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| Topic | What to record, specifically | Usually on |
|---|---|---|
| Excavations and basements | Temporary stability of the excavation and retaining structure, assumed sequence, support from the permanent structure at each stage, adjacent structures and movement limits, groundwater | Sequence drawings, specification, pre-construction information |
| Lifting and heavy or awkward elements | Elements that need a particular installation sequence, lifting points or lifting restrictions, and anything where the lift zone cannot be at the usual position | Drawings, precast or steelwork schedules |
| Working at height | Edge protection that the design provides or needs, fragile roof materials, access for maintenance and cleaning, and erection details that avoid unusual work at height. Leave out the generic hazard | Drawings, health and safety file |
| Temporary stability during construction | Cantilevers, frames that rely on cores or bracing built later, transfer structures, walls and slabs that need propping, and strength conditions for striking props | Sequence drawing, temporary works information |
| Demolition and alteration sequence | The structural form of the existing building, load paths, elements carrying stored energy such as prestressed or post-tensioned members, the order of removal assumed, and temporary support required | Structural demolition and alteration drawings, specification |
| Hazardous materials | Asbestos and other hazardous substances identified in surveys, and where the design avoids disturbing them or relies on removal first | Pre-construction information, survey references on drawings |
| Ground and existing services | Unusual ground, contamination or obstructions, existing services in the way of foundations or excavations | Pre-construction information, drawings |
| Proximity and access | Railways, live highways, overhead lines or occupied buildings that constrain cranes, piling or lifting | Site plan, drawings |
| Maintenance and future work | Items that need to be known for maintenance, alteration or demolition: tendon locations, hidden steel, special fixings and design loads | Health and safety file |
Illustrative topic list for a structural register. Whether a topic belongs depends on the project: the test is whether a competent contractor or facilities manager would miss it, or manage it differently, if the designer did not say.
Temporary stability and sequence
This is the topic the structural designer is best placed to cover, and the one most often left to the contractor. Any structure that is only stable once something else exists (a core, a slab, a retaining wall's top prop) has a construction state that differs from the completed state. The register entry should say which element depends on which, what the assumed order is and what the contractor must not alter without referring back. The same information feeds the contractor's temporary works brief, covered in the guide to the temporary works design brief.
Demolition, alteration and existing structure
On refurbishment, the greatest unknown is usually the existing structure. Record what was surveyed, what was assumed and what could not be seen. Where the design relies on removing elements in a particular order, or on keeping elements that carry load, say so, and give the temporary support the design assumes. Where an existing member is prestressed or post-tensioned, the entry should flag that cutting or opening needs a planned approach. Hazardous materials found in surveys belong in the pre-construction information. The register should point to them where the design takes decisions to avoid disturbing them.
Lifting, heavy elements and erection
Where the structural design puts a heavy or awkward element in a place that constrains lifting, the entry should say what is constrained and why. For steel and precast, the designer can often reduce risk by detailing: connections that can be made safely from an erected position, elements split into practicable pieces, or lifting points that are known. The connection design may sit with the fabricator, so the information needs to reach them. The guide to steel connection design responsibility covers how.
Maintenance and use
Regulation 9(2) includes people maintaining or cleaning a structure and people using it as a workplace. For structures this means access to bearings, joints and anchorages that need inspection, roof edges and parapets, and any component that needs replacement. Record what the design provides, and put what the facilities manager needs in the health and safety file.
Where should the assessment be recorded: on drawings or in a register?
In both, from one source. Hazards and sequence notes go on the drawings where the contractor will read them, requirements go in the specification, and the register holds the residual risk, owner and status and points to the drawing or clause.
Put the hazard at the point of use on the drawing, put the requirement in the specification and use the register to hold the residual risk, owner and status. The register points to where the information lives and does not repeat it. HSE guidance on CDM notes that key information can be put on drawings or in models, and the register should not duplicate it.
A sequence note beside the relevant detail will be read by the person building the work. A register entry will be read by the principal designer, the client and whoever compiles the health and safety file. Both are needed, and both should come from one source so they cannot disagree.
Drawing
Wall W3 is stable only with props in place until level 2 slab reaches the strength stated in the specification. Do not remove props earlier without referring to the Engineer.
Register
Temporary instability of wall W3 during excavation. Design action: sequence stated on S-310. Residual: temporary works design required. Owner: structural engineer.
The drawing note speaks to the person on site and the register entry speaks to the principal designer. They must say the same thing. [Illustrative wording.]
- 1
Concept and early design
Decisions that eliminate risk: structural form, ground strategy, sequence, location of heavy elements. Record the decision and the reason.
- 2
Spatial coordination
Confirm which risks remain. Start the register against structural drawings and agree its format with the principal designer.
- 3
Technical design
Complete the entries. Put hazards and sequence notes on drawings and in the specification where the contractor will read them.
- 4
Pre-tender
Check the register against the issue drawings and specification. Pass residual risks to the principal designer for the pre-construction information.
- 5
Construction
Update for RFIs, contractor proposals and design changes. The designer who makes a change owns the risk it creates.
- 6
Handover
Pass maintenance and future-work information to the health and safety file.
Early entries record design decisions that remove risk. Later entries record what remains. The register is reviewed at each stage, before tender and when design changes arrive during construction.
What goes where
- Drawings
- Hazard and sequence notes at the point of use, lifting restrictions, locations of tendons and other items needed for future work.
- Specification
- Requirements for the contractor: temporary works procedure, submissions the engineer must see before work proceeds, sequence conditions and hold points.
- Register
- Significant residual risks, with owner and status, a pointer to the drawing or clause, and a flag for the health and safety file.
- Pre-construction information
- Survey results, ground information and hazardous material information the designers received, and the residual risks passed to the principal designer.
- Health and safety file
- What maintenance and later alteration will need: structural form, loads, tendon and hidden steel locations, special fixings.
What should not go in a structural designer's risk assessment?
Generic hazards that a competent contractor manages routinely, risks that the design does not affect and the contractor's own method detail. Each entry should name the element, the location, the design response and where the detail lives.
Leave out generic hazards that any competent contractor manages as a matter of course, risks that are not affected by the design, and detail that belongs in the contractor's own method statement. HSE guidance on CDM says detail should be proportionate to the risks that remain, and that listing insignificant risks is not an effective way to alert anyone.
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| Weak entry | Stronger entry (illustrative) |
|---|---|
| Working at height: contractor to use appropriate access | Roof edge at level 6 has no parapet to the design height at the stair core. Design provides edge protection anchors at 1.5 m centres. See S-402 [illustrative values] |
| Manual handling: contractor to follow safe working practices | Precast stair flights are heavy and awkward to turn in the core. Flight weight and lifting points are on the schedule, and the core is sized for lifting in at level 2 [illustrative] |
| Temporary works required | Wall W3 is unstable during excavation until the top prop is installed. Sequence on S-310. Contractor's temporary works design must account for this, and the Engineer reviews the effect on W3 |
| Existing structure may be unsound | Slab at level 1 was not exposed over zone C. Design assumes the 1960s as-built drawings and a loading survey. Opening-up is required before strip-out in zone C |
The weak entries are true and tell the contractor nothing new. The stronger entries name the element, the location, the design response and where the detail lives. Wording and figures are illustrative only.
Stay in your lane
The designer's register records design decisions and residual risk. It does not describe how the contractor should do the work, and it is not a method statement. The contractor's risk assessments and method statements deal with the means and methods of construction. They should connect to the register, because they start from the designer's information, but they are separate documents with separate owners. A designer who prescribes methods risks taking on responsibility that the contractor should hold, and a designer who stays silent on a hazard the design created leaves a gap.
A hazard without a response is half an entry
An entry that lists a hazard with no design action and no residual risk statement says only that the designer noticed it. Each entry should record what the designer did about it and what the designer thinks is left. If the answer is that nothing could be done, say so and say why.
Do not use the register to move risk
Passing every hazard on as residual risk does not meet the duty to eliminate and reduce. Where the structure can be changed to remove a hazard at reasonable cost, regulation 9 expects the designer to consider that first.
How does it link to the principal designer and the contractor's side?
The structural designer agrees the format and review points with the principal designer and passes on residual risks for the pre-construction information and health and safety file. Temporary stability entries feed the contractor's temporary works brief.
The principal designer plans, manages, monitors and coordinates health and safety in the pre-construction phase, and the structural designer feeds it. The designer agrees with the principal designer how information will be shared, and passes on residual risks for the pre-construction information and the health and safety file.
In practice that means agreeing one register format across the team, or a way to merge discipline registers, agreeing what goes on drawings and what stays in the register, setting review points at each design stage and before tender, and fixing how risks flow into the pre-construction information and later the health and safety file. The principal designer's duties are covered in the principal designer duties guide. The roles of the CDM principal designer and the Building Regulations principal designer on a higher-risk building differ, and the guide to CDM and Building Regulations principal designers explains how.
Links to the contractor's side
The register's temporary stability entries lead into the contractor's temporary works procedure. The coordinator will issue a brief to the temporary works designer after consulting the permanent works designer, and the information in the register and on the drawings is what the structural designer contributes. See the temporary works design brief guide. Where design is delegated to a contractor, such as steel connections or precast units, the delegated designer has its own regulation 9 duties, and the information that the engineer gives should include the hazards that the engineer has identified. See the design responsibility matrix guide for how to record who designs what.
Golden thread and change
On higher-risk buildings, the structural design information is part of the record that supports the golden thread, and risk information should move with it. The guides to the golden thread and higher-risk buildings cover the framework. Change during construction is where risk entries go out of date, so each change that affects the structure should trigger a check of the register. The specification change control guide sets out a method.
Questions engineers ask about the designer's risk assessment
Does CDM 2015 require a designer's risk assessment document?
No document of that name is required. Regulation 9 requires designers to eliminate, reduce or control foreseeable risks through design and to provide information. A register is the most practical way to evidence that, and on a small project the information may be short notes on drawings.
What hazards should a structural designer record?
Significant, design-specific hazards: temporary stability and sequence, excavations and basements, heavy or awkward lifts, demolition and alteration sequence, hazardous materials in existing structures, and information needed for maintenance and future work.
Should working at height go on a structural designer's register?
Only where the design creates something specific, such as an unusual roof edge or high-level access that needs maintaining. A generic entry telling the contractor to use suitable access does not alert anyone to anything.
Where should the information be recorded, on drawings or in a register?
Both, from one source. Put hazards and sequence notes on the drawings where the contractor will read them, put requirements in the specification, and use the register for residual risks, owners and status, pointing to the drawing or clause.
Who receives the structural designer's risk information?
The principal designer, who coordinates pre-construction health and safety, for the pre-construction information and the health and safety file. Contractors and other designers also need it, and it goes with the design.
Do the duties apply on domestic projects?
Yes. HSE says working as a designer for a domestic client is no different from working for a commercial client. The client's duties normally pass to the contractor or principal contractor, and the designer works to them as client.
Where Avoice fits
Most structural risk registers start specific and drift towards generic, and drift away from the drawings they describe.
Avoice now writes structural specifications alongside architectural and building services work. The Compliance module includes a CDM designer's risk register that records significant risks against drawings and specification clauses, with owners, status and a flag for items that belong in the health and safety file, and it can be shared with the principal designer. The existing guide to the designer's risk assessment and the CDM risk register page describe how it works. Practice Rules can require that a sequence or stability clause points to its drawing, and the pre-issue Technical Review compares the specification with schedules and drawings, which helps catch a risk entry whose drawing has been revised.
Software can structure and flag. The structural designer decides what is significant and what can be designed out, and the principal designer coordinates.