Temporary works risk categories: CFR, DCR and ER explained

The temporary works risk categories used in Australia are CFR, DCR and ER: the consequence of failure risk, the design complexity risk and the execution risk. They come from the Temporary Works Risk Guidelines of the Temporary Works Forum Australia (TWfAU), and contract specifications are starting to require them. In short, CFR asks how bad a failure would be, DCR asks how complex the design is and so how hard it must be checked, and ER asks how easily the works could fail on site through how they are built, used or removed. By the end of this article you will know what each category means at each level, who proposes and decides them, and what each one changes for the brief, the design check and the controls on site.

Where the categories come from

The TWfAU is a community of practice within Engineers Australia. Its guidelines, reference TWfAU2020: 01, are an Australian adaptation of the UK Temporary Works Forum's 2014 clients' guide, published with that forum's permission [1]. The forum describes the work as an Australian first draft and has invited comment from industry [2]. The guidelines can be downloaded from Engineers Australia [1] [3].

The guidelines take the four design check categories of the British standard BS 5975 and extend them at both ends, which is where DCR00 and DCR4 come from [1]. If you have worked to BS 5975 categories 0 to 3 in the UK, DCR0 to DCR3 will feel familiar.

One thing to watch: the guidelines call the third category Execution Criticality Risk (ECR) in one place and Execution Risk (ER) elsewhere [1]. They mean the same thing. This article uses ER, as the South Australian specification below does.

CFR: consequence of failure risk

CFR describes what would happen if the temporary works failed, given what they are, where they are and what is around them [1]. It has four levels. In the guidelines' terms, paraphrased:

Category	What a failure would mean
CFR0	No real impact
CFR1	Low impact, contained within the site; inconvenient, with injury unlikely
CFR2	A potentially major effect, with possible deaths, injuries or significant economic loss, but no chain reaction beyond it
CFR3	Catastrophic in its own right, or small in itself but able to set off a chain of major incidents

The guidelines illustrate the difference with two excavations: a small one in a remote spot, and one whose failure could undermine a main railway line [1]. The excavation might be the same size. The consequence is not.

CFR is the category the site team knows best, because it depends on the site: the live services, the adjacent buildings, the rail corridor, the public footpath, the crane working beside the edge. That is why the guidelines expect it to be set by the client and stated in the design brief [1].

DCR: design complexity risk

DCR describes how complex the design is, and through that, how independent the design check has to be [1]. It has six levels:

Category	What it covers	Who checks the design
DCR00	Items a competent site team manages without a design, by custom and practice and a standard safe system of work, only where the CFR is CFR0 or CFR1	The site's method statement approval process
DCR0	Standard solutions, with CFR0 or CFR1	Another member of the site or design team
DCR1	Simple designs, with CFR0 or CFR1	Another member of the design team
DCR2	More complex designs, or simpler designs where the CFR is CFR2, or where separately managed schemes interact	A person not involved in the design and not consulted by the designer
DCR3	Complex or innovative designs, or designs that lead to complex sequences, where the CFR is not CFR3	A separate organisation not involved in the design and not consulted by the designer
DCR4	Exceptional, highly innovative designs beyond normal codes, and any scheme with CFR3	A separate organisation not involved in the design and not consulted by the designer

The checking column paraphrases the guidelines' table of check independence, which they base on BS 5975 [1].

The guidelines give examples at the lower levels. Kicker shutters and small single lift access scaffolds sit at DCR00. Shallow trenches, low formwork and scaffolds built to published tables without a bespoke design sit at DCR0. General formwork and falsework, and propping to openings in brickwork, sit at DCR1 [1]. The examples assume a normal CFR and ER [1]. Raise either, and the same item can move up.

The key link is between CFR and DCR. Where the CFR is CFR2 or CFR3, the brief should say so and the DCR should go up [1]. In practice, a design that would be checked by a colleague on an open site may need an independent checker beside a railway or an occupied building.

ER: execution risk

ER describes how likely a failure is through what happens on site: workmanship, materials, use and removal, from erection until the works are taken down [1]. It has four levels:

Category	What it describes
ER0	No identified practical way for the works to fail, and the CFR is CFR2 or below
ER1	Minor structures with plenty of robustness and redundancy, where the CFR is not CFR3
ER2	Conventional structures, where the CFR is CFR2 or below
ER3	Works that depend on critical structural or tension details, with little redundancy or an inherent instability, and any scheme with CFR3

ER is where the design meets the site. The guidelines expect the designer to state, in the design output, the controls and hold points needed to manage the ER, and allow the construction team to add more [1]. Where the CFR is high, they assume the designer will raise the DCR and the operations team will raise the ER [1].

Who proposes the categories and who decides them

The guidelines put the categories with the client: the client specifies and communicates them through the design brief [1]. Several parties are expected to think about CFR, including the client, the permanent works designer, adjacent asset owners and the principal and main contractors [1].

On an Australian project, the client in this sense is often the contractor. The South Australian Department for Infrastructure and Transport's specification PC-CN4 reads the guidelines' references to the client or project manager as obligations on the contractor [4]. For temporary works procured by a subcontractor, the same logic usually puts the categories with whoever commissions the design.

In practice:

The site team proposes the categories in the brief, with reasons. The temporary works coordinator (TWC), the person responsible for coordinating the temporary works on the project, makes sure the brief reflects the real site and its residual risks [4].
The designer reviews the brief and can ask for more information, which the client has to act on [1]. Where the designer is unclear, the guidelines expect the point to be resolved with the client and the brief updated [1]. A designer who thinks the DCR is too low should say so before design starts, not after.
The checker can reject the design if not satisfied with it [1].

The categories are a judgement made by the people responsible for the works. They are not a calculation, and the reasons matter as much as the label. A CFR2 with no explanation gives the designer and checker nothing to test.

What each category changes

The categories are not paperwork for their own sake. Each one changes something you have to do.

Category	What it changes
CFR	Whether the DCR and ER should be raised; for CFR2 and CFR3, the designer has to address the heightened risk and show how the design reflects it [1]; for CFR3, a peer review [1]
DCR	Whether a brief is needed at all (everything from DCR0 up needs one); whether the designer issues a design statement (DCR1 and up); how independent the checker must be; how much concept design work is expected; for DCR4, a peer review [1]
ER	The controls and hold points the designer states and the site adds; how hard you inspect before loading; for ER3, a peer review [1]

Peer review is the guidelines' response to the highest risk. For any scheme where the CFR is CFR3, the DCR is DCR4 or the ER is ER3, the guidelines say a peer review is appropriate, during concept design and again near the end of design [1]. For other schemes it is at the discretion of those managing the risk [1].

On site, the ER controls lead into the permit to load. The guidelines expect a permit to load before load is applied, such as before a concrete pour, and before temporary works load another structure [1]. They also say no one should sign a permit until they are satisfied about what can and cannot be inspected on site [1].

How a contract can make the categories mandatory

The SA specification PC-CN4 (version 1, 30 September 2024) is a clear example of the categories written into a contract [4]. It requires temporary works activities to follow the Engineers Australia guidelines [4]. It then requires the contractor's design management plan to say how each CFR, DCR and ER is determined, and how a DCR changes as the design develops or changes [4]. Design documentation must state the categories, and the controls and hold points for the ER, with who releases each hold point [4]. For CFR2 and CFR3, it must show that both the permanent and temporary works designers have considered the heightened risk [4]. Where peer review applies, the peer reviewer must be independent of the contractor and of all the designers [4].

That specification applies to its own contracts. Check your own contract and your company's temporary works procedure, which may set the categories, the check requirements and the permit process in more detail.

A checklist for proposing the categories

Before the brief goes to the designer:

State the CFR and why. Name what a failure would affect: services, structures, rail, roads, the public, other work on site.
Propose the DCR with the CFR in mind. If the CFR is CFR2 or CFR3, check that the DCR has been raised and that the checker's independence matches it.
Propose the ER and the controls you already know you will need. Staged excavation, a pour rate, a removal sequence, inspections before loading.
Flag any peer review. CFR3, DCR4 or ER3 points to one.
Ask the designer to confirm or challenge the categories in the design statement, so any change is recorded.
Plan the hold points and the permit to load around the ER before the works start, not on the day of the pour.

An invented example

Example Civil is digging a trench for a pipe on two sites. On the first, the trench runs across an open paddock with no services nearby. On the second, the same trench runs beside the boundary fence of an operating railway. The trench is the same, but the second brief would state a higher CFR, with the railway named as the reason, and propose a raised DCR so that an independent checker reviews the design. The site team would also expect the designer to set more hold points for the excavation stages. The categories in each case are proposals for the TWC and the designer to confirm, not a rule.

For what else goes in the brief alongside the categories, see how to prepare a temporary works design brief.

How TworkX handles the categories

TworkX proposes the CFR, DCR and ER, and the check category, from the information in the brief, each with its reasons, for the author to decide. It does not set them. The decision and the reasons go into the brief for the designer and checker to see. How it works shows where that happens, and the sample brief shows how the categories are printed.