In this highly litigious modern-day society that we live, arse-covering has turned into an art form. Liability is like a hot potato and it’s all about transferring it away from oneself and onto another party.

In engineering and architectural design that other party is usually the contractor. The designer is in a great position to pass the buck down the line wherever possible.

These common specification phrases may look familiar:

“in accordance with manufacturer’s instructions”
“contractor to use suitably compatible product”
“all work and installation to be undertaken in accordance with AS XXXX”

The above common specification phrases often impart key design detailing onto the contractor and leaves the exact design detailing ambiguous in a bid to limit liability and pass it on.

But is this in the best interests of the project?

Of course not.

When the tendency is to avoid what’s best for the project in preference of reducing liability, a misalignment of objectives is created.

Of course, this is standard industry practice which is so instilled in the habits of designers that it is not consciously considered one way or the other.

But by highlighting the risks of excluding specific construction details in designs, I hope to at least persuade some conscious thought about going over-and-above to improve project outcomes.

Firstly, let’s look at the risks of over-specification, that is, stipulating highly detailed designs usually passed onto the building contractor to determine. And whether you should continue to cover your butt or put it out in the open confidently for everyone to see.

Risks of Prescriptive Specifications

There are of course many legal consequences for over-specification. By providing highly detailed designs, a specifier inherits a great deal of additional liability and possible recourse if the design fails.

This may stem from a range of poor outcomes, some of which may include:

  • The design is not physically buildable
  • The design does not perform as intended
  • The design does not comply
  • The design leads to a building defect
  • The design unnecessarily stalls the program
  • The design is incompatible with surrounding building elements
  • The design is not appropriate for the surrounding environment or building elements.

In many scenarios, the builder may be in a position to better assess issues such as construction program and buildability. In these situations, some elements are best left to the contractor.

But where the design relates to the necessary performance and appearance of the finished product, then it makes more sense for the designer to step up and provide specify design details, over-and-above the typical “…install to AS XXXX”.

Risks of Performance Specifications

As a designer, you are probably considering the liability associated with over-designing. But are you considering the project risks associated with passing on design details to the contractor?

Some of the risks associated with under-specifying and its impact on project success may include:

Incorrect Design

Often, if the designer doesn’t design it, there is a chance that it will slip through the cracks until it’s installed. The foreman/installer/applicator on site on the day may end up designing it as they go. Unfortunately, they have a vested interest in getting the job done as quickly as possible, not as best as possible.

“I’ve been doing this for 40 years” is another possible scenario where the contractor may think they know how to correctly detail/install the item in question and have been using the same approach for decades. But times change, expectations change, standards change and design has a lot to do with context, so a one-size-fits-all approach is flawed.

Overlooked Design Considerations

Underestimation of technical expertise required in a design scenario may result in design considerations being overlooked.

Sometimes, the contractor just doesn’t have the theoretical technical expertise required to take on the design.

For example, the contractor can’t be expected to select a waterproofing membrane that will tolerate the structural deflection of a floor slab or differential movement of abutting elements without input from a structural or materials engineer.

It just isn’t their job to know the expected movement occurring at the interface of a 40 MPa concrete column next to a 5 MPa masonry brick infill panel which are sitting on a 25 MPa floor slab. So how can they be expected to select the correct waterproofing system that will tolerate the unique characteristics of the project?

The problem here is not that the builder then needs to have the conversation with the engineer, it is that the contractor doesn’t even know to ask the question.

Inadequate Manufacturer Knowledge

In the example above, often the contractor could approach the manufacturer for design support. The specification probably states: “install in accordance with manufacturer’s instructions”. But then sentence assumes a certain level of technical expertise from the manufacturer.

Let’s say the contractor finds a cheaper alternative from a lesser-known manufacturer from China who does not provide the support/technical knowledge required in such a complex application. For starters, it’s unlikely that a waterproofing company has a structural engineer on their books.

To me, the sentence “install in accordance with manufacturer’s instructions” is much like writing a blank cheque for project inadequacies.

Time Delays

Leaving the design to the contractor means that the design details are not ironed out until the construction phase. This can lead to problems associated with poor design planning.

For example, a balcony stepdown might be designed by the structural engineer but because the balcony tile bed may be the responsibility of the contractor, the tiler at the time may fail to consider required waterproofing termination heights. This may lead to project delays and/or rework which could have easily been avoided in the design phase.

Lack of Context

The designer is in a better position to understand the design context, surrounding elements and the appropriateness of details in the landscape of the entire project.

Without appropriate consideration for such factors, the project is left open to non-compliances, incompatibilities, poor performance and fire risks.

The Lacrosse building fire is an example of poor consideration for context. The combustible cladding panels used were actually compliant when used on other classes of buildings and may have been compliant if an alternative solution was included in the design to accommodate them.


All these project-related risks identified above lead to varying implications on one or more of the golden triangle elements of time, cost & quality.

In my view, there is a definite business case for over-specifying, that is, taking on more of the design and detailing responsibilities than is typically required at design stage. With proper procedures in place to ensure designs are rock solid and bullet-proof, designers can largely offset the increased liability associated with over-specifying.

Just some of the benefits that designers may reap by over-specifying include:

  • Minimisation of disputes;
  • Minimisation of delays;
  • Improved quality;
  • Minimisation of time expended on project management;
  • Improved profitability; and
  • Greater project success and reputation.

If you can be confident in your design efforts, this makes good business sense, and the chance of project success improves and that’s good for everyone.