What is the real cost of a shorter design life?
When choosing an engineering solution, the initial cost is often an important consideration. But the price paid at the start of a project does not necessarily reflect the overall cost of that solution over its lifetime.
This is where design life becomes important.
Design life is a key consideration when developing an engineering solution. It defines how long a component is expected to perform its intended function and influences decisions around materials, construction and protection. Different environments and applications will have different requirements, so understanding the design life objective is essential when selecting the right solution.
A longer design life can require greater investment at the outset. However, a solution with a shorter design life may need to be replaced more frequently, creating additional costs over time. Those costs can include materials, labour, access to site and installation, as well as the impact of inflation on future work.
For example, a component designed for a 10-year life could require significantly more interventions over a 100-year period than a solution designed to last 100 years. The initial price may look very different, but so can the whole-life cost.
There is also more to design life than what appears on the final price.
The engineering decisions that help a product achieve a longer life are not always visible once it is installed. Material selection, wall thickness, surface preparation, galvanising and additional protective coatings can all contribute to long-term performance. What may look like a straightforward product can therefore involve significant consideration behind the scenes.
Cockett Wick provides a good example of why these decisions matter.
As part of the Cockett Wick Sea defence scheme in Essex, KITE Projects worked with BAM UK & Ireland and the Environment Agency to provide a pedestrian safety solution for the new flood defence infrastructure.
The scheme required a galvanised steel handrail with a design life of 50 years. As galvanising alone would not provide the required longevity, KITE Projects explored a range of alternative solutions to achieve the required design life. The customer ultimately selected a stainless-steel solution, which whole-life costing showed to be an effective choice for the scheme. (https://www.kite-projects.co.uk/projects/cockett-wick)
The wider project also demonstrates how decisions made during design can contribute to longer-term sustainability. Measures included the use of recycled steel piles, alternative methods of transporting rock and the reuse of surplus materials.
The cost of replacement can also extend beyond the asset itself. Returning to a site means another period of engineering work, which can disrupt the operation of a network and affect the people and businesses around it. On projects in coastal, transport or public environments, repeated intervention can have a wider social and economic impact that is difficult to capture in an initial project price.
This is why design life should be considered as part of whole-life value rather than simply as a technical specification.
