Designed Concrete vs Prescribed Concrete
EN 206 recognises two fundamentally different ways to specify concrete, which shift responsibility for the mix between the specifier and the producer. This page explains the difference.
Designed concrete
For Designed Concrete, the specifier states the required properties and performance — strength class, exposure class(es), consistence (workability) class, maximum aggregate size, and any other project-specific requirements. The producer is responsible for selecting a mix composition that achieves those requirements, using their own materials and mix design expertise. This is the approach this site's calculator follows: you enter the performance requirements, and the calculation proportions a mix intended to meet them by the absolute-volume method.
Prescribed concrete
For Prescribed Concrete, the specifier states the exact composition instead — the constituent materials and their proportions, such as a fixed cement content and water-cement ratio. The producer's responsibility is limited to correctly batching and producing concrete to that stated composition; responsibility for whether the resulting concrete actually meets the project's performance needs sits with whoever specified the recipe, not the producer.
Why the distinction matters
The two routes place responsibility differently. With Designed Concrete, a producer who fails to meet the stated performance has not fulfilled the specification. With Prescribed Concrete, a producer who correctly produces the stated recipe has fulfilled it — even if the resulting concrete underperforms — because the specifier chose the composition. Most projects use Designed Concrete for exactly this reason: it puts the mix-design responsibility with whoever has the materials knowledge and testing capability, normally the producer.
Some national annexes add further named categories built on this base — for example the UK's BS 8500 annex adds Designated Concrete (a list of standard, pre-approved Designed Concrete mixes) and Standardised Prescribed Concrete (a small fixed list of standard recipes) as convenient variants for common applications.
Frequently asked questions
Which route does this calculator use?
Designed Concrete — you specify the performance requirements (strength class, exposure class, consistence, materials) and the calculator proportions a mix intended to meet them, in the same way a producer would develop a mix design.
Is Prescribed Concrete ever the better choice?
It can be, where the specifier already has a proven, well-tested recipe for very similar conditions and materials, or where full control over the exact composition matters more than shifting design responsibility to the producer. For most new designs, Designed Concrete is more straightforward.
Does EN 206 use the same category names in every country?
Designed and Prescribed Concrete are EN 206's own base categories and apply generally, but individual countries' national annexes can add their own additional named categories on top — check the annex that applies to your project.