Choosing the right one matters. Get it wrong and you risk overpaying or using a mix that isn’t suitable for the job. Here’s a straightforward breakdown of what each grade is used for and when to specify it.
What is GEN concrete?
GEN concrete refers to general-purpose mixes used mainly in non-structural or light structural applications. Unlike higher-strength grades such as C25 or C30, GEN mixes are designed for groundwork rather than heavy load-bearing structures. These designated mixes follow a recognised UK classification system, and you can read more about how concrete specifications are defined if you want a deeper technical explanation.
They are commonly used in domestic building projects, especially at early stages like foundations and sub-bases.
GEN 1 concrete: the weakest general-purpose mix
GEN 1 is the lowest strength of the standard GEN range. It’s often used where the concrete is not expected to carry structural loads.
You’ll typically see GEN 1 used for blinding layers beneath foundations, where it provides a clean, level surface for further construction work. It can also be used for kerbing, drainage surrounds, and other non-structural applications where strength is not critical.
In simple terms, GEN 1 is about preparation rather than support. It creates a stable base but isn’t designed to carry weight long-term.
GEN 2 concrete: light structural use
GEN 2 concrete sits in the middle of the range and offers more strength and durability than GEN 1. It is commonly used in domestic groundwork where there is some structural requirement but not heavy loading.
This includes strip foundations for smaller buildings, shed bases, and light domestic flooring. It provides a reliable balance between strength and cost, making it a popular choice for residential projects.
GEN 2 is often used when there is a need for a bit more confidence in performance without moving into higher-strength mixes.
GEN 3 concrete: stronger and more versatile
GEN 3 is the strongest of the GEN range and is widely used in domestic construction where more durability is required. It is suitable for foundations, floors and external works that need to withstand regular use and moderate loading.
You’ll often find GEN 3 used in house extensions, garage bases, patios and other areas where strength and longevity are important. It offers a solid step up from GEN 2 and is commonly specified for residential projects where performance matters over the long term.
While it is still classed as a general-purpose mix, GEN 3 is often close to entry-level structural concrete in practice.
How GEN concrete compares in practice
Rather than thinking of GEN 1, GEN 2 and GEN 3 as completely separate products, it helps to see them as a progression in strength and durability.
GEN 1 is mainly used for preparation and non-structural work. GEN 2 is suited to light structural applications. GEN 3 moves into heavier domestic use where strength and durability are more important.
The choice often comes down to how much load the concrete needs to carry and how long it is expected to perform under those conditions.
Common mistake when choosing GEN concrete
One of the most common mistakes is using GEN 1 where GEN 2 or GEN 3 is actually needed. While GEN 1 is cheaper, it isn’t designed for structural performance, and using it in the wrong place can lead to cracking or failure over time.
On the other hand, using GEN 3 for everything can push up costs unnecessarily, especially on simple groundwork where higher strength isn’t required.
Getting the balance right is key, and it often comes down to understanding what the concrete is supporting and how it will be used.
GEN 1, GEN 2 and GEN 3 concrete all have their place in construction, but they serve very different purposes. GEN 1 is for non-structural groundwork, GEN 2 covers light domestic applications, and GEN 3 is the strongest option for general residential use.
If you’re unsure which one is right for your project, it’s worth speaking to a supplier before ordering. The correct choice will save time on site, reduce cost and help ensure your project performs as expected over the long term.
