When you’re planning a building project, choosing the right concrete mix is one of the most important decisions you’ll make. GEN 1 concrete is a popular choice for certain types of foundation work, but what exactly is it, and when should you use it?
Understanding GEN 1 Concrete
GEN 1 concrete is a standardised concrete mix designed for specific construction tasks. The “GEN” stands for “general use,” and the number indicates its strength level. This concrete mix has a minimum compressive strength of 8-10 N/mm², which means it’s strong enough to support lighter loads but isn’t designed for heavy structural work.
Think of it like choosing the right tool for a job – you wouldn’t use a sledgehammer to hang a picture frame, and similarly, you wouldn’t use high-strength concrete where GEN 1 will do the job perfectly well.
What Is GEN 1 Concrete Used For?
GEN 1 concrete is specifically designed for non-structural applications in foundation work. Here are the most common uses:
Strip Foundation Blinding – One of the main uses is as a “blinding layer” beneath strip foundations. A blinding layer is a thin layer of concrete (usually about 50mm thick) that’s poured onto the bottom of a foundation trench. It creates a clean, level surface that protects the ground from weather damage and provides a solid base for the main foundation work to begin.
Light Domestic Applications –This concrete mix is ideal for pathways, domestic shed bases, light-duty garage floors, garden walls, and patio bases where heavy loads aren’t expected.
Why Choose GEN 1 for Foundation Work?
Cost-Effective Solution – Because this concrete mix has a lower cement content than stronger mixes, it’s more economical. When you’re doing foundation blinding or other non-structural work, there’s no point paying extra for strength you don’t need.
Easier to Work With – The mix has good workability, which means it’s easier to pour, spread, and level. For smaller building projects, this makes the job much more manageable.
Quick Setting – GEN 1 concrete sets relatively quickly, which means you can move forward with the next stages of your foundation work without lengthy delays.
GEN 1 vs Other Concrete Grades
To help you understand where GEN 1 fits in the range of options, here’s a comparison:
| Concrete Grade | Strength (N/mm²) | Best For |
|---|---|---|
| GEN 0 | 7.5 | Very light-duty blinding work |
| GEN 1 | 8-10 | Foundation preparation, pathways, and shed bases |
| GEN 2 | 10-15 | Domestic garages, workshops |
| GEN 3 | 15-20 | Floors, foundations for single-storey buildings |
| C20 | 20 | House foundations, floor slabs |
| C25 | 25 | Driveways, foundations |
Important Considerations for Foundation Work
When working on foundations, you must follow UK Building Regulations. The Planning Portal provides detailed guidance on building regulations for foundations, including requirements for depth, width, and specifications.
The type of soil on your building site affects what concrete you need. Clay soils can shrink and swell with moisture changes, which might require deeper foundations and potentially stronger concrete than GEN 1.
It’s always worth consulting with a structural engineer or building control officer for your specific project. They can confirm whether GEN 1 is suitable or if you need a different grade.
When NOT to Use GEN 1 Don’t use this concrete mix for main structural foundations (use C20 or higher), load-bearing walls, areas with heavy traffic or machinery, or projects requiring high compressive strength.
The Foundation Construction Process
Understanding where GEN 1 fits into foundation work helps you see its importance:
- Excavation: The foundation trench is dug to the required depth
- Blinding Layer: GEN 1 concrete is poured as a thin layer to create a clean, level base
- Damp-Proof Membrane: A protective layer is laid on top
- Main Foundation: Stronger concrete is poured to create the actual load-bearing foundation
- Building Work Begins: Once cured, construction of the walls can start
Working with Ready Mix Concrete Suppliers
When ordering this concrete mix, consider using a ready-mix concrete supplier. These suppliers deliver fresh concrete directly to your site, which offers several advantages:
- You get exactly the amount you need without waste
- The concrete arrives fresh and ready to use
- Professional mixing ensures consistent quality
- You can order different grades if your project requires it
Some suppliers use volumetric mixers that mix the concrete on-site, giving you even more flexibility with your order.
How Much Do You Need?
Calculating the right amount prevents waste and saves money. Use this simple formula:
Volume = Length × Width × Depth
For example, if you need a blinding layer that’s 5 metres long, 0.6 metres wide, and 0.05 metres deep (50mm), your calculation would be: 5 × 0.6 × 0.05 = 0.15 cubic metres.
It’s always wise to order about 10% extra to account for spillage and variations in the trench depth.
Quick Tips for Using GEN 1 Concrete
Protection from Weather – Like all concrete, it needs protection from heavy rain during the first 24 hours of curing. Cover freshly poured concrete with plastic sheeting if rain is expected.
Curing Time – This concrete mix typically reaches sufficient strength for light traffic after 24-48 hours, but full strength develops over 28 days.
Professional Quality – For foundation work, it’s almost always better to use ready-mix concrete from a professional supplier rather than mixing it yourself. This ensures consistent quality and proper proportions.
Getting Started with Your Project
If you’re planning foundation work that requires this concrete mix, here are your next steps:
- Check whether your project needs approval and ensure GEN 1 is appropriate
- Plan your schedule – foundation work should be done in suitable weather conditions
- Order in advance – book your concrete delivery for the right day and time
- Prepare the site with trenches ready and people on hand to help
- Work efficiently – concrete sets within a few hours, so work quickly once it arrives
Final Thoughts
GEN 1 concrete plays a vital role in foundation construction, even though it’s not the strongest mix available. For blinding layers, light-duty bases, and non-structural applications, it’s the sensible, cost-effective choice that gets the job done properly.
Using the right concrete mix for each part of your project is just as important as using the right strength. Whether you’re a DIY enthusiast working on a garden project or a builder preparing foundations for a new structure, understanding when and why to use GEN 1 concrete helps ensure your project succeeds.