Planning a garden project and wondering which concrete to choose? GEN 3 concrete offers excellent strength, but is it the right pick for your DIY projects? Let’s look at what this mix does and when it makes sense to use it.
What Is GEN 3 Concrete?
GEN 3 is a high-strength concrete with a C20/25 rating. This means it reaches full concrete strength after 28 days of curing. It’s the strongest in the GEN range and delivers around 25% more power than GEN 2.
This structural-grade concrete is designed for demanding work where load-bearing matters. The mix balances cement, aggregates and water to achieve reliable strength and good workability.
Is GEN 3 Right for Garden Projects?
GEN 3 works well for garden projects that need extra durability. While it offers more than many general-purpose applications require, certain jobs benefit from this stronger mix.
When to Choose GEN 3
Consider GEN 3 for:
- Large shed bases storing heavy equipment
- Garage floors and domestic flooring for vehicles
- Bases for hot tubs or garden rooms
- Retaining walls holding back soil
- Areas facing freeze-thaw cycles or harsh weather
The higher concrete strength handles chemical attacks from de-icing salts better than weaker mixes. This freeze-thaw resistance makes it ideal for exposed areas.
When Lower Grades Work Fine
For lighter work, other concrete mixes may suit better. Simple stepping stones, small raised bed edging, a cold frame base, or decorative pathways often work perfectly with GEN 1 or GEN 2. Match the strength to what your garden’s designed structure actually needs.
Comparing Concrete Grades
| Grade | Strength | Best Garden Uses |
|---|---|---|
| GEN 0 | C7/8 | Stepping stones, light paths |
| GEN 1 | C10/12 | Shed bases, patios, driveways |
| GEN 2 | C16/20 | Heavy bases, domestic flooring |
| GEN 3 | C20/25 | Outbuildings, retaining walls |
Preparing Your Site
Good preparation ensures lasting results. The UK Planning Portal offers helpful guidance on foundation requirements for outbuildings.
Before pouring, you should:
- Remove topsoil and organic matter
- Excavate to proper depth (100-150mm for paths, deeper for structures)
- Lay and compact a hardcore sub-base
- Install formwork to contain the pour
- Add membrane for damp protection where needed
Avoid using wood pallets or other recycling materials as a sub-base—they break down and cause problems later.
Benefits of GEN 3 for Tough Jobs
When your project genuinely needs strength, GEN 3 concrete delivers:
- Superior load capacity for heavy equipment
- Freeze thaw resistance in exposed locations
- Protection against chemical attacks from de-icing salts
- Long-term durability with less maintenance
- Crack resistance when properly reinforced
The dense mix also resists damage from freeze-thaw cycles better than lighter grades. Some mixes include air entrainment, which creates tiny air bubbles that help handle temperature changes.
Calculating Your Needs
Work out volume by multiplying length × width × depth (in metres). A 3m × 2.5m shed base at 100mm deep needs:
3 × 2.5 × 0.1 = 0.75 cubic metres
Order slightly extra to cover uneven ground.
Getting the Right Advice
Choosing between concrete mixes doesn’t need to be complicated. Speak with specialists who can assess your specific needs. Soil type, expected loads and local weather all affect which strength of concrete works best.
Volumetric delivery creates the mix fresh on-site, so you pay only for what you use. This suits DIY projects where quantities vary.
Final Thoughts
GEN 3 concrete suits garden projects needing genuine structural strength—outbuildings, heavy bases and load-bearing structures all benefit. For lighter work like stepping stones or a raised bed surround, lower grades often do the job at less cost.
The key is matching concrete strength to actual demands. When unsure, ask the experts for advice that ensures your garden project lasts for years.
