When it comes to building strong, reliable surfaces whether for driveways, garden paths, or construction foundations choosing the right road base material can make all the difference. In Australia, particularly across Sydney’s ever changing weather conditions, durability and drainage are key.

Two of the most commonly used materials in landscaping and construction are 10 mm blue metal and 20 mm blue metal. While they might sound similar, these materials perform quite differently depending on the type of project you’re working on.

In this guide, we’ll break down what blue metal is, the difference between 10 mm and 20 mm road base, when to use each, and how suppliers like Ace Landscapes & Turf Supplies help Sydney homeowners and contractors make the right choice.

What Is Blue Metal?

Blue metal, often called basalt or crushed rock, is a hard, durable stone widely used in construction, landscaping, and road base applications. It’s typically blue-grey in colour and is crushed to various sizes from fine dust to larger aggregates like 10 mm or 20 mm.

Blue metal is valued for:

• Strength and stability – it compacts well, making it ideal for sub-base layers.
  

• Excellent drainage – the gaps between stones allow water to pass through, reducing surface flooding.
  

• Versatility – suitable for driveways, garden paths, concrete mixes, and road construction.
  

In short, blue metal is a foundational material that keeps projects structurally sound, long-lasting, and safe.

Understanding Road Base

Road base is a blend of blue metal aggregate and fine materials (often called fines or crusher dust). It’s compacted to form a solid, stable foundation before laying concrete, pavers, or asphalt.

A properly prepared road base ensures your surface:

• Resists cracking or shifting
  

• Handles heavy loads
  

• Drains water efficiently
  

• Reduces maintenance over time
  

Sydney’s combination of wet winters and dry summers makes proper road base selection crucial; the right choice will protect your project from erosion and movement.

10 mm vs 20 mm Blue Metal - What’s the Difference?

While both materials are made from the same high-quality basalt, the particle size changes how each one behaves. Here’s a detailed comparison:

Size:
10 mm blue metal consists of smaller, finer stones, roughly 10 mm in diameter, while 20 mm blue metal uses larger stones about 20 mm across.

Compaction:
The 10 mm variety compacts tightly, creating a smooth and firm finish. In contrast, 20 mm blue metal is less compact and more porous due to its larger stone size.

Drainage:
10 mm blue metal provides moderate drainage suitable for most residential projects, whereas 20 mm blue metal offers excellent drainage, making it ideal for areas prone to heavy rainfall or water flow.

Surface Texture:
The surface of 10 mm blue metal is smooth and even, giving a neat appearance, while 20 mm blue metal has a rougher, more open surface texture.

Best For:
10 mm blue metal works best for driveways, garden paths, concrete mixes, and decorative areas. On the other hand, 20 mm blue metal is preferred for road base layers, drainage systems, and larger driveways that need greater strength and stability.

Load Bearing:
10 mm blue metal is suitable for light to medium loads, while 20 mm blue metal is designed to handle heavy vehicle areas or act as a strong sub-base layer.

In simple terms:

• 10 mm blue metal is perfect when you want a tighter, smoother surface.
  

• 20 mm blue metal is better for heavy-duty areas needing extra drainage and strength.
  

When to Use 10 mm Blue Metal

10 mm blue metal is one of the most versatile materials used in Sydney landscaping and construction. Its smaller size allows it to create a firm yet smooth base that’s easy to level and compact.

Common Applications:

1. Concrete Mixes
   

• The finer particle size ensures an even blend with cement, producing a smooth concrete finish.
  

• Commonly used in footpaths, small slabs, and garden edging.
  

2. Driveways and Pathways
   

• Creates a stable, aesthetically pleasing surface that’s easy to walk or drive on.
  

• Works well under paving stones or as a decorative gravel top layer.
  

3. Residential Landscaping
   

• Excellent for garden beds, borders, or as a filler under turf.
  

• Its neat finish suits modern landscaping designs.
  

4. Drainage Applications
   

• While not as open as 20 mm aggregate, it still offers good water flow for small garden drainage systems.
  

Pro Tip:
If you’re building a driveway or paved area in a residential Sydney suburb, 10 mm blue metal road base is typically the preferred choice; it compacts tightly and supports cars without loose stones moving under tyres.

When to Use 20 mm Blue Metal

20 mm blue metal is a heavier, coarser option ideal for high-traffic or load-bearing areas. Its larger particle size offers superior drainage and strength key features when dealing with heavy vehicles or unstable soils.

Common Applications:

1. Road Base Construction
   

• The larger stones create strong interlocking layers, essential for major roads, car parks, and commercial driveways.
  

2. Drainage Layers
   

• Excellent for retaining wall backfill, soak wells, and trench drains.
  

• Allows water to pass freely, preventing soil saturation and erosion.
  

3. Sub-Base Layers
   

• Often used beneath finer materials (like crusher dust or 10 mm blue metal) to provide a stable foundation.
  

4. Rural or Industrial Areas
   

• Ideal for rural properties or industrial yards where heavy equipment or trucks operate.
  

Pro Tip:
For Sydney projects that face frequent rainfall or heavy vehicle use, start with a 20 mm blue metal sub-base, followed by a 10 mm blue metal top layer for smoother compaction.

Pros and Cons Summary

10 mm Blue Metal:

This material offers a smooth finish, making it perfect for driveways and concrete applications. It’s easy to compact and provides a neat, professional look once laid. However, its smaller size means it offers slightly less drainage compared to larger aggregates.

20 mm Blue Metal:

Known for its excellent strength and superior drainage, 20 mm blue metal is ideal for areas that experience heavy loads, such as road bases or large driveways. The trade-off is that it has a rougher finish and can be harder to compact than 10 mm blue metal.

How to Choose Between 10 mm and 20 mm

When choosing between 10 mm and 20 mm blue metal road base, consider the following factors:

1. Project Type:
   

• Light-use areas → 10 mm
  

• Heavy-use or industrial areas → 20 mm
  

2. Drainage Needs:
   

• Poor-draining soil? Choose 20 mm.
  

• Stable, dry area? 10 mm is fine.
  

3. Surface Finish:
   

• For decorative or paved surfaces, 10 mm gives a neater appearance.
  

• For structural or hidden bases, 20 mm offers long-term stability.
  

4. Local Climate:
   

• Sydney’s coastal conditions can cause erosion using 20 mm for the sub-base helps improve resilience.
  

Blue Metal and Road Base in Sydney

In Sydney, blue metal and road base are used across a variety of residential and commercial projects:

• Driveways: Durable, long-lasting base that resists cracking.
  

• Garden Paths: Smooth walking surface with good drainage.
  

• Turf Preparation: Provides strong underlay for lawns and prevents water logging.
  

• Construction Foundations: Reliable material for slabs and retaining walls.
  

Given Sydney’s mix of clay-heavy and sandy soils, using the correct blend of 10 mm or 20 mm blue metal ensures long-term performance and safety.

Combining Blue Metal with Gravel and Other Materials

At Ace Landscapes & Turf Supplies, blue metal often works in combination with other materials to create functional and attractive outdoor spaces.

For Driveways

• Start with 20 mm road base for structural support.
  

• Add 10 mm gravel or crushed rock for smoothness.
  

• Finish with decorative gravel or compacted crusher dust for a polished look.
  

For Garden Paths

• Use 10 mm blue metal or fine gravel for even footing.
  

• Include edging to prevent spread and improve aesthetics.
  

For Drainage

• Combine 20 mm blue metal with sand and geotextile fabric in trenches for lasting water control.
  

This layered approach not only improves durability but also enhances the look of your outdoor spaces, a balance of function and style that Sydney homeowners appreciate.

Why Choose Ace Landscapes & Turf Supplies?

When it comes to quality landscaping supplies in Sydney, Ace Landscapes & Turf Supplies stands out as a trusted local provider with decades of experience.

Here’s why customers choose Ace:

Extensive Product Range

From gravel and blue metal to soil, sand, mulch, and turf, Ace offers everything you need for landscaping and construction under one roof.

Expert Advice

Their knowledgeable team helps customers choose the right product whether it’s 10 mm blue metal for a residential driveway or 20 mm road base for a commercial car park.

Local Sydney Focus

With years of experience supplying Sydney builders, landscapers, and homeowners, Ace understands local soil types, drainage challenges, and council requirements.

Quality and Consistency

All materials meet Australian standards for strength and durability, ensuring your projects last longer with minimal maintenance.

Convenient Delivery

Ace provides fast, reliable delivery across Sydney, including same-day or next-day service for most products.

Maintenance Tips for Longevity

To make your blue metal surfaces last:

1. Compact Properly:
   Use a mechanical compactor to remove air gaps and increase load capacity.
   

2. Ensure Proper Drainage:
   Always slope driveways or paths away from buildings to prevent pooling.
   

3. Top-Up as Needed:
   Over time, minor settling may occur adding a thin top layer every few years keeps surfaces even.
   

4. Keep Surfaces Clean:
   Regular sweeping prevents debris buildup and maintains appearance.
   

Whether you’re building a Sydney driveway, garden path, or commercial road base, choosing between 10 mm and 20 mm blue metal depends on your project’s strength and drainage requirements.

• 10 mm blue metal → smooth, compact, ideal for driveways and decorative areas.
  

• 20 mm blue metal → strong, porous, perfect for heavy-duty bases and drainage systems.
  

For expert advice and premium materials, trust Ace Landscapes & Turf Supplies your local Sydney specialists in gravel, road base, and blue metal.

Contact us to explore our full range or request a quote for your next landscaping project.