Concrete is one of the most widely used building materials in New Zealand — and learning how to mix and use it properly is a must for any DIY project.
Whether you're setting fence posts, building a small slab, or tackling a backyard project, knowing how to make concrete in NZ can save you time and money.
In this guide, we’ll walk you through concrete mix ratios, tools, and step-by-step instructions, along with practical tips for working in Northland and Whangārei conditions.
What Is Concrete?
Concrete is made by mixing:
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Sand
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Aggregate (gravel)
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Water
Once combined, it forms a strong, durable material that hardens over time.
Concrete is used in many DIY projects, including:
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shed foundations
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pathways
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small slabs
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retaining structures
Concrete Mix Ratios (NZ DIY Guide)
Getting the mix right is critical for strength and durability.
Standard DIY Concrete Mix Ratio
The most common mix used in New Zealand is:
1 part cement : 2 parts sand : 3 parts aggregate
This is suitable for most general DIY projects.
Stronger Concrete Mix (For Posts & Slabs)
For extra strength:
1 : 1.5 : 3 (cement : sand : aggregate)
Use this for:
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fence posts
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structural footings
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small slabs
Quick Tip
Always add water gradually — the mix should be:
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firm
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workable
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not too runny
Too much water weakens the concrete.
What You Need to Make Concrete
You don’t need expensive tools — most DIY concrete jobs can be done with basic equipment.
Materials:
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Cement
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Sand
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Aggregate (or premix)
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Clean water
Tools:
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Concrete mixer, wheelbarrow or mixing tray
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Shovel
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Bucket
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Level
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Timber for boxing (formwork)
At Renovation Warehouse Whangārei, you can find a wide range of materials to support your DIY projects, including timber for boxing, posts, and construction supplies.
Step-by-Step: How to Mix Concrete by Hand
Step 1 – Prepare Your Area
Choose a flat mixing area or use a concrete mixer or wheelbarrow.
Make sure everything is ready before you start — once mixed, concrete begins to set quickly.
Step 2 – Mix Dry Ingredients
Combine:
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cement
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sand
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aggregate
Mix thoroughly until the colour is consistent.
Step 3 – Add Water Slowly
Create a small crater in the mix and gradually add water.
Mix continuously until you reach a firm, workable consistency.
Step 4 – Use Immediately
Once mixed, use the concrete straight away.
Most mixes begin setting within 30–60 minutes, depending on temperature.
How to Pour Concrete (DIY Basics)
For Fence Posts
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Dig your hole (typically 600mm deep)
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Position the post
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Pour concrete around it
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Check alignment with a level
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Allow to set
If you're building a fence, see our guide here:
https://renovationwarehouse.co.nz/blogs/news/how-to-build-a-wooden-post-and-rail-fence-a-step-by-step-guide
For Slabs or Paths
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Build timber boxing
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Level the ground
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Pour concrete evenly
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Smooth with a straight edge
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Finish with a trowel
Tips for Working With Concrete in Northland
Work Early or Late in the Day
Northland heat can cause concrete to set too quickly.
Keep It Moist While Curing
Lightly dampen concrete to prevent cracking.
Avoid Heavy Rain
Too much water can weaken the surface.
Common Mistakes to Avoid
Adding Too Much Water
This weakens the concrete and reduces durability.
Not Mixing Properly
Uneven mixes lead to weak spots.
Rushing the Finish
Take time to level and smooth for best results.
Why DIY Concrete Is Worth It
Learning how to make concrete allows you to:
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save money on labour
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complete multiple DIY projects
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improve your property
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build long-lasting structures
It’s one of the most useful DIY skills in New Zealand.
Why Renovation Warehouse Is Your First Stop for DIY Projects
If you’re planning a project that involves concrete, fencing, decking, or building work, Renovation Warehouse Whangārei should be your first stop.
You’ll find:
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affordable building materials
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timber for boxing and framing
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posts for fencing projects
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reclaimed materials for cost savings
Start Your Concrete Project Today
Now you know how to mix and use concrete, you’re ready to tackle your next DIY project.
Whether it’s setting fence posts, building a slab, or creating something new in your backyard, having the right materials and knowledge makes all the difference.
Visit Renovation Warehouse Whangārei and get started today.
FAQ – Concrete NZ
What is the correct concrete mix ratio in NZ?
The most common mix is 1:2:3 (cement, sand, aggregate) for general DIY use.
How long does concrete take to set?
Concrete usually begins to set within 30–60 minutes and fully cures over several days.
Can I mix concrete without a mixer?
Yes — most DIY jobs can be done using a wheelbarrow and shovel.
How much water should I add to concrete?
Add water slowly until the mix is firm and workable — not runny.
What is concrete used for in DIY projects?
Concrete is commonly used for fence posts, slabs, paths, and foundations.