Yes, you can absolutely pour concrete in sections rather than all at once — and for many DIY projects like paths, patios, and shed floors, it's actually the preferred approach. Pouring in sections (using what tradespeople call construction joints or control joints) makes the job more manageable, reduces the risk of cracking, and lets you work at a pace that suits you. The key is planning those joints correctly from the start.
Why Pour in Sections?
Pouring a large slab in one go requires a big crew, a concrete pump or multiple ready-mix trucks, and fast, coordinated work before the concrete sets. For most homeowners tackling a driveway, garden path, or small floor slab, breaking the pour into sections is far more practical. It also gives you natural control joints that help manage the inevitable shrinkage cracking that occurs as concrete cures.
Benefits of sectional pouring include:
- Smaller, more manageable batches of concrete
- Less pressure on timing and finishing
- Easier to use a mixer or bagged concrete rather than a ready-mix truck
- Built-in control joints that reduce random cracking
Planning Your Construction Joints
The most important step is deciding where your joints will go before you start. Poorly placed joints can create weak points, trip hazards, or unsightly cracks.
General rules for joint placement:
- Space joints roughly 24–30 times the slab thickness apart. For a 100 mm slab, that's around 2.4–3 m between joints.
- Keep panels as square as possible — avoid long, narrow strips, which are prone to cracking.
- Place joints at natural break points: doorways, changes in direction, or where the slab meets a structure.
- For paths, a joint every 1.2–1.5 m is a good rule of thumb.
Use formwork (timber boards or purpose-made plastic edging) to create clean, straight edges between sections. Leave the formwork in place until the poured section has cured sufficiently — usually at least 24 hours, though longer in cold or wet weather.
Types of Joints
| Joint Type | Purpose | How It's Made |
|---|---|---|
| Construction joint | Separates pours done at different times | Formwork edge left between sections |
| Control/contraction joint | Encourages cracking in a straight line | Saw-cut or tooled groove, typically one-quarter of slab depth (confirm with your supplier or a qualified concreter) |
| Isolation joint | Separates slab from fixed structures | Foam strip or similar compressible material |
For most DIY sectional pours, a construction joint at the formwork edge doubles as your control joint — just make sure the edge is clean and vertical.
Preparing Each Section Correctly
Good preparation is just as important as the pour itself:
- Sub-base: Compact your base material (typically 100 mm of compacted AP20 or similar aggregate) thoroughly. A poorly compacted base is the number-one cause of slab failure.
- Moisture: Dampen the sub-base before pouring in hot or dry conditions to prevent the ground from drawing water out of the mix too quickly.
- Reinforcing: For structural slabs, use reinforcing mesh (REO) or steel bar as specified. Check with your local council whether your project needs a building consent — some concrete work is exempt under Schedule 1 of the Building Act, but it pays to confirm. Visit MBIE Building Performance for guidance.
- Existing concrete edges: When pouring against a previously cured section, clean the edge thoroughly. You can apply a bonding agent if you want the sections to bond together, or leave them unbonded (with a joint filler) if you want independent movement.
Mixing and Pouring Tips
- For small sections, bagged concrete mixes (available from Bunnings or Mitre 10) are convenient. For larger areas, a ready-mix truck is more economical and gives a consistent mix.
- A standard residential slab mix is typically 17.5–20 MPa (confirm the appropriate strength with your concrete supplier for your specific application), though driveways and areas with vehicle traffic often call for 25 MPa or higher. Check with your supplier.
- Don't add extra water to make the mix easier to work — this weakens the finished concrete significantly.
- Work each section fully before moving on: screed, float, and finish before the concrete stiffens.
Curing Your Sections
Curing is critical and often overlooked. Concrete needs to retain moisture to reach its full strength. After finishing each section:
- Cover with plastic sheeting or wet hessian for at least 3–7 days
- Avoid foot traffic for at least 24 hours, and vehicle traffic for at least 7 days (longer in cold weather)
- In hot, windy NZ summers, curing is especially important to prevent surface cracking
BRANZ has useful technical guidance on concrete construction best practice for NZ conditions.
When to Call a Professional
While pouring concrete in sections is well within reach of a capable DIYer for paths and small slabs, there are situations where you should engage a qualified concreter:
- Structural slabs (house floors, garage floors, retaining walls) — these may require engineering input and a building consent
- Large driveways — getting levels, falls, and reinforcing right is harder than it looks
- Any work near existing foundations or services — mistakes can be costly
- If you're unsure about sub-base preparation or reinforcing requirements
A licensed concreter will also know local soil conditions and can advise on the right mix and thickness for your specific site. You can find qualified concreters in your area on tradedirectory.co.nz.
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