Here's a truth every concreter knows: all concrete cracks. It shrinks as it dries, and it moves with temperature and ground movement. Joints don't stop cracking. They decide where the cracks go, so you get a neat straight line in a joint instead of a jagged crack across the middle of your new driveway.

On a new home, joints matter most on the driveway, paths, alfresco and any other external slabs. Get them right before the pour and you'll save yourself a lot of disappointment later.

C5 - Pre Pour Slab Inspection Checklist

$119.00 AUD

Last updated 21 Oct 2026 · Revision 3 · Free updates for life

Checklist Type: Major (Base Stage)

Form Factor: Fillable, print-ready PDF (A4, 22 pages)

When to use: Base stage: after the slab is prepped, before concrete is poured

A 95-point pre-pour slab checklist. Check setbacks, boxing, membrane, pipes and steel after the slab is prepped and before concrete is poured, while fixes are still simple.

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The four types of joint

Control joints (contraction joints)

These are the lines you see across driveways and paths. They create a deliberate weak line so that when the concrete shrinks and cracks, it cracks there, out of sight in the joint.

  • Usually saw cut a few millimetres wide once the concrete is hard enough to cut cleanly without tearing the edges, typically within hours of the pour depending on the weather.
  • They can also be tooled into the wet concrete with a grooving tool, or formed with a strip set into the concrete.
  • Depth should be about a quarter of the slab thickness. Too shallow and the crack goes somewhere else.
  • Timing matters. Cut too late and the slab may already have cracked on its own.

Construction joints

A construction joint is simply where one pour stops and the next one starts, for example when a big driveway is poured over two days. It's not about controlling shrinkage cracks. The joint is detailed so the two sections stay level and work together, often with dowels or reinforcement across the joint as the design requires.

Isolation joints

An isolation joint fully separates the slab from something else so the two can move independently. Common spots on a home:

  • where the driveway or path meets the house slab
  • around pits, drains and service pits
  • against retaining walls, kerbs and footpaths

A compressible filler strip runs the full depth of the slab, and the top is usually sealed with a flexible sealant to keep water and dirt out.

Expansion joints

Expansion joints allow for the concrete to expand and contract with temperature. They're similar to isolation joints, with a compressible filler and a flexible sealant. On house-size driveways and paths, the isolation joints at the house slab and other fixed structures often do this job, along with the control joints. Large slabs and long runs may need dedicated expansion joints, as the designer specifies.

How far apart should control joints be?

For residential driveways and paths, the guidance in Australia comes from AS 3727.1 (residential pavements) and the Cement Concrete & Aggregates Australia (CCAA) guides. As a rule of thumb:

  • For a typical 100 mm driveway, control joints should be no more than about 3 m apart, and closer for thinner slabs.
  • Panels should be as close to square as practical. Long, skinny panels crack.
  • Put a joint at re-entrant corners (the inside corner of an L-shape) and where the slab changes width, such as at a narrow section beside the house.
  • Line joints up with each other and with corners of pits where possible.

Your house slab is different. It's designed by an engineer under AS 2870 for your site's soil class, and any joints are shown on the engineering drawings. Follow the engineer, not a rule of thumb.

What to check before the pour

  • Joint layout is shown on the plan or agreed with the concreter before they start.
  • Isolation joints are in place against the house slab, pits and retaining walls.
  • Joints are planned at re-entrant corners and changes in width.
  • You know when the saw cuts will happen (the same day, in most conditions).
  • Sealant at isolation joints is included in the price.

What cracking is acceptable?

Fine shrinkage cracks, especially ones running along a joint, are normal and expected. Cracks that are wide, keep growing, have one side higher than the other, or appear well away from the joints are worth raising with your builder. The QBCC publishes standards and tolerances for cracking in concrete, which is a good reference if you're not sure.

My C5 Pre Pour Slab and C6 Post Pour Slab checklists cover what to look at before and after your slab is poured.

Three things to remember

  1. Joints don't stop cracking. They control where it happens.
  2. Agree on the joint layout before the pour, not after.
  3. Keep isolation joints between your driveway, the house slab and other fixed structures.