Control joint
A control joint is a planned weakened plane in a concrete slab that guides where cracking occurs. Spacing under AS 3727.1: max 4 x slab thickness.
Ask Chalkline about this →A control joint is a planned weakened plane cut or formed into a concrete slab or wall to guide where cracking will occur as the concrete shrinks during curing. Rather than preventing cracking, a control joint concentrates it at a predictable, inconspicuous location.
Also known as: contraction joint, crack control joint, saw-cut joint.
In concrete driveways and paths governed by AS 3727.1:2016, control joints are typically saw-cut to one-third of the slab depth within 12 to 24 hours of pouring. Maximum spacing is 4 times the slab thickness: for a 100 mm slab, no more than 400 mm (practical maximum is 3 to 4 m in each direction for a residential driveway panel). Control joints differ from construction joints (which occur where two pours meet) and isolation joints (full-depth joints that separate a slab from a fixed structure such as a column or footing).
Category: Concrete
Related
- Residential driveways: vehicle crossings, slab specs, and surface options
- Slab on ground construction: residential build sequence
See also
Last updated: 2026-05-08. Verified: 2026-05-08. Quarterly review for currency.