When should control joints be installed in concrete work?

Control joints are essential for managing the cracking that can occur as concrete dries and shrinks. Installing these joints before the concrete is finished, specifically before the edging and floating processes, allows them to be integrated into the slab effectively.

By placing control joints at this stage, the concrete can be shaped adequately to ensure proper placement and alignment, which helps in maintaining a uniform appearance and strength of the finished surface. This timing is crucial as it allows the joints to create weak points where cracks are more likely to occur, thus controlling the location and propagation of any potential cracking.

In contrast, installing control joints after the concrete has set or cured can lead to issues because they may not perform as intended and could disrupt the finish. Additionally, placing them during the pouring process wouldn't allow for the necessary adjustments or alignments that might be needed for optimal performance.