What is the standard spacing for control joints in concrete flatwork?

The standard spacing for control joints in concrete flatwork is approximately 10 to 12 feet, depending on the thickness of the slab. This guideline is rooted in the goal of minimizing random cracking in the concrete, which typically occurs due to shrinkage as it cures.

Control joints are essential as they help manage the inevitable cracking by providing predetermined locations where cracks can form, as concrete expands and contracts due to temperature changes and moisture fluctuations. The specified distance of 10 to 12 feet is derived from field experience and well-established engineering principles that balance practicality and structural integrity. Keeping joints within this range ensures that enough reinforcement is provided in the concrete while allowing for movement without compromising the slab's overall performance.

When the control joints are placed too far apart, as suggested in the other options, it increases the risk of cracking occurring outside the established control joints, leading to uneven surfaces and greater repair costs. Thus, following the guideline of 10 to 12 feet promotes the longevity and aesthetics of the concrete flatwork.