Unless otherwise specified, what is the guideline for spacing contraction joints in concrete?

The guideline for spacing contraction joints in concrete is determined to help control cracking and manage the stresses that occur during curing and drying. The correct answer states that contraction joints should typically be spaced at 2.5 times the slab depth.

This means that if your concrete slab has a thickness of, let's say, 4 inches, the recommended distance between the contraction joints would be 10 inches (which is calculated as 2.5 multiplied by the slab depth). This specific ratio allows for an effective balance, providing sufficient control over cracking while not making the joints too closely spaced, which could minimize their effectiveness.

Contraction joints must be properly spaced to accommodate the natural shrinkage of concrete as it cures. If joints are too far apart, cracks can occur randomly across the slab, leading to potential damage and structural concerns. Therefore, using the 2.5 times slab depth guideline helps ensure that contraction joints are optimally placed to prevent such issues.