Control joints in sidewalks should be spaced at intervals equal to what?

• A. Equal to the width of the slab
• B. Every 12 feet
• C. Equal to the thickness of the slab
• D. Every 8 feet

Answer: (A)

Control joints are placed to control where cracks will form as concrete shrinks and its temperature changes. For sidewalks, the standard practice is to space joints at intervals equal to the slab width. This creates roughly square panels, so any cracks that develop tend to run along the joints rather than across the surface, making them less noticeable and easier to repair. For example, a sidewalk that is 4 feet wide gets joints every 4 feet. Spacing every 12 feet or every 8 feet doesn’t align with the panel geometry and can lead to longer, uncontrolled cracks, while spacing equal to thickness would create overly frequent joints and unnecessary cost.