Which factor influences the positioning of the joints in a slab on grade?

• A. Sub grade conditions
• B. ALL OF THESE
• C. Finishing requirements
• D. Temperature

Answer: (B)

The placement of joints in a slab on grade is driven by the need to control cracking from shrinkage and temperature changes. Subgrade conditions matter because the soil beneath the slab governs how it settles and moves; uneven or poorly compacted subgrade can cause differential movement, so joints are positioned to intercept cracks where movement is likely. Finishing requirements matter because the surface finish and any patterns or alignments you need for doors, edges, or decorative work can influence where joints are placed so they don’t disrupt the finish or create weak points. Temperature plays a role since concrete expands and contracts with heat and cold; anticipating these movements helps determine joint spacing and depth to relieve stresses.

Because all of these factors affect how the slab will move and crack, the most accurate choice is that all of these influence joint positioning.