Joints that separate slabs from walls and columns are called ___________ joints.

Joints that separate slabs from walls and columns are called ___________ joints.

• A. isolation
• B. expansion
• C. control
• D. construction

Answer: (A)

Joints that separate slabs from walls and columns are isolation joints. They’re placed at the interface to let the slab move independently from the surrounding structure due to shrinkage, temperature changes, or settlement, so stresses don’t transfer into the wall or column and cracks don’t follow the joint. The joint is filled with a flexible material to keep it unbonded and capable of movement. Expansion joints would handle movement from thermal expansion across larger spans, but they’re not specifically about isolating a slab from a wall or column. Control joints are inside the slab to control where cracks occur due to shrinkage, not at the interface with vertical elements. Construction joints are where pours are stopped and resumed, not about separating the slab from surrounding members.

Joints that separate slabs from walls and columns are isolation joints. They’re placed at the interface to let the slab move independently from the surrounding structure due to shrinkage, temperature changes, or settlement, so stresses don’t transfer into the wall or column and cracks don’t follow the joint. The joint is filled with a flexible material to keep it unbonded and capable of movement.

Expansion joints would handle movement from thermal expansion across larger spans, but they’re not specifically about isolating a slab from a wall or column. Control joints are inside the slab to control where cracks occur due to shrinkage, not at the interface with vertical elements. Construction joints are where pours are stopped and resumed, not about separating the slab from surrounding members.