Contraction joints control shrinkage cracks (preventing cracking), while expansion joints absorb thermal expansion and displacement (preventing deformation). The two have different design principles but both are structural deformation control measures.

A construction joint is a temporary joint for construction phasing, while an expansion joint is a permanent deformation joint (designed and pre-planned). The two are not interchangeable – the former is for construction needs, the latter for functional requirements.

Both control joints (to control shrinkage) and expansion joints (to absorb thermal displacement) are needed in buildings; expansion joints are mainly used in piping systems, while control joints are mostly used in concrete structures.

Expansion joints are used to absorb thermal displacement and structural deformation, while control joints are used to control concrete shrinkage cracks.  The two functions are complementary, but their application scenarios differ – both are needed in buildings.