Expansion joints are categorized into three types: expansion joints, settlement joints, and seismic joints.
 

Expansion joints: Due to changes in temperature and humidity, building components may undergo expansion and contraction deformation. To address this, vertical gaps are typically set at appropriate locations in the structure. The walls, floor slabs, and roofs of the building are then disconnected from the foundation upwards, separating the structure into several independent sections. For joints set to overcome excessive temperature differences, the foundation may remain undisturbed, with the structure being broken along the structural line from the top of the foundation to the roof.

Settlement joints: Architectural construction joints designed to prevent uneven settlement-induced cracking in walls or other structural components when there is a significant difference in height between parts of the same building, uneven distribution of loads, or when constructed on different soil foundations. These joints divide the building into several sections, each forming a separate system, with no connection between the foundation, walls, floors, and roof. The width of the joint is typically 70-100 millimeters. A vertical gap that completely separates a building or structure into sections from the foundation to the top, to avoid cracks caused by uneven下沉 in the different sections. Usually located between sections with significant differences in height, loads, or soil-bearing capacity, as well as at the junctions of new and old buildings.

Seismic joints: These are designed to make buildings more regular, with the aim of enhancing structural seismic resistance, and the foundation can remain unbroken. The purpose of their installation is to divide large buildings into smaller sections, creating relatively independent seismic units, and to prevent overall structural disharmony and damage due to earthquakes.
 

In seismic defense zones, settlement and expansion joints must meet seismic joint requirements.