Expansion Joints, Settlement Joints, Seismic Joints, Do You Know The Difference?

Expansion joints, settlement joints, seismic joints: collectively known as deformation joints.

What is a deformation joint?

Due to the change of temperature, uneven foundation and seismic factors, the building is easy to deformation or damage, so the design should be divided into a number of independent parts of the house, so that each part can be free of independent changes. The building will be vertically separated from the reserved joints called deformation joints, including expansion joints, settlement joints, seismic joints.


Explanation of terms

Expansion joints: When the building is long, the deformation joints are set to avoid the cracks of structural members due to thermal expansion and contraction of the building.

When joints are needed

  1. The length of the building exceeds a certain limit.
  2. complex and varied building plan.
  3. The type of structure in the building is highly variable.

setting principles

The expansion joints are usually installed by leaving a gap vertically at intervals along the length of the building or at large structural changes, with all the building components above the foundation broken off and divided into separate parts that can expand and contract horizontally. The foundation part is less affected by temperature changes, and generally does not need to be disconnected.

the distance between the joints

The maximum spacing of expansion joints should be determined according to the structure of different materials, see Design Code for Concrete Structures (2002). p112 Table 9.1.1 lists the maximum spacing of expansion joints for masonry and reinforced concrete houses respectively.

construction of the joints

The width of the expansion joint is generally 20-40mm, usually 30mm.

Other requirements

In terms of structural treatment, the brick and concrete structure can adopt single-wall or double-wall scheme; the frame structure can adopt double-column and double-beam scheme or pick-up beam scheme.

  1. Wall expansion joint structure.

Wall expansion joints are generally made in the form of flat joints, when the thickness of the wall is more than 240mm, can also be made in the form of staggered joints, mouth joints and other forms.

Outer wall deformation joints commonly used hemp asphalt, foam strips, grease and other elastic waterproof material caulking, the seam with galvanized iron, color sheet steel and other materials to cover the seam treatment; inner wall deformation joints are generally combined with interior decoration with wood, various types of metal panels and other cover seams.

  1. floor expansion structure.

The floor expansion joints of the joints commonly used in hemp asphalt, foam strips, oil paste and other caulking for sealing treatment, topped with metal, concrete or rubber and other activities such as cover plate. The structure treatment needs to meet the use requirements such as flat, smooth, waterproof and sanitary ground.


The roof expansion joint should be combined with interior decoration, generally using metal, wood or rubber and plastic panels to cover the joints, and the cover joint plate can only be fixed on one side to ensure that the two sides of the components can be free to expand and deform in the horizontal direction.

  1. Roof expansion joints construction.

There are two kinds of expansion joints on the roof, one at the same elevation on both sides of the roof and the other at the staggered elevation on both sides of the roof, when the two sides of the expansion joints have the same roof elevation and the upper roof, they are usually waterproofed with ointment caulking and flooding treatment; when it is not the upper roof, they are added on both sides of the seam to build half a brick dwarf walls, respectively, roof waterproofing and flooding treatment, the requirements of which are the same as roof waterproofing and flooding structure. On the top of the short wall, the traditional practice of galvanized iron cover seam, in recent years gradually popular with color plate, aluminum and even stainless steel cover seam.

Expansion Joints, Settlement Joints, Seismic Joints, Do You Know The Difference?

settlement joints

Explanation of terms

Settlement joints: The deformation joints are set to prevent uneven settlement of the building due to the different bearing capacity of the foundation or the large difference in load of each part of the building, resulting in the destruction of the building.

the need to set up joints

  1. When the building is built on different foundations and it is difficult to ensure uniform settlement.
  2. When the foundation form, width and depth of burial of the adjacent parts of the same building differ significantly from each other, it is easy to form uneven settlement.
  3. When the height difference between adjacent parts of the same building is large (generally more than 10 m), the load difference is large, or the structural form varies considerably, etc., which may lead to uneven settlement.
  4. When the shape of the plane is complex and the connecting parts of the parts are weak.

Between the original building and the new or expanded building.

The principle of installation

When setting up settlement joints, the foundation, walls, floors and roofs of the building must be disconnected in the vertical direction, so that each part can form an independent rigidity unit that can settle freely.

the structure of the joints

Settlement joints can double as expansion joints. The width of settlement joints is related to the foundation condition and building height.

  1. foundation structure treatment of settlement joints: settlement joints of the foundation should also be disconnected, the structural treatment of the two cases of brick and concrete structure and frame structure, brick and concrete structure under the wall strip foundation usually have double wall eccentric foundation, beam foundation, column cross layout and other three forms of treatment.
  2. wall, floor, roof settlement joints structure: wall settlement joints commonly used galvanized iron, aluminum alloy plate and color thin steel plate cover joints; ground, floor layer, roof settlement joints cover joints treatment with the basic expansion joint structure. The treatment of roof cover seam should fully consider the deformation direction to minimize the influence of uneven settlement.

Anti-vibration joints

In areas where the seismic intensity is between 7 and 9 degrees, seismic seams are required when one of the following conditions applies.


  1. The difference in elevation of the adjacent house is greater than 6m.


  1. The house has misshapen floors and a large difference in floor level.


  1. The stiffness and quality of the structure adjacent to the house are very different.


The width of the anti-seismic joints is generally 50-100 mm, but for multi-storey and high-rise reinforced concrete structure houses, the minimum width of the joints should meet the following requirements.

  1. When the height does not exceed 15m, the seam width is 70mm.
  2. When the height exceeds 15m, the width of the slit shall be increased according to different fortification intensities.

(1). In areas of 6 degrees, the width of the joints increases by 20 mm for every 5 m of building height.

(2).In areas of 7 degrees, the width of the joints increases by 20 mm for every 4 m of building height.

(4).In areas of 8 degrees, the width of the joints increases by 20 mm for every 3 m of building height.

(5).In the area of 9 degrees, the width of the joints shall be increased by 20mm for every 2m increase in the height of the building.

Anti-vibration joints should be set along the full height of the building. Generally, the foundations can not be separated, but when the plane is more complicated, the foundations should also be separated.

Double walls or columns should generally be arranged on both sides of the seam to strengthen the overall rigidity of the houses on both sides of the seismic joints.

The structure of the seismic joints on the walls, floors and roof is basically the same as that of the settlement joints. In addition, it should be noted that the seismic joints should not be made into staggered openings or openings, thus losing their function.