The term expansion joint originates from the French word dilatation, meaning to expand or dilate.
An expansion joint profile is a general term used to describe profiles installed within structural gaps—commonly referred to as expansion joints—in buildings, in order to create a flexible zone that accommodates movement during the service life of the structure. Expansion joint profiles consist of profiles fixed to both sides of the structure and the elastic systems positioned between them, enabling the structure to elastically accommodate expansion movements.
In the early years of their use in the construction industry, expansion joints typically consisted of two steel angle profiles filled with elastic filler material. Over time, advancements in manufacturing methods, developments in seismic regulations, and the resulting increase in required expansion joint widths have led to widespread use of aluminum profiles, EPDM seals, soft PVC seals, and thermoplastic elastomer seals. In parallel with improvements in construction materials, the use of stainless steel in expansion joint profiles has also increased significantly.
From the last quarter of the 20th century through the early 21st century, large-scale projects have increasingly occupied extensive footprints. In many cases, high-rise structures are connected to lower-rise buildings. Although expansion joint profiles may not attract the attention of non-engineers or non-architects, they play a critical role today in separating floor, wall, and ceiling finishes in shopping malls, airports, business centers, public buildings, hospitals, and many other projects. They are also widely used in wet areas, terraces, and parking structures, providing comfort and functionality in complex, large-scale buildings.
Expansion joint profiles should not be considered as standalone solutions. In order to meet project requirements before, during, and after construction, they must address the following structural needs:
Accommodating the expansion joint gap with a defined movement capacity
Being compatible with waterproofing systems when required
Withstanding operational loads appropriate to the building’s function (pedestrian traffic, vehicle traffic, forklifts, etc.)
Fully matching adjacent floor and finish heights
Responding to fire protection and fire insulation requirements when necessary
Being compatible and coordinated with the building’s construction method
In general, expansion joint gaps start from a minimum of 30 mm and increase based on whichever is greater: the gap calculated according to seismic regulations or the minimum gap required by structural principles. Depending on the rigidity of the load-bearing system, the type of reinforced concrete structure, the seismic zone of the construction site, and the building height, expansion joint gaps today commonly range from 3.5, 10, 15, 20, 25, 30, to 40 cm. In modern buildings constructed to incorporate seismic isolators, these gaps can sometimes reach 150 to 200 cm.
In such large gaps, steel and rubber articulated systems are typically used. An important consideration is rounding calculated joint gaps up to the nearest practical standard size, taking into account building layout and construction tolerances. For example, if the maximum calculated joint gap is 137 mm, the project engineer will usually round this up to the nearest standard size, such as 150 mm, and design the project accordingly. Otherwise, serious challenges may arise during construction and material procurement.
In multifunctional buildings composed of multiple blocks, certain areas may be used as parking garages, while upper floors may include restaurants, shared restrooms, and circulation corridors. Since each of these spaces has different functional requirements, expansion joint solutions must also vary accordingly. As a result, the use of different expansion joint profiles in different areas of the same project becomes inevitable.
For this reason, during the design phase, project engineers and expansion joint profile manufacturers should collaborate closely to determine the project’s specific requirements. Especially for expansion joint gaps of 100 mm and above, international fire incidents and fire department reports have demonstrated that these joints can create a chimney effect during a fire. Additionally, waterproofing in these areas must be thoroughly evaluated and its continuity ensured, independent of on-site applications.
When selecting expansion joint profiles, finish heights, finish types, corner details, and the intended use of the building must be carefully considered. For example, in industrial facilities, the primary requirement is load-bearing capacity, whereas in healthcare facilities, hygiene and user comfort may be the main priorities. In parking structures, rubber-and-steel or rubber-and-aluminum profiles designed for vehicle traffic and noise reduction are typically preferred.
Once all profile types have been selected, expansion joint profiles are installed progressively in line with the project schedule as finishes are completed.
Another critical factor is the correct selection of bedding materials used to level the expansion joint profile and the anchoring materials used to secure the profile legs to the substrate. Heavy-duty profiles typically require steel anchors or chemical anchors, while epoxy mortar or grout mortar is used as bedding material.
During installation, expansion joint profiles must not bear directly on the joint gap, nor should they be installed as cantilevered elements. If the joint gap exceeds the clear opening capacity of the selected profile, the profile type and size must be revised, and a profile with a larger capacity must be used.
Expansion joint profiles are generally manufactured in lengths of 3 to 4 meters, while seals are produced in continuous lengths of 15 to 25 meters to ensure uninterrupted sealing.
For exterior façade expansion joint profiles, seasonal effects must be taken into account. A minimum expansion gap of 3 mm should be left every three meters along the profile to prevent longitudinal deformation during hot weather.
PVC-based seals should never be used on exterior façades. PVC expands and contracts significantly with temperature changes and becomes rigid in cold conditions. Therefore, thermoplastic-based seals should be used in such applications.
The coefficient of thermal expansion for aluminum is 23 × 10⁻⁶ /°C.
The general thermal expansion formula is:
ΔL = L × (T₂ − T₁) × C
Where:
L = profile length
C = coefficient of thermal expansion
T₂ = maximum temperature
T₁ = minimum temperature
For example, in a location where the temperature ranges from −5 °C in winter to +37 °C in summer:
ΔL = 3000 × (37 − (−5)) × 23 × 10⁻⁶
ΔL ≈ 2.89 mm ≈ 3.00 mm
It is our hope that this article serves as a comprehensive and informative overview of expansion joint profiles. In our next article, we will focus on fire protection solutions and insulation methods for expansion joints.