Expansion joints – what are they? When are they used?

During a renovation involving floor replacement, you may have heard the term ‘expansion joint’, but it doesn’t mean much to you? Or perhaps someone mentioned a ‘moving floor’? And you’re wondering how it’s possible for a floor to move? An expansion joint is a concept closely linked to various fields of construction and interior finishing. There are various types, but this time we’ll focus on expansion joints in the context of floor finishing. In this article, you’ll learn, amongst other things, why and where expansion joints are used, as well as how to conceal them.

What is an expansion joint?

The general definition of an expansion joint states that it is a deliberately created gap located between two adjacent structures or individual elements thereof. This makes them more resistant to deformation or the effects of loads that may be caused by various external factors. Expansion joints between individual structural elements of buildings help to prevent stresses and deformations in materials, for example as a result of uneven settlement. 

Factors that can influence the deformation of building components, as well as the materials from which they are made, include, amongst others: air temperature and humidity. 

You may come across various types of expansion joints in your daily life, not just in your own home. There are, in fact, several types of such solutions:

structural expansion joints – these are most commonly used for individual structural elements of a building to avoid stresses associated with the building’s statics. Examples include situations where further elements, known as extensions, are added to an existing structure;

thermal expansion joints – these are used where fluctuating temperatures may affect the dimensions of the material used. They reduce the risk of stress and warping in individual structural elements. Railway tracks are a perfect example of this. Next time you’re travelling by train and hear that characteristic clattering sound, it’s most likely because the train’s wheels have hit a gap in the rails. This gap is there to prevent the track from deforming as a result of the metal components expanding, thereby preventing the train from derailing;

technological expansion joints – these are installed to prevent deformation of the materials already used to construct specific elements of a building, including certain materials used for interior finishes. Concrete screeds are a good example here;

anti-vibration expansion joints – these are designed to eliminate the effects of various types of vibrations and shocks that could cause damage to buildings. They are usually associated with buildings constructed in regions at risk of earthquakes. However, you may also find them in buildings constructed near mines. They are also used in production halls where large machines that generate strong vibrations are installed.

Why is an expansion joint incorporated into the floor’s finishing layer?

In the case of flooring, the external factors mentioned above – including temperature and air humidity – cause the material to shrink or swell. It is precisely this swelling and shrinking of the material from which the floor is made that is commonly referred to as a ‘working floor’.

Floor expansion joints are installed at both the structural and finishing stages. It is recommended to install expansion joints for virtually every type of floor and its finish. An additional factor that necessitates the creation of expansion joints is the use of underfloor heating in a given room. This is because, under the influence of heat, many of the materials used to make floors begin to ‘expand and contract’.

It is also recommended to install expansion joints in rooms with large floor areas. However, this is not usually necessary in standard residential rooms. Bear in mind that floor expansion joints should be installed not only indoors, but also in areas such as terraces and balconies.

Bear in mind that a properly installed expansion joint will not only affect the durability of the materials and the floor itself, but also its appearance. This will minimise, for example, the risk of ceramic tiles cracking or chipping, as well as scratches on walls or bulging of the material in the case of laminate flooring or floorboards. In the case of laminate flooring, the locking mechanisms may also break. Failure to install expansion joints, or installing them incorrectly, can therefore lead to the destruction of certain parts of the floor. In extreme cases, this may necessitate replacing the entire floor with a new one.

Rules for correct floor installation – what expansion joints should be provided?

Note that an expansion joint is most commonly installed around the perimeter of the floor, i.e. where it meets the wall, as well as at door openings. It is worth noting, however, that for very large areas, expansion joints should also be installed to divide the floor surface into smaller sections that can move independently of one another. This will reduce the risk of stress building up in the centre of the surface. Usually, the manufacturer specifies the minimum area above which additional expansion joints are required.

The method of installing the expansion joints will depend on the type of flooring material and the manufacturer’s recommendations. The perimeter expansion gap should be approximately 10 mm. This recommendation applies to most types of flooring materials, particularly laminate or vinyl flooring. An example of this is Vilo rigid-core vinyl panels. Please note, however, that using other materials or finishing a larger area may require this gap to be increased. Also bear in mind that the perimeter expansion gap left for the panels should not be filled with anything (see below for information on how to conceal it). The situation is different for screeds or walls, where expansion gaps require special filling.

The air temperature during panel installation is also important. If you wish to minimise the risk of warping as the floor settles, follow the manufacturer’s instructions carefully. For laminate and vinyl panels, it is recommended that installation be carried out at a temperature of between 15 and 24 degrees Celsius.

How do you conceal an expansion joint?

Skirting boards designed to conceal expansion gaps help to create a neat finish where the wall meets the floor. They are available in a wide range of options, including different colours, milling styles and patterns. Here you’ll find the range of skirting boards from the Vilo brand. This allows you to match them perfectly to both the colour of the floor and other elements in the room. So don’t worry about expansion gaps. Install them so that you can enjoy a floor for many years to come, one that will retain its properties despite the changing conditions inside your house or flat.