This is what we talk about: the thickness of the screed for underfloor heating

If you want to learn about the optimal thickness for underfloor heating screed, read the following blog post. Discover the role of screed thickness and why it is crucial for efficient underfloor heating. Also, find out what type of screed is best and what the minimum and maximum thickness of the screed can be. Happy reading!

What is Underfloor Heating Screed?

Underfloor heating screed is a layer of concrete or anhydrite used to level and cover the underfloor heating system before laying the floor finish. Concrete screed is made from a mixture of cement, sand, and water, which is leveled and spread on the floor. Anhydrite screed, on the other hand, is made from dehydrated gypsum.

Underfloor heating is a popular heating method because it provides uniform and comfortable heating in the room. Screed is essential for the proper operation of the underfloor heating system because it ensures adequate heat distribution across the entire floor surface. Additionally, screed also serves a protective function, protecting the pipes of the underfloor heating system from damage and providing durability and strength to the floor. Underfloor heating screed should be carefully executed and adequately protected from moisture absorption from the substrate to avoid problems related to moisture and mold.

What Role Does Screed Play in Underfloor Heating?

Screed in underfloor heating performs very important functions. Firstly, it serves as a base, more specifically, a fixing element for pipes and heating elements installed in the floor. Thus, the screed creates a solid and stable foundation for the heating system. Secondly, the screed is intended to evenly distribute heat across the entire floor surface. This ensures uniform heating of the room without temperature differences in different parts of the floor.

Additionally, the screed also acts as a protective layer for pipes and other heating system elements against mechanical damage such as impacts or overloads. The screed should be properly selected and executed to perform its tasks efficiently and reliably. Therefore, it is important to entrust its execution to specialists with experience in underfloor heating installation.

What is the Best Underfloor Heating Screed?

Screed in underfloor heating is one of its key components (besides pipes, through which heat is distributed, underfloor heating manifold, and heat source). It is the screed that allows for the solid and stable embedding of installation pipes, which are the main elements of the underfloor heating system. The screed also aims to ensure even heat distribution across the entire floor surface. Depending on preferences and needs, there are two main types of screed used in underfloor heating.

The first one is cement screed, which is characterized by high mechanical strength, ensuring long-lasting and stable operation of the heating system. The second type is anhydrite screed, which is less popular but has its advantages, which will be discussed below.

Anhydrite screed is characterized by fast setting and the ability to be used in very thin layers. In recent years, anhydrite screeds have been gaining popularity because they are self-leveling screeds, which are characterized by ease of use and precision. Thanks to them, achieving a perfectly smooth floor surface becomes much easier and faster.

Additionally, there is also the possibility of using anhydrite screed with the addition of fibers, which makes it even more durable and resistant to cracking.

What Thickness of Underfloor Heating Screed Will Be Best?

Properly choosing the thickness of underfloor heating screed is important for achieving optimal heating capabilities. It should be remembered that concrete screeds conduct heat worse than anhydrite screeds. Therefore, it is important to choose the appropriate thickness that will ensure efficient and uniform floor heating. Too thin a screed may not provide sufficient strength, resulting in cracking.

On the other hand, too thick a screed can lead to longer floor heating times. Therefore, it is important to consult with a professional when choosing the thickness of the screed to match it to the type of floor, heat source, and conditions in the room. This allows for achieving optimal underfloor heating capabilities and thermal comfort in the room.

Minimum Thickness of Underfloor Heating Screed

The minimum thickness of underfloor heating screed depends on the type of screed used. In the case of concrete screed, the minimum thickness is 6-7 cm. This is due to the need to properly protect the pipes and underfloor installations and to ensure proper heat distribution across the floor surface.

On the other hand, for anhydrite screed, the minimum thickness should be at least 3.5 cm. Anhydrite screed is characterized by lower density and greater fluidity than concrete, which is associated with its specific properties. Regardless of the type of screed, it is important for its thickness to be adapted to the specific characteristics of the room and the technical and design requirements. It should be remembered that the proper thickness of underfloor heating screed ensures not only the proper functioning of the underfloor heating but also the durability and strength of the entire structure.

It should be noted that ultimately, the thickness of the screed must be decided by the contractor, who is familiar with the building and the basic assumptions of the underfloor heating in a given location, and our indications are for reference only.

Maximum Thickness of Underfloor Heating Screed

The maximum thickness of underfloor heating screed is significant both for heating efficiency and for construction costs. In practice, it is best to use a concrete screed with a maximum thickness of 8-10 cm. This value should not be exceeded for several reasons. Firstly, the high cost of concrete requires careful calculation of the costs of the material itself, which will be used for the screed. The thickness of the screed should be well thought out to avoid unnecessary expenses. Secondly, the efficiency of heat transfer is better with a thinner concrete layer, which means faster and more uniform heating of the room.

On the other hand, anhydrite screed, which is popular due to its self-leveling properties, should not exceed a maximum thickness of 9 cm. Above this value, there is a risk that its heat transfer capabilities will be insufficient. Therefore, when choosing the thickness of underfloor heating screed, both the material from which the screed is made, the total costs of its execution, and the optimal thermal efficiency we want to achieve should be taken into account.
It should also be remembered that the thicker the screed, the greater the inertia (i.e., inertia) of the underfloor heating. This means that potentially, the floor heating may take longer to heat up in the event of starting a cold system (e.g., after a heating break). Therefore, there seems to be no special reason to overdo the thickness of the screed - on the contrary, the aim should be to achieve an optimal thickness, and the principle of "the more, the better" does not apply here.