Screed Thickness | Minimum And Maximum Thickness According To DIN

Screed Thickness | Minimum And Maximum Thickness According To DIN

Screed is an important building element that has a variety of functions. In living areas, screed is mainly used as a subfloor for floor coverings and as an intermediate layer for pipes or underfloor heating. When processing the floor, a distinction is made between different construction methods, but they have one thing in common: standardized thicknesses. The screed thickness is specified in order to be able to guarantee the load-bearing capacity under load.

When laying screed, numerous points must be observed. Since the screed is an important floor layer in living spaces, you must lay it precisely to counteract a phase shift. An essential value is the screed thickness, which is regulated according to the ISO standard DIN 18560. It sets out the nominal minimum and maximum thicknesses that the installer and you will consult when laying screed. These guarantee the functionality of the screed ceiling and ensure that, for example, the underfloor heating can provide the desired heat. The use of standardized thicknesses is a must, especially in living rooms, so that you can pursue your function.

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important values

Since screed thicknesses are standardized, the information is given in specific values ​​that help with implementation. These would be:

1. Screed type: the screed type indicates the type of screed. This information is important because each of the six types of screed is effective in different thicknesses, which makes a distinction necessary. These are abbreviated, for example CAF stands for calcium sulphate floor screed.

2. Flexural strength class (also known as hardness class): this specification describes the respective flexural strength class of the screed types. The screed type alone is not enough to be able to determine the screed thickness, because each type has several hardness classes that determine the respective tensile stress under load. These are specified with a number and a letter (F and C) and are defined by the DIN EN 13813 standard.

3. Minimum nominal thickness: the minimum nominal thickness is specified in mm and describes the minimum height that a screed layer must have. These are fully standardized and must be complied with.

4. Maximum thickness: the maximum thickness of the floor screed is also given in mm and is only specified in a few cases by the standard, as you can see from the list below. When building a house, a maximum thickness of 5.5 to 8 cm is usual, but this value can vary greatly with the exception of the standardized units, which is something you absolutely have to watch out for.

5. Compressibility: the compressibility is given in c and for residential areas it has a value of up to or equal to 5 mm, which is used in the list below. An exception is the mastic asphalt screed, which has a compressibility of up to or equal to 3 mm. This value describes the difference between the delivered thickness and the thickness under load of the impact sound insulation that is laid under the screed and has to withstand a lot.

6. Area load: the area load is applied to vertical payloads acting on the ground. This means, for example, human movements that occur normally throughout the day. In construction there are several area loads that must be taken into account. For living spaces, a distributed load of up to or equal to 2 kilonewtons (kN) per square meter is specified, which is used for all thicknesses in the list below.

Tip: no screed thicknesses for heavy-duty screeds, i.e. industrial screeds, are listed here. These are never used in your own four walls or in the hobby area and are therefore unimportant for you.

Screed thickness: an overview

Calcium sulphate floor screed (CAF)

The following are the thicknesses for floating screeds on insulation layers:

  • F4: Minimum nominal thickness up to or equal to 35 mm, no maximum thickness
  • F5: Minimum nominal thickness up to or equal to 35 mm, no maximum thickness
  • F7: Minimum nominal thickness up to or equal to 35 mm, no maximum thickness

Calcium sulphate screed (CA)

The following are the thicknesses for floating screeds on insulation layers:

  • F4: Minimum nominal thickness up to or equal to 45mm, no maximum thickness
  • F5: Minimum nominal thickness up to or equal to 40 mm, no maximum thickness
  • F7: Minimum nominal thickness up to or equal to 35 mm, no maximum thickness

The minimum nominal thickness for screeds on separating layers is a maximum of 30 mm.

Mastic asphalt screed (AS)

The following are the thicknesses for floating screeds on insulation layers:

  • IC10: Minimum nominal thickness up to or equal to 25 mm, no maximum thickness

The minimum nominal thickness for screeds on separating layers is a maximum of 25 mm.

Synthetic resin screed (SR)

The following are the thicknesses for floating screeds on insulation layers:

  • F7: Minimum nominal thickness up to or equal to 35 mm, no maximum thickness
  • F10: Minimum nominal thickness up to or equal to 30mm, no maximum thickness

The minimum nominal thickness for screeds on separating layers is a maximum of 15 mm.

Magnesia screed (MS)

The following are the thicknesses for floating screeds on insulation layers:

  • F4: Minimum nominal thickness up to or equal to 45mm, no maximum thickness
  • F5: Minimum nominal thickness up to or equal to 40 mm, no maximum thickness
  • F7: Minimum nominal thickness up to or equal to 35 mm, no maximum thickness

The minimum nominal thickness for screeds on separating layers is a maximum of 30 mm.

cement screed (CT)

The following are the thicknesses for floating screeds on insulation layers:

  • F4: Minimum nominal thickness up to or equal to 45mm, no maximum thickness
  • F5: Minimum nominal thickness up to or equal to 40 mm, no maximum thickness

The minimum nominal thickness for screeds on separating layers is a maximum of 45 mm.

bonded screeds

Bonded screeds are standardized as the only screeds with a maximum thickness. The reason for this is the application, because the screed is applied directly to the unfinished floor in comparison to the other types. This has a corresponding effect on the screed thickness. Following the values:

  • Calcium sulphate screed: no minimum nominal thickness, maximum thickness up to 50 mm
  • Mastic asphalt screed: no minimum nominal thickness, maximum thickness up to 40 m
  • Synthetic resin screed: no minimum nominal thickness, maximum thickness up to 50 mm
  • Magnesia screed: no minimum nominal thickness, maximum thickness up to 50 mm
  • Cement screed: no minimum nominal thickness, maximum thickness up to 50 mm