General requirements for the base layers

As a general rule and as part of their requirement to carry out an inspection and due diligence, the contractor for flooring work or the private individual laying their own flooring must be reasonably satisfied that the base is ready for laying before the flooring is laid. The following points in particular must be taken into account when assessing whether these floors are ready to be laid. Failure to comply with these will render any claims under the guarantee or warranty void.

CHECKING THE MOISTURE LEVEL IN THE BASE LAYER:

The test is conducted using a CM device. The following limit values must not be exceeded:

• For cement screeds ≤ 2 CM % – heated screeds ≤ 1.8 CM %

• For calcium sulphate screeds / calcium sulphate flowing screeds ≤ 0.5 CM % – heated screeds ≤ 0.3 CM % These values apply to screeds that do not have any admixtures. When using admixtures or fast-drying screeds, the measurements and limits specified by the respective manufacturer must be observed. The test sample must be taken from the lower third of the screed. The thickness of the screed must also be measured and recorded.

CHECKING THAT THE BASE LAYER IS EVEN:

Refer to the current standards when checking that the base layer is even. To do this, place a measuring rod or straight edge on the highest points of the surface. This is how you determine the depth at the deepest point in relation to the supporting surfaces (measurement intervals). With a measurement interval of 180 cm, the vertical deviation must not exceed 3 mm. Larger deviations should be compensated for by taking appropriate action, e.g. by using self-levelling compounds.

Air humidity in % Living area climate over the year

Too humid

Ideal value 35-60 %

Too dry

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Please take care not to exceed or fall below the ideal humidity value shown in the diagram over the course of the year.

CHECKING THE LOAD BEARING CAPACITY OF THE BASE LAYER:

The base layer must be a closed self-supporting layer.

CHECKING THAT THE BASE LAYER IS CLEAN:

The base layer must have been vacuumed beforehand.

CHECKING THE AMBIENT CLIMATIC CONDITIONS:

The following conditions must be met before, during and after installation:

• an indoor room temperature of at least 18 °C

• a ground surface temperature of at least 15 °C

• relative humidity between 35 % – 60 % When laying floors using a floating installation, any of the base layers can be used if they meet the requirements listed above. This includes in particular:

• all types of screed, including hot water-based heating screeds

• Chipboard constructions

• Fibreboard

• Existing floor coverings such as PVC, linoleum, natural stone slabs and ceramic tiles

Unsuitable base layers:

As a general rule, designer flooring may only be installed on solid, non-floating base layers. Failure to comply with these will render any claims under the guarantee or warranty void.

Ideal temperature

The maximum surface temperature of 60 °C for SPC flooring and of 32 °C for vinyl flooring must not be exceeded. In addition, a very rapid heating sequence must be avoided.

PLEASE NOTE

In each case, temperatures in the area of the installed surface must be typical for living areas throughout the year.

We recommend heating the affected rooms in winter and protecting them from direct sunlight or darkening them in summer by taking appropriate precautions (e.g. roller blinds or venetian blinds).

If these recommendations and regulations are not complied with, any guarantee or warranty claims on the part of HWZI are excluded. Accordingly, prior to the installation of a systemrelated insulation underlay, all screeds (with the exception of mastic asphalt) must have (see point: Caution! underlay materials) a moisture protection foil SD value ≥ 75 m must be installed as a vapour barrier over the entire surface and in the form of a tray, if the underlay mat does not offer an equivalent function. When properly installed by a professional, the sheets of moisture protection film must overlap by 5 - 20 cm in the joint area, depending on the design. If no underlay mat is being used, the moisture protection foil should still be used for decoupling under the designer flooring.

Screeds with hot water underfloor heating

When installing a heated floor construction, all parties involved (builder, architect, heating planner, heating contractor, installer, flooring manufacturer) must work in coordination with each other. Every surface-heated floor requires use-related planning and coordination with regard to the heating system and the screed. This is to ensure that there is no damage and the best possible functionality over the long term. In addition to the usual tests of the installation's base layer, the underfloor heating or cooling system must be tested for functionality (functional heating or cooling). This proof of proper heating and cooling of the screed construction must be provided at all times of the year and documented in a heating and cooling log.

DIN EN 1264-2

EN 1264-2 specifies the framework conditions and the test for determining the performance of hot water underfloor heating systems as a function of the difference between the heating medium temperature and the room temperature. The heat output is checked by calculation and by taking measurements.

The following are regarded as base layers with limited suitability:

• Electrically operated underfloor heating systems (controlled surface temperature)

Electric underfloor heating systems are classified as base layers with limited suitability. This is because a number of foil-based, electric heating systems can generate surface temperatures much higher than 28 °C. Approval will be given for an electrically operated underfloor heating system: If this can be controlled digitally and there is a guarantee that the surface temperature never exceeds 28° C. In addition, technical approval for designer floors must be given by the manufacturer of the heating system. There is NO guarantee for products that are installed on infrared underfloor heating.

Screeds / concrete bases

When laying floating designer flooring on screeds, please note that rising damp must be expected.

When heating the load or heat distribution layer, a distinction is made between functional heating and heating for readiness for covering.

• The functional heating is the heating contractor's proof of the provision of non-defective workmanship. It also serves to check the functional efficiency of the heated floor construction.

• Heating for readiness for covering is the process of driving out the residual moisture in the screed until it is ready for covering.

Natural stone and ceramic tiles

Residual moisture must be expected to rise and, accordingly, before the system-related insulation underlay (see point: Caution! underlay materials) a moisture protection foil SD value ≥ 75 m must be installed as a vapour barrier over the entire surface and in the form of a tray. If footstep soundproofing is laminated on the back of the design floor, you must not lay any further insulation underlay.

OSB, chipboard and fibreboard

To improve the footstep soundproofing, lay a system-appropriate insulating underlay before installing designer flooring (see point: Caution! underlay materials). If no underlay mat is being used or if you are installing a floor covering with an integrated underlay mat, a 0.2 mm PE construction foil should be installed for decoupling purposes.

Wooden floorboards

Any loose panels should be properly screwed in place. To improve the footstep soundproofing, lay system-appropriate insulation underlay before installing the designer flooring (see point: Caution! underlay materials). If no underlay mat is being used or if you are installing a floor covering with an integrated underlay mat, a 0.2 mm PE construction foil should be installed for decoupling purposes.

Elastic floor coverings (PVC, linoleum, vinyl)

These floor coverings do not require a moisture protection film. As this elastic floor covering acts in the same way as the vapour barrier. To improve the footstep soundproofing, lay a system-related insulation underlay before installing the designer flooring. Designer flooring with an underlay mat laminated to the back can be laid directly onto the elastic floor covering. (see point: Caution! underlay materials)

Wet rooms / damp rooms

You can even install designer flooring in damp rooms – with the exception of saunas. Failure to comply with these will render any claims under the guarantee or warranty void.

DIN 18365

The DIN 18365 standard for "floor covering work" applies to the laying of floor coverings in sheets and tiles made of linoleum, plastic, elastomer, textiles and cork as well as to the laying of multi-layer elements.

PLEASE NOTE

Functional heating does not ensure that the screed has reached the residual moisture required for readiness for covering. As a result, heating to readiness for covering is usually required.