oSIST prEN 1937:2026

oSIST prEN 1937:2026 is the Slovenian adoption of draft European Standard prEN 1937:2026 from CEN, prepared by CEN/TC 193 “Adhesives”. It specifies a standard way to mix cementitious and calcium sulfate-based floor levelling compounds with water and/or a liquid component supplied by the manufacturer, so test mixes are prepared the same way for laboratories, manufacturers and other users.

What does oSIST prEN 1937:2026 specify?

oSIST prEN 1937:2026 specifies the procedure for mixing cementitious and calcium sulfate-based floor levelling compounds and the conditions needed to make that mixing repeatable. It covers the method, the apparatus, the materials, the conditioning of test items and the information that must be reported after mixing.

The document applies to compounds used to prepare subfloors before floor coverings are installed. In practice, it matters because the mixing step affects the homogeneity, absorbency, evenness and strength of the prepared layer that is later tested or used.

The document is organized into these main clauses:

• Clause 1 - Scope
• Clause 2 - Normative references
• Clause 3 - Terms and definitions
• Clause 4 - Apparatus
• Clause 5 - Materials
• Clause 6 - Mixing conditions
• Clause 7 - Mixing procedures
• Clause 8 - Test report

What are the key requirements of oSIST prEN 1937:2026?

oSIST prEN 1937:2026 is mainly about controlling the mixer, the sample condition and the timing of the mix. Those controls are what make test results comparable from one laboratory to another.

• Clause 4 requires a mixer in accordance with EN 196-1, with a stainless steel bowl of about 5 l and a stainless steel blade of the stated shape and movement. The bowl and blade are used as a set, and the blade-to-bowl gap must be checked monthly. In practice, this reduces variation caused by different mixer geometries.
• Clause 4 also sets the blade speeds for low and high speed. This means the mixer settings are part of the method, not just laboratory preference.
• Clause 5.1 requires sampling of the powder component in accordance with EN ISO 15605 and preparation for testing in accordance with EN 1067, then storage in a dry sealed container. In practice, the sample must stay representative and protected until mixing starts.
• Clause 5.2 says the liquid component is water and/or a separate liquid component supplied by the manufacturer, and the water shall be distilled or deionized unless another water can be shown to give the same results. This matters when a lab wants comparable results across test series.
• Clause 6 requires all test materials to be conditioned for at least 24 h at 23 ± 2 °C and 50 ± 5 % relative humidity, and the test room air circulation must not exceed 0.2 m/s. In practice, temperature and humidity must be stable before mixing begins.
• Clause 7 gives two mixing routes: one without waiting time and one with waiting time if the manufacturer requires it. The no-wait procedure uses 2 kg powder component, low-speed mixing, scraping of the vessel, and a total mixing time of not more than 3 min; the mixture must be free from air bubbles or be deaerated for 1 more minute before use. The waiting-time procedure adds a waiting period, further low-speed mixing and a deaeration step.
• Clause 8 requires the test report to state which mixing procedure was used and the total time elapsed to the end of mixing. In practice, this lets later tests be traced back to the exact preparation route.

What terms does oSIST prEN 1937:2026 define?

oSIST prEN 1937:2026 uses a small set of terms to describe the product and the prepared mix.

• Underlayment - a thin layer on a load-bearing substrate that provides a smooth and/or flat surface for floorings and has a uniformly absorbent surface.
• Cementitious-based floor levelling compound - a ready-mixed dry mortar whose binder consists mainly of cement and/or cementitious binders.
• Calcium sulfate-based floor levelling compound - a ready-mixed dry mortar whose binder consists mainly of calcium sulfate.
• Powder component - the floor levelling compound before liquid is added.
• Prepared component mixture - the compound after it has been mixed with a liquid component such as water.
• Set component - the prepared component mixture after it has set.

Who uses oSIST prEN 1937:2026?

oSIST prEN 1937:2026 is used by testing laboratories, manufacturers of floor levelling compounds, and technical or quality staff who prepare samples and run product tests. It is also relevant for specification writers and buyers who need a common laboratory mixing method when comparing products. The standard supports routine testing, product development, quality control and the documentation of test conditions.

What changed in oSIST prEN 1937:2026 from the previous edition?

oSIST prEN 1937:2026 supersedes EN 1937:1999. The foreword states these significant technical changes:

• the older term “hydraulic setting floor smoothing and/or levelling compounds” was replaced with “cementitious and calciumsulfate-based floor levelling compounds”
• the scope was made more specific
• the terms “underlayment”, “cementitious-based floor levelling compound” and “calcium sulfate-based floor levelling compound” were added
• the mixing speed was updated in the mixing procedure
• editorial changes were made

Which standards are used with oSIST prEN 1937:2026?

• EN 196-1 - provides the mixer arrangement used in the apparatus clause.
• EN 923 - supplies adhesive terms and definitions used in Clause 3.
• EN ISO 15605 - gives the sampling method for the powder component.
• EN 1067 - covers examination and preparation of samples for testing.
• EN 13318:2025 - supplies screed material and floor screed definitions used alongside the terms in this document.
• ISO 554 - specifies the standard atmospheres used for conditioning and testing.

What does the oSIST prEN 1937:2026 document contain?

oSIST prEN 1937:2026 contains a drawing of the bowl and blade and a table of mixer speeds, so users can set up the apparatus the same way. It also gives the material handling steps for the powder and liquid components, including storage and conditioning before testing. The mixing procedures are written as practical laboratory steps for preparing a test mix with or without waiting time.

The final clause on the test report tells users what to record after mixing. That makes the method suitable for later performance testing, comparison of products and traceable laboratory records.