I need to level an anhydrite/gypsum-based screed. Do I need a special levelling compound? I need to level an anhydrite/gypsum-based screed. Do I need a special levelling compound?

I need to level an anhydrite/gypsum-based screed. Do I need a special levelling compound?

Due to the risk of reaction and sulphate attack, cementitious materials should not come into direct contact with calcium sulphate-based material, so a priming barrier layer must always be used.

For more information please refer to our guidance note here.

For calcium sulphate screeds that are measured and deemed as dry, below 75% RH, simply follow these simple preparation steps.

Mechanically prepare the surface, removing all laitance, loose debris and dust to expose a sound hard surface.

In most cases ARDEX P 51 Primer, diluted 1:3 with water, can be used to prime the prepared surface, prior to applying any ARDEX Levelling and Smoothing Compound between 3mm to 6mm.

However, some screed manufacturers will specify that an epoxy-based primer is used so please check with the screed manufacturer before selecting the primer.

In this instance apply ARDEX R 3 E Primer and sand blind immediately with ARDEX Fine Aggregate. Once cured remove any excess aggregate and apply any ARDEX DPM 1 C, prior to the application of ARDITEX NA. This system can dramatically speed up the flooring installation process, helping you create the perfect floor in the shortest time possible.

For more information please refer to our guidance note and the relevant product datasheets.

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