Levelling Over Epoxy Flooring: Getting the Substrate Right
Levelling Over Epoxy Flooring: Getting the Substrate Right
Levelling over epoxy-coated floors or preparing substrates for new epoxy coatings is a high-visibility task. Unlike many other floor coverings, epoxy will faithfully mirror whatever is underneath – every ripple, scratch and crack.
In this article, ARDEX Technical Services Advisor John Werlemann explains what makes levelling over epoxy different, the importance of concrete surface profile, and how to choose suitable levelling compounds.
Why epoxy shows everything
With many finishes – such as carpet or some resilient coverings – minor imperfections in the substrate are hidden from view. Epoxy systems are different:
– They form hard, thin films or toppings that closely follow the profile of the substrate.
– Any imperfections, such as cracks, grinding marks or contamination, are magnified rather than concealed.
This means that substrate preparation is critical. If you are levelling beneath an epoxy coating, the standard of preparation and levelling must be significantly higher than for many other coverings.
Achieving the right concrete surface profile (CSP)
ARDEX system recommendations and technical bulletins typically call for substrates to be prepared to CSP 3 (Concrete Surface Profile 3) for epoxy work. This is usually achieved by:
– Carrying out a light grind to remove contaminants, laitance and surface weak layers.
– Exposing a clean, sound surface with a uniform profile.
– Revealing any existing cracks or defects that need repair.
This step not only improves adhesion but also gives the installer a clear view of issues that must be addressed before levelling and epoxy application.
Selecting suitable levelling compounds
Not all levelling compounds are suitable beneath epoxy. Products must be:
– Strong enough to withstand the hardness and tension of the epoxy layer.
– Resistant to indentation and marking under service loads.
– Compatible with the epoxy system in terms of moisture and curing characteristics.
In general, you should look for high-strength levelling compounds that are recommended by ARDEX specifically for use under epoxy coatings. These will provide a dense, stable substrate that won’t deform or powder under load.
The role of substrate preparation
Surface preparation remains the number-one factor in successful epoxy flooring:
– Any cracks must be identified and treated with appropriate repair products.
– Contaminants such as oils, paints and adhesives must be fully removed.
– The entire surface must be clean, dry and structurally sound before levelling and epoxy application.
If defects are left untreated, they will almost certainly show through the epoxy and can lead to premature failure of the coating.
Consequences of poor preparation or wrong leveller
If the substrate is not prepared properly, or if an unsuitable levelling compound is used under epoxy, a range of problems can occur:
– Cracks in the substrate can reflect through the levelling layer and into the epoxy coating.
– Soft or weak levellers may become indented or marked, which the epoxy will then highlight.
– Poor bond between layers can lead to peeling or delamination of the epoxy.
Because epoxy finishes are so visually revealing, these defects are immediately obvious to clients and are often costly to rectify.
Choosing the right ARDEX system
To select an appropriate system for levelling beneath epoxy:
– Refer to ARDEX system recommendation documents and technical bulletins for epoxy flooring.
– Check individual product datasheets for suitability under epoxy and for recommended preparation and priming methods.
– Contact the ARDEX Technical Services hotline if you have any doubts about product selection or methodology.
Taking the time to confirm the system up front helps ensure that the epoxy floor looks as good as the client expects – and stays that way.
Key points when levelling under epoxy
For best results:
– Treat substrate preparation as non-negotiable – achieve at least CSP 3 via light grinding.
– Repair cracks and defects before levelling.
– Choose high-strength, epoxy-compatible levelling compounds.
– Remember that whatever you leave in the substrate will be visible and magnified through the epoxy.
With proper preparation and product selection, levelling over epoxy-coated floors – or preparing for new epoxy systems – can deliver clean, high-spec finishes that stand up to scrutiny.
ARDEX Technical Hotline: 1800 224 070
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