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When you read the technical documentation of an epoxy coating system, you will come across figures such as a 50µm primer coat, a 500µm self-leveling coat, or a total thickness of 1.5–2.5 mm. These figures are not different ways of saying the same thing: each figure describes a separate coat, with a separate job, within a multi-coat system. Understanding each coat correctly helps you read quotations, read technical documentation, and talk to contractors more accurately, instead of only comparing total thickness.
This article presents the general framework of epoxy materials. The figures below are orders of magnitude commonly found in epoxy coating systems in general, not confirmed specifications of a specific Kadier system. The specific parameters of each coating system must be taken from the official technical data sheet (TDS) of that system when available. The standards TCVN 9014:2011 and TCVN 12574-2018 are mentioned as general reference bases, not as a substitute for a site survey of each individual project.
Convert units before reading figures: µm and mm are one
1 mm equals 1,000µm. A 50µm primer coat is therefore 0.05 mm, a 500µm self-leveling coat is 0.5 mm, and a total thickness of 1.5–2.5 mm is equivalent to 1,500–2,500µm. The most common confusion is comparing 500µm with 2 mm without converting units, and then concluding that the 500µm coat is “much thinner” than a 2 mm system — whereas in reality 500µm is only one coat within the system, while 2 mm is the total of several coats added together.
A simple rule for reading figures: always ask whether the figure is the thickness of one coat or of the whole system. A 50µm primer coat cannot be compared directly with a finished 2 mm system, just as the thickness of one brick cannot be compared with the height of an entire wall.
The primer coat, about 50µm: the thinnest coat, but the one that determines adhesion
The primer is the first coat in contact with the concrete substrate. Its main job is not to bear load or to create a level surface, but to penetrate the substrate surface, seal small pores, and form an adhesion bridge between the concrete and the coats above. That is why the primer is usually very thin, on the order of a few dozen µm.
A thin primer does not mean the primer is unimportant. On the contrary, most peeling failures start at this stage: if the substrate is still damp, dusty, greasy, or has not been ground open, the primer cannot adhere, and the whole system above loses its support. At acceptance inspection, the primer is usually not measured by eye, but assessed indirectly through the adhesion of the whole system.
For Kadier coating systems, the official TDS must be consulted to know what type of primer each system uses and how it is applied; this article does not state a primer specification specific to any individual system.
The intermediate coat and the self-leveling coat, about 500µm: the coats that level and bear load
After the primer comes the intermediate coat, which may be a roller-applied build coat or a self-leveling mortar coat. A self-leveling coat of about 500µm (0.5 mm) is an order of magnitude commonly found for a single self-leveling pour in industrial flooring systems in general. This coat does three jobs at once: leveling small unevenness in the substrate, building thickness to resist wear and impact, and providing a level base for the topcoat.
Unlike the primer, the self-leveling coat must be controlled with tools: a notched squeegee of a set size, a wet-film thickness gauge during application, and a dry-film thickness gauge after curing. If the self-leveling coat is poured unevenly, the floor surface will have thick and thin spots; thin spots wear faster, and thick spots may crack from uneven shrinkage.
The self-leveling LevelFlow system is a Kadier coating system in the self-leveling group; the specific thickness and consumption parameters of this system must be checked against the official TDS, and the 500µm figure in this article must not be taken as a specification of the product.
Total thickness of 1.5–2.5 mm: the total of the whole system, not of one coat
When documentation states that a coating system is 1.5–2.5 mm thick, that is the total dry thickness of the whole system after completion: primer plus intermediate coat plus topcoat, sometimes plus a leveling mortar coat if the substrate is poor. A 2 mm system may consist of a 0.05 mm primer, one or two intermediate coats of about 0.5–1 mm each, and a topcoat of about 0.2–0.5 mm. This way of adding up explains why two systems both stated as 2 mm can still differ considerably: the number of coats, the type of coat, and the role of each coat are what determine performance, not only the total figure.
A greater total thickness is not automatically more durable. A thick system with poor primer adhesion will still peel; a thin system on a good substrate, with a firmly adhering primer and a suitable topcoat, will still last well in a light-traffic area. The article Epoxy Coating Thickness 0.2–3 mm: How to Choose? explains how to choose total thickness according to load and traffic; this article only explains the build-up of each coat so that you can read the figures in documentation.
The topcoat: a thin coat that directly takes every impact
The topcoat is the final coat, usually only a few hundred µm thick. It is the coat in direct contact with wheels, spilled chemicals, cleaning water, and light. The topcoat therefore determines color, gloss, anti-slip performance, and surface chemical resistance, even though it is not the thickest coat.
A flooring system can fail at the topcoat while the coats below remain intact: a worn surface, discoloration from chemicals, or slipperiness when wet are topcoat failures. In such cases, repair often only requires treating and recoating the topcoat, not necessarily redoing the whole system — but that decision must be based on checking the adhesion and condition of the coats below, not on a visual guess.
How to check thickness at acceptance inspection
Wet thickness is checked during application with a wet-film comb placed on the freshly applied coat. Dry thickness is measured after curing with a dry-film thickness gauge on a metal substrate, or by cutting a test sample for a concrete substrate, depending on the method applied by the acceptance unit. Whichever method is used, the important point is to measure many points across the floor surface, especially at spots prone to thinness such as wall edges, column bases, and areas repaired locally.
When receiving an acceptance report, you should check three things: whether the figure stated is a coat thickness or a system total, the number of measurement points and their locations, and the permitted tolerance if one is stated in the agreement. A report that states only one total figure, without the number of measurement points, is not enough to conclude that the system meets the requirements.
Common misunderstandings about thickness
First, “thicker is better” is not true in every case: coating thicker than necessary wastes material, extends curing time, and can cause greater shrinkage stress. Second, “the primer is thin so it can be skipped” is a costly mistake, because the primer determines the adhesion of the whole system. Third, “measuring one point is enough” does not reflect application reality, because thickness always varies with workmanship and substrate flatness.
Choosing a coating system should start from function: a light foot-traffic area, a forklift area, or a chemical-exposed area need different coat build-ups. Once function is settled, consult the official TDS of the coating system to know the coat build-up and recommended thickness of that specific system. The roller-applied RollCoat system suits ordinary roller-applied areas, the self-leveling LevelFlow system suits floors needing high flatness and thickness, the water-based AquaBase system suits areas needing low VOC, and the anti-static StatGuard system suits cleanrooms and electronics plants — choosing a specific system for your project must be based on the TDS and an actual substrate survey.
Request a consultation to compare coat build-up and thickness suited to the load, traffic, and actual substrate conditions of your project before finalizing a coating system.
Illustrative image: painting tools and a roller with paint (Source: Ivan S / Pexels).
