Concrete, mastic asphalt, different types of screed: the substrate you are working with is the key factor in your choice of coating. This means that you should first check exactly what kind of substrate you are standing on. Only then can the sealer or coating process begin.
Each floor consists of a base layer and a wear layer. These must be securely bonded together to ensure the floor remains functional for the long term. If you want a successful floor renovation, you should first identify and assess the substrate correctly.
We have compiled the most common substrates and their properties here.
Concrete | Cement screed | Magnesia screed | Calcium sulfate screed (anhydrite screed) | Mastic asphalt |
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The higher the floor load and the more complex the coating system, the more thorough the pretreatment needs to be. Dirt, oils, greases, dust and abrasion residues, non-bearing old coatings, chemicals and other contamination must be completely removed. This also applies to sanded surfaces, sintering layers and cement sludge.
In general, a substrate to be coated must be solid, dry, clean, with good adhesiveness, load-bearing, dimensionally stable and free of separating agents or other intermediate layers affecting adhesion. The substrate must also comply with the relevant technical construction standards.
Roughen small surfaces with suitable abrasives, steel brushes or mechanically rotating brushes and then clean thoroughly with an industrial vacuum cleaner.
For highly compacted, power-trowelled concrete surfaces and substrates treated with thick coating systems, milling or shot blasting is the correct preparation.
Once you have tested and prepared the substrate, it’s time to apply the sealer or coating as part of the system build-up. But what’s the difference between a sealer and a coating?
In a sealer, the layer thicknesses are between 0.1 and 0.3 mm after several coats by rolling or brushing. This reduces wear and dust formation and improves cleanability.
However, as a sealer has only a relatively low wear layer, this method is only suitable to a limited extent for the level of mechanical stress common in commercial areas.
In a coating, the layer thicknesses are between 0.3 and 5 mm. This makes them more resistant to mechanical and chemical stress in both wet and dry areas.
There are two application methods: thin coatings applied with a roller and self-leveling thick coatings applied with a trowel or spreading knife. The result: a particularly even surface with high protective properties.
The performance of a floor coating depends on the moisture content of the substrate. A CM device (calcium carbide method) is the most reliable way to determine moisture content. More than 4% moisture by mass in concrete, for example, requires special systems for additional coating. Depending on the coating system, the substrate must not exceed the following maximum moisture values:
Core sampling is recommended for substrates that are saturated with moisture on the back or heavily oil-stained and dirty, or if the floor structures are unclear. The cross-section reveals everything: structure, strength, degree of oil contamination, etc.
This allows several millimeters of a surface to be removed efficiently. Milling is recommended for old coatings and reactive resin coatings, for example. Then: finish surfaces using dust-free shot blasting.
In the “Blastrac” process, also known as dust-free shot blasting, steel shots are propelled onto the floor by a centrifugal wheel. The removed material is vacuumed up and the steel shots are fed back into the centrifugal wheel.
This method is virtually dust-free. In many cases, rooms can remain in use during surface preparation.
Testing and coating
The substrates to be coated – concrete and screed surfaces – must exhibit sufficient adhesion and be solid, dry, load-bearing and clean. Hollow spots indicate a lack of adhesion and require corresponding measures. A common test of surface strength on the building site is the scratch test using a utility knife.
