Check of substrates

The completed tiled covering is only as good as the substrate allows. Therefore, check the substrate carefully and prepare it for tile fixing. The substrate must be dimensionally accurate and technically suitable in order to allow a flawless ceramic covering on it. Dimensionally accurate means sufficiently level, flush, horizontal or with the planned slope. Technically suitable means load-bearing, clean, dry, dimensionally stable and free of adhesion-impairing particles. The tests described here are intended to assess the installation substrate in order to select a suitable substrate pre-treatment.

Simple & safe to the goal

The visual inspection

Every substrate inspection should start with a visual inspection of the entire surface. Rough defects can already be detected and an initial assessment of the substrate is made. The further test methods are then determined on this basis.
The dimensional accuracy

The dimensional accuracy of the substrate is checked using aids, such as a folding rule, spirit level, straightedge, string, plumb bob or laser levelling device.
Documentation

All activities must be documented in relation to the construction site and added to the construction file.
The grid scoring test

1. Using a pointed steel nail or a hardness scoring device, score several lines parallel to each other at a distance of approx. 6 mm.
2. Then repeat this procedure at an angle of 40°-60° to the previously scribed lines so that a diamond pattern is created.
3. If the surface hardness is sufficient, the intersection points of the diamond pattern must be neat and without any break-outs.
The tapping test

To detect hollow spots, the substrate should be scraped and tapped with a blunt hammer. In the area of hollow spots, a dark sound is evident. Hollow spots should be repaired by suitable measures.
The hammer blow test

1. The hammer blow test can be used to detect whether cupping and stratification are present in the laying substrate (e.g. screed). A blunt hammer is used to strike the surface at an angle of approx. 45°.
2. If a shell bursts out of the surface, the surface must be freed from the deposits by suitable measures (grinding, milling).
The wipe test

Wipe the surface with a dry cloth or by hand. If any residues of dust or other loose particles still remain, remove them.
The wetting test

1. The substrate is sprinkled with water. If the water is absorbed very quickly, the substrate is too absorbent. The absorption behaviour can be reduced by using a suitable primer.
2. If the water remains on the substrate, the substrate is weakly absorbent. If the absorption behaviour is optimal, the water is absorbed slowly but continuously.
The moisture measurement

The readiness of the substrate for covering depends on its residual moisture. Its check must be carried out by a CM device (carbide hygrometer) as a rule. The instructions for use of the respective device manufacturer must be observed.