Sealing of hollow spaces under ceramic coverings

When laying ceramic tiles, larger formats are increasingly being chosen. This applies to both new buildings and renovation projects. The danger of hollow spaces under the tiles is growing. Damage and breakage can be the result, particularly in the case of high mechanical loads. In addition, the covering also sounds hollow when walking on it. For the builder owner, this is often a reason for complaint. Frequent consequence: dismantling and new installation (laying of ceramic coverings). This often presents the craftsman with problems, also in financial terms. The special liquid weber.sys 891 has extraordinary penetration properties, fills hollow spaces and can often be the solution to cost-intensive and time-consuming deconstruction. This product allows you to easily eliminate hollow spots under ceramics.

Simple & safe to the goal

  1. Check of substrate

    The substrate should be lightly tapped or wiped with an appropriate object in order to detect hollow spots. An optimal result can only be achieved if the substrate is dry.


    Local spots must be opened at the cross-sections of joints where the tiles sound hollow. For opening, either drill or cut the joints. Carefully vacuum the dust.

  3. Application

    The special liquid is now poured into the opened ceramic covering, by using suitable auxiliary tools, such as a funnel, squeeze bottle, storage container or pipette, etc. Depending on the size of the cavities, several steps may be necessary. The special liquid is poured in intervals (approx. 20 - 30 minutes) until the hollow sound is eliminated.

  4. Aftercare

    After setting weber.sys 891 forms a rubbery mass. Multiple operations are possible; the maximum time between 2 pouring operations is 24 hours. In case of wider crack or heavily trafficked surfaces we recommend the EP crack-filler and primer weber.prim 806.

  5. Grouting

    After drying, another tapping test can be carried out. In case of a good result, the areas can be closed long-lasting again with an appropriate material, like the flexible grout weber.fug 877. Beforehand, check the right colour. weber.sys 891 hardens via the addition of water. Grouting is allowed after 24 hours at the earliest.

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