Renovation of cracked, non-painted mineral facade renders

This method can be used to renovate unpainted, mineral renders on facades if these only show render-related shrinkage and stress cracks. It must be ruled out that these are construction-related cracks where larger crack flank movements occur (set plaster stoppers).

Simple & safe to the goal

  1. Check of substrate

    1. The render surface is run off with wire or a thin metal rod. Alternatively, it can be tapped with a hammer. A dark sound appears in the area of hollow spots.


    2. Check the substrate porosity via wetting test. Water should be soaked slowly and evenly.


    3. Check the strength by scoring or screwing with a screwdriver. If it does not penetrate or penetrates only a little, the old render is load-bearing enough.

  4. Preliminary works

    4. The whole facade must be cleaned with a high-pressure cleaner.


    5. Repair the knocked-off areas with a lightweight render, such as weber.dur 132.


    6. In case of too high porosity (water is soaked immediately) the silicate fixative weber.prim 406 can be used as a primer.

  7. Application

    7. Apply a bonding and reinforcing mortar, like weber.therm 300 manually or mechanically in a thickness of 5 - 7 mm. Rule level with a straight edge (for ex. aluminium beam).


    8. The woven mesh weber.therm 310 is inserted in wrinkle-free strips. It must lay in the upper third of the mortar layer.


    9. In case of thick-layer overlay renders (top coats), such as the mineral coarse-graded scratch top render 204 AquaBalance comb the reinforcement layer horizontally; otherwise roughen it.


    10. Depending on the type of overlay render and weather conditions the reinforcement layer must be eventually pre-wetted or pre-treated with the universal primer weber.prim 403.


    11. The overlay render is applied by hand or machine. Depending on the type of overlay render, the surface is textured or scratched with an appropriate tool.

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