Repair of non-active cracks on facades

The repair of static (stationary or slightly moving) cracks is most safely carried out with an ETICS (see also application tip: "Repair of cracked facades or joints with an ETICS"). If only the render must be renovated, the following steps must be followed. Depending on the type and extent of the cracks, it must be expected that even the new render will not remain crack-free.

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 absorbed 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. The knocked-off areas are repaired with a lightweight lime-cement render, such as weber.dur 132.


    6. In the case of strongly porous substrates (water is soaked immediately) the silicate fixative weber.prim 406 can be used as a primer.

  7. Application

    7. In case of active cracks knock off the render in a width of 20 cm on both crack sides. Fix the glass-fiber joint mat weber.therm Glasfaser-Fugenmatte with the bonding and reinforcing mortar weber.therm 300. In case of larger movements within the substrate lay a corrugated paperboard for purpose of decoupling. Place a galvanised, welded wire mesh (for ex. Distanet) tension-free and apply weber.dur 132.


    8. Apply a bonding and reinforcing mortar, like weber.therm 300 (5 - 8 mm) by hand or machine: Afterwards insert the woven mesh weber.therm 310; it must lay in the upper third of the mortar layer.


    9. In case of thick-layer overlay renders, e.g. 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 (top coat) 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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