Repair of salt-loaded and damp-damaged facades

Old facades are often damaged by moisture and salts that have migrated into the construction. Chalking surfaces, spalling plaster, moisture penetration, surface discolouration and cracking are the result.

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    1. If the waterproofing is damaged or missing altogether, moisture can penetrate the masonry unhindered. With the moisture, salts also migrate into the pore structure or are dissolved in the wall material. These include chlorides, nitrates and sulphates.


    2. A light-coloured stripe gradually forms on the surface of the facade due to the deposited salt crystals. In this area (H-h), the moisture content in the plaster mortar varies depending on the season. The moisture that has risen in the wall evaporates on the surface, leaving the salt crystals behind.


    3. Salts are also deposited in the pore structure of the masonry and plaster. They clog the pores. When the moisture in the plaster freezes in winter, the pore structure can no longer absorb the increased pressure and damage occurs to the plaster surface.


    4. For restoration of masonry and plaster, a damp-proof render with a high pore volume must be applied. Rising damp in the masonry can quickly penetrate the damp-proof render and evaporate.


    5. Due to its high air void content, a damp-proof (restoration) plaster can absorb and deposit salts. Moisture that has penetrated the plaster can thus expand without danger.


    6. As a final coat, decorative mineral plaster or paint can be applied on top of the restoration plaster. This will not impair the evaporation of moisture.


    7. First, the moisture and the salt content of the masonry are determined by laboratory analysis.


    8. All old plaster layers must be removed approx. 1 m beyond the damaged line. Then scrape out the joints to a depth of approx. 2 cm. The knocked material must be disposed of immediately. Loose and adhesion-impairing particles are removed from the exposed masonry by compressed air or sandblasting.


    9. Missing or damaged bricks are replaced or exchanged and force-fitted into the wall assembly. The joints are to be filled with the damp-proof base coat render weber.san 162 WTA.


    10. Spray/apply the normal-setting stipple coat weber.san 160 WTA net-like with a surface coverage of 50% on the prepared masonry surface of the facade either manually or preferably with a machine. The coat should be allowed to dry for 1-3 days.


    11. Apply the damp-proof basecoat render weber.san 162 WTA or the damp-proof render weber.san 161 full-surface on top of weber.san 160 WTA in a thickness of 20-30 mm. Whenever a damp-proof plaster in a thickness over 30 mm is required, apply the damp-proof basecoat render weber.san 163 WTA beforehand.


    12. After a sufficient waiting time of approx 1 day per mm thickness a mineral overlay render, like 261 AquaBalance can be applied.

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