Renovation of old, uncracked and load-bearing facade renders

Intact render facades can simply be covered with a mineral, if the old one is not painted.
However, careful inspection of the old render is necessary. Hairline cracks that may be present only in the top coat, do not require any additional treatment.

Refurbishment

Simple & safe to the goal

Check of substrate

1. The render surface is run off with wire or a thin metal rod.
Alternative: the surface can be tapped with a hammer. A dark sound appears in the hollow areas.
2. Check the substrate porosity via wetting test. Water should be soake 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.
Preliminary works

4. The whole facade must be cleaned with a high-pressure cleaner.
5. Repair the knocked-off areas with a lightweight lime-cement underlay 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 primer.
Application

7. Either apply a thick-layer underlay render on existing rilled render topcoats without intermediate coat or a reinforcing mortar, like weber.therm 300 manually or mechanically in a thickness of 5 - 8 mm. Rule level with a straight edge (for ex. aluminium beam).
8. Leave the surface of the base coat / reinforcing mortar as required for the specific overlay render (top coat); in case of scratch renders with a hard broom or a notched trowel.
9. Depending on 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.
10. The overlay render is applied either by machine or hand.
11. Depending on the render type, the surface is textured or scraped with a suitable tool.