Direct-applied rendering over existing render
The Codes of Practice do allow for further render coats to be applied over existing render materials, however, there are hidden dangers in the process.
3. Paint, dirty deposits or organic growth
1. Existing renders are often finished with a thin coating or paint which will form a weak interface which is not suitable for rendering over.
2. Dirty deposits accumulated over a period of time can forma weak intermediate layer that interferes with the development of the bond of newly applied render.
3. Organic growth, even though it may be brushed from the surface, remains in the pores of the substrate and can continue to grow, delaminating the new render from the substrate.
Solution with the following Weber products
Preparatory key coat for rendering
Masonry biocide which can be used on most interior and exterior surfaces
Pre-blended single coat application renders
One coat, through coloured monocouche render