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Weber Saint-Gobain - Official website of the company

Direct-applied rendering over existing masonry

Existing masonry is designed as a finish in its own right. It may not be suitable to accept a direct application of render.


1. Dirty deposits accumulated over a period of time

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Dirty deposits can form a weak intermediate layer that interferes with the development of the bond of newly applied render.

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2. Organic Growth

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.

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3. Poor key

Renders need a combination of mechanical key (texture or roughness) and suction (absorption of the most liquid elements into the substrate) to bond to the wall. Existing masonry surfaces seldom have sufficient key to hold a new render.


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Treat, then apply weberend aid and suitable render

Assessment and preparation is of paramount importance. Preparatory key coats are very heavily polymer modified to `stick' to `smooth' substrates and are finished with a deep mechanical key to hold the new render.

Solution with the following Weber products

Solution 1

weber CL150

Masonry biocide which can be used on most exterior surfaces

weberend OCR

Pre-blended single coat application renders

weberend aid

Preparatory key coat for rendering

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