Interview of:

Lorenzo Vedovato

Technical Services, M+ (Italy)

From Realtà Mapei International n° 94 - 12/14/2022

Installing mosaic

Best practices for a professional result

Thin, beautiful and versatile, mosaic is widely used in contemporary design in wellness centres, gyms and swimming pools, as well as in private homes, and enable refined and decorative surfaces to be created in a wide variety of styles and colours.

The correct procedures for installing mosaic and the most suitable products depend on the type of surroundings (damp or not damp) and substrate. Let’s take a closer look in more detail.

What are the essential requirements of a substrate before installing mosaic?

It is very important that the substrate on which mosaic is to be installed is flat, compact and free of all traces of dust. Also, if there are any expansion joints, their position must be respected. In addition, screeds must be correctly cured to avoid cracks forming later due to hygrometric shrinkage. Once these basic requirements have been met, if the area where the mosaic is to be installed is damp – such as in a Turkish bath or shower, for example – the surfaces need to be waterproofed using products such as MAPELASTIC, which is applied in two layers with a trowel, with glass fibre mesh, such as MAPENET 150, embedded between the two layers to even out the thickness and absorb potential expansion.


Is it possible to install mosaic over existing ceramic tiles?

Yes, is it possible, thanks to mosaic tiles being so thin. Before installing them, however, it is important to check that the ceramic tiles are well bonded to the substrate: if they are not well bonded, it would be better to remove them completely. Once their bond to the surface has been checked, wash and degrease the tiles with a suitable product, such as 5% caustic soda granules diluted in water. If the tiles are shiny, they need to be abraded with a suitable grinding disc. Then skim the surface with a proper skim coat and install the mosaic.


Which are the most suitable installation and grouting products?

On cementitious substrates you need to use C2 TE S2 type adhesives, that is, improved cementitious adhesives with no vertical slip, extended open time and high deformability. One such example is the Adesilex P10 + Isolastic system mixed at a ratio of 1:1. For grouting joints, an epoxy product is usually used – such as KERAPOXY EASY DESIGN – which, apart from coming in a wide range of colours, is mechanically strong and resistant to acids.

On other types of substrates, such as styrene for a Turkish bath or a pool, or metal in the case of the walls of a boat or ship, we would go for a product with a high modulus of elasticity, such as ULTRABOND ECO PU 2K polyurethane adhesive. In this case, too, they should be grouted with an epoxy product.


What type of support does M+ provide for installing mosaic?

If the client that intends installing our mosaics requests assistance, we carry out a survey to assess the condition of the substrates and then recommend the best product, after which we follow the site until the completed work is handed over.

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