Laying Mosaics

Getting the picture about how to lay a mosaic

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Laying mosaics is not as difficult as I feared. As is often the case, preparation is the key and it is essential that the place where they are being laid is level, clean and keyed in ready. Ideally a mosaic should be placed on a bed of fresh concrete or render. This is the sequence we followed when fixing our mosaics.

Having decided on the location for each mosaic, rotate them until they are correctly orientated - try to get them to line up with columns or windows or centralised as appropriate. Mark the finished position on the concrete with a wax crayon or charcoal pencil.

Peel off the polythene backing from the mosaic being careful to set aside any loose chips of marble. These pieces can be fixed later; just keep them to hand for the moment.

Mix up a sufficient quantity of adhesive in a bucket - enough to do no more than a single mosaic. If you prepare more than that the adhesive will set. You may find that hiring or buying a paddle mixer (a simple attachment that fits in any drill) is a good investment.

Using a shark-toothed spreader, apply the adhesive generously to the concrete surface (do not apply it directly to the mosaic). Cover the entire area where the mosaic will go.

Lift the mosaic (this may take two or more people depending upon its size) and place it over the adhesive orientating it to match the marks you made earlier.

Using a block of wood, mallet or similar heavy blunt object, carefully tamp down the mosaic starting at its centre and working outwards. Make sure that the finished surface is as level as you can get it - use a spirit level to check this. Wipe off any surplus adhesive.

If the mosaic is to be mounted on a wall, you will need to fix timber supports underneath and on one or both sides of the mosaic. If it is a large circular one (eg a medallion) then you may even need to fix a central timber across the face to hold it while the adhesive sets (usually under 24 hours).

If there any broken pieces, now is a good time to fix them. Use any proprietary solvent-based household glue and cut the marble with pliers or, better still, with a disk or tile cutter.

When the adhesive is dry, apply a good quality tile grout, cleaning the mosaic if it has become dirty or gritty in any way. Grouts come in different colours - choose a light coloured grout unless the mosaic is to be surrounded by tiles with a dark grout. Only choose a dark grout if you are absolutely sure that this is what you want as it will make the mosaic look very stark and its image even more disjointed.

Grout is a powdery wash that is applied over the whole surface of the mosaic. As a result, it has to be cleaned off within a few minutes of it being laid. Use a clean cloth and a damp sponge for this. Make sure that you don't let the grout dry on the face of the marble pieces as this will prove increasingly difficult to remove without resorting to acid - something to be avoided if possible as it will mar the image since it dissolves the marble.

Finally use a proprietary polish (this can be purchased from hobby stores, the mosaic supplier or shops selling tiles) to clean off any remaining residue of grout.

Have fun laying mosaics!