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FIXING SHEETED UP MOSAIC

It is important to read these instructions fully before you start work.
This fact-sheet describes how to fix mosaic supplied on paper. The sheets are placed paper‑face upwards into an adhesive bed and then the paper is peeled off. The mosaic is then grouted.

Materials

1. You will need the mosaic sheets, cement‑based tile adhesive, tile grout, jam jars/mixing pots, a notched tile adhesive spreader (3mm notch is best), grout spreader, tilers sponge, rubber gloves, face mask and a stiff backing boards larger than the individual mosaic sheets. You may also need tile nippers and protective goggles if you have to cut the mosaic to fit.

Fig 1: Cut mosaic tiles by placing nippers at the edge of the tile in the direction in which you want to cut.

Preparation

2. You must make sure that the surface to which the mosaic is to be fixed is flat and firm. A mosaic should not be fixed to an unsound surface eg. cracked or crumbling plaster, broken tiles etc. A bad base is one of the most common causes of failure of mosaic fixing. When fixing to a floor make sure that it is solid. There must be no movement or the fixing will fail. Floorboards should be covered with ply boarding screwed down at 9" centres.

When fixing to walls use a plumb line to mark a vertical line on the surface from which you can lay the mosaic sheets. Use the line as a starting point for fixing the mosaic and work into the corners. When fixing a floor it is best to lay out the sheets in advance to see how they will fit the space and base your fixing plan on the result.

Fig 2: To avoid obvious sheet joins, stagger the joints between sheets if possible.

Spreading adhesive, laying mosaic & peeling off

3. Mix the cement based adhesive with water to achieve a smooth, thick consistency. Allow about 1kg of dry adhesive per 0.75m2/5 sq ft. of mosaic. Wearing rubber gloves use the 3mm notched adhesive trowel to spread a thin bed of adhesive evenly on to the surface on which you intend to fix the mosaic. Try to ensure even coverage over the whole area to be "mosaiced" and when fixing more than one sheet apply the adhesive over an area slightly larger than the area of mosaic to be fixed. If the area is large you can do it section by section mixing fresh adhesive for each new area. The sheets should then be placed carefully onto the adhesive and pressed firmly into place. Be careful to make sure the gaps between the sheets are identical to the gaps between the individual tiles so that the sheet joints do not show up. It is also advisable to offset the sheets in relation to each other to make the junction between sheets less obvious (see Fig 2). If you need to make some adjustments to the spacings you can peel off the paper before the adhesive is completely dry. If you peel too soon you may pull the tiles out of alignment, so wait for 20-30 minutes, depending on room temperature. Wet the paper and leave for 5-10 minutes so that the glue is dissolved and the paper can be peeled off without lifting the tiles. The paper should be pulled parallel with the face of the tiles. You can also scrape out excess adhesive at this stage. If you are happy with the layout of the sheets and the thickness of the adhesive you can leave the paper on until the adhesive is dry and you are ready to start grouting.

Fig 3: Gently peel off the paper by pulling parallel to the face of the mosaic

Grouting & cleaning

5. The final stage is to grout the mosaic when the adhesive is completely dry. This should be done by using a grouting squeegee. The aim is to fill any gaps between the tesserae with grout and give the mosaic an even surface. Surplus grout should be wiped off before the grout dries on the face of the tiles. Cover as large an area as you can before cleaning off the excess with a squeezed-out damp sponge. Use only a clean face of the sponge for each wipe to avoid spreading the grout back over the tiles. When the grout is almost dry polish the surface with a clean dry cloth.