Adhesive and sealer for mosaic tiles.

15 Oct 2008
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United Kingdom
I'm putting a 2" deep strip of mosaic tiles as a feature around the middle of a bathroom. The rest of the wall area will be ceramic tiles. I don't want to buy a tub of adhesive specially for the mosaics and wondered if it would be OK to use ordinary instant grab adhesive. What's best to use as a sealant for the mosaics? Advice much appreciated.
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What substrate are you tiling onto?

Main tiles.... Ceramic or porcelain or Natural stone? What size are they?
Mosaic tiles........ Ditto? :)
The substrate is an old but solid brick wall, cement plastered and skimmed.

The main tiles are ceramic 13"x10" (metric equivalent). The mosaic tiles are from Travis Perkins, a mixture of glass and natural stone on a web backing.

I've already tiled two of the walls but not sealed or grouted yet. I fixed the ceramic tiles with normal tile cement. I left a 2" channel for the mosaics, fixed a batten to the wall and continued tiling above. The following day I removed the batten and fixed the strips of mosaic tiles in the channel using a small blob of instant grab adhesive on the back of each tile. This was a week ago and it all seems nice and solid now.

I'm still not sure what to use to seal the mosaics. On the packet it says they should be sealed after fixing but before grouting, then again after grouting.

The other two walls will need to be tanked because of the bath and shower. I'm not sure whether the tile cement and adhesive I've used already will be suitable on the other walls on top of the tanking membrane.
Personally i use powdered adhesive for everthing. Much stronger as tubbed adhesive can go mushy after a prolonged period in contact with water, so.......

All walls to be primed with an acryllic primer like BAL APD. Tank the 2 wet walls with BAL WP1 or ardex WPC. Then use a white slow setting flexible adhesive like Mapei keraflex. Not grey, cuz that can bleed into the stone and discolour it permenantly. If the stone is matt finish, use LTP Mattstone to seal it. If its polished, LTP MPG sealer. Grout it with a flexible grout (mapei ultracolour is awesome stuff as it has a built in water repellant). When dried and cleaned off, another coat of sealer.... Bosh! Bobs your uncle and Kath's your aunt.
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One more thing.... NEVER BLOB TILES. Also called dotting and dabbing..... it leaves to many voids for moisture to travel behind. In wet area you must have 100% even coverage of adhesive in wet areas, minimum 70%even coverage in dry areas. For the main tiles, use a 6x6mm square notch trowel.... also back butter the tiles. Use a 3x3 or 4x4mm for the mosaics. Pack out if need be with a solid bed of adhesive. Thickness will depend on the depth difference between the main tile and the mosaic.

I've already seen on this forum where people think its acceptable to Dot And Dab tiles and mosaics...... its not. Tiles are expensive things to get wrong so do it by the book and you won't have any problems.

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