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Hi. Having shower tiled - porcelain tiles on waterproof insulation board. Wall is not straight so tiler is using https://www.tilersforums.com/forums/tile-adhesive/ to level the tiles. However there are some big voids behind the edges of the tiles (see image) where there is no https://www.tilersforums.com/forums/tile-adhesive/ - these voids are at the 2-3cm edge of the tile? Will this be a problem as I understand a high % https://www.tilersforums.com/forums/tile-adhesive/ coverage is required for wet areas? Note: on waterproof insulation board. Thank you.