Should wall tiles be fitted flush to the top of the shower tray before silicone or tiles fitted?

HI. When the shower tray is fitted a bead of silicone should be put between the tray and wall, and then tiled down to the tray leaving a few mm gap, and then after it is grouted another bead of silicone from the tiles to the tray. It may be also worth checking as to whether it has been siliconed up the corner of the wall as well, as movement in the wall can cause leaks, and it should also have been sealed at the bottom between the enclosure wall profile and the wall. It depends on the type of tray as to whether it should be bedded on cement or not. Generally stone trays are bedded so as not to leave any hollow areas. Hope this helps. David. Storey Plumbing.