My bathroom shower areas are tanked, but despite using the correct materials and tools, and siliconing alll the joints, water is getting through somewhere. I know this because the water find it's way out where the edge of the wall tiles meet the exposed corner of the bath on the outside. So the tanking system is working, but I'm still diagnosing where the pesky water is getting behind the tiles.
For me it will mean a whole re-grout and re-silicone. I suspect it's seeping through the grout but it all looks sturdy and solid to me, so trial and error. There's no embedded pipework that could be leaking and it only happens when we use the shower over the bath.