hi im currently having my bathroom referbished .i am having plastic panells on the wall .the bathroom fitter hasnt used corner trim in the shower but sealed it with silicon instead ,when asked about available product trims he says that silicone is better im a little conserned as ive had silicone previously and it wasnt long before it was covered in mildew .i am paying over £10000 for referb .installer says i have to replace silicone every 3 years ,while product details on plastic boarding lasts 10years ,if used as suggested .is this just a cheaper way of doing it .
I fit this cladding and to be honest, don't usually use the trims. I believe they are only used to speed up the installation, hiding the damaged edges caused by poor cutting of the panels. If your fitter is taking the time to cut panels accurately enough not to need trims, he ought to be doing a good job.
Another thing, trims don't always seal properly and water can seep past into the joint. A silicone joint always looks heater too.
I use a brand of silicone called Forever White which has a 10 year guarantee against mildew build up so that is not an issue.