A lot of the time (especially on new builds or complete renovations), this can be a matter of personal preference. If you're going for a modern look, the 15mm or 18mm thickness would be ideal. If you are looking for a more traditional look and feel, 25mm thickness is the way to go (a lot of old skirting boards and architraves are at least this thick!). However, it could be that you need to choose a certain thickness in order to fit the materials properly.
This option is for choosing how thick you want the skirting boards to be (be it skirting, architrave, window boards, etc.). We offer 15mm, 18mm, 25mm and 30mm on various products.