We built a vanity for one of our bathrooms. It has a black slate top on it. We used 5/8" marine grade plywood for the top, then put hardie backer board on top of that.
The marine grade plywood resists moisture dameage and the hardie backer board not only resists water but is the best thing you can use to stick your tiles to. It provides a nice strong, flat surface for your tiles.
When we put the plywood in it was inset into the fame of the cabinet then the backer board placed on top of it. It turned out really well.
Particle board would be a real no no. It's VERY susceptable to moisture and may even sag under the weight.
Have you considered recycling the ornate trim to be the frame around your tiles? If you removed it carefully it might look really nice!
Kate PS: I'd be glad to post a photo of ours in the binary group if you'd like to see it.
I have purchased an antique dining server which I would like to use as a bathroom vanity. And I would actually like to tile the top. The existing top is not appropriate for tiling because in has an elaborate edge and because it would be too thick. So I would like to replace it and also build a little frame around the new top to house the tiles. What's an appropriate material to support that construction? Can I go with compressed particle board (it will be concealed) or should I go for solid wood. Please keep in mind that I don't have a planer or a router. All I have is a table saw, a miter saw and a router.
Many thanks in advance!
Aaron