Flooring Tile - Tile over swelled formica countertop

I would like to tile over our existing formica countertops, by cutting off the rounded edged, removing the rounded backsplash, and screwing down cement board on counter and wall. The tiles are 8x8 and we would use v-cap edges, and a new tile-in sink.

However, one diagonal seam in the formica at the corner near the sink has reacted to excess water and is slightly raised - maybe total of 1/8 - 1/4". Is there a way to deal with this, or does this make the countertops un-tile-over-able?

Thanks, SHeinz

sheinz, Welcome to the DIY Forums.
I moved your post here because Kitchens Forum is more for information about design than doing the tile work. I am sure one of the experts here will answer your questions. Good luck.

You need to take out those counter tops and start from scratch. The particle board in formica countertops is not a suitable substraight for tile. When it gets wet it swells. Tile can't take that kind of movement and will fail.

Tiling over particalboard is an absolute no-no for the reason your countertop has demonstrated. True enough the laminate would offer some protection but as you can see it doesn't take much for water or moisture to get through somewhere and wreck the surface.

To remove the existing tops and replace the foundation (particalboard) with exterior grade plywood then cement board would be the recommended method. Two layers of 3/4" ply are recommended, then the addition of 1/4" cementboard set in a bed of thinset.

The truth is....the tile and grout ARE NOT waterproof tho many seem to think they are. In addition the particalboard can expand under the influence of atmospheric moisture in some cases.:)