Help with Outdoor Wooden Table

Hi Gang,

I am brand new to mosaics and I need advice. I have a wooden table that I'm building that I want to top with tile. This table will spend all seasons in Nor Cal outdoors. I was told by our local tile store that if I adhere tile to a wooden table that they will pop off after a few years because the plywood will warp over time and loosen them.

How can I work around this? I do not want to use cement board to top the table because that plus the mastic and tile will add too much height to the table.

Can I put a sheet of metal on the table top? Will tile be able to stick to it?? If you have any other solutions I would love to hear them!

Thanks!