adding ratings to FAA PPL

[sick_bag]

hello, does anyone know whether you can add ratings to a FAA PPL issued on the basis of a UK licence? Or do you have to get a standalone FAA ticket? i vaguely recall that you do..

Reason for asking is that i'm going to florida soon and would like to get a floatplane rating for a bit of fun..

also, i believe a rating like this would be transferable to your UK licence when you return.

thanks!