Spin Semiconductor

In a dual layer pcb I allways use a bottom layer ground plane but think about adding a top layer ground plane. My question is, if an improvement or can lead to ground loops?

A single solid ground plane is the best. If you add an upper one it will not be solid due to the other routing on that layer and you do risk ground loops.

Rule of thumb is always one solid ground plane unless there is a real reason (safety issue, etc.) to have split ground planes. And in that case you need to consider the current return paths.

Great Frank, my assumptions were correct, the bottom plane is really solid so I'll stick to that.