Ground Loops in PCB design

[warpie]

With a 2 layer PCB you soon get technical limit with -top of each other- because you have no path to route anything else through this highway wall.

Ok fair enough but theoretically speaking?

 

[zamproject]

I let this answer to the expert

 

[PureBasic]

Well theoretically speaking you can already make great boards with only 2 layers. A 4 layer board will be easier to route and more robust overall. It all depends on your component density and the board complexity. I wouldn't feel the necessity to go to 4 layers for a board if your project uses trough hole components only; you should always have enough room to route everything on 2 layers in this case.
Just be mindful that the return path is as important as the signal traces you route. Work with clearances kind of close to your manufacturer limit (to limit loops area). Use a top and bottom copper pour for ground and, vias are free, so sprinkle some all over to stitch those ground planes together.