Ihave another question so please don’t get upset. If I am to use foam on the benchwork do I put down a piece of plywood then the 2" foam on top of that or do you just use the faom as the base? I am getting into N scale.
You can use just foam with a wood frame and some cross beams to support it. Just watch how much weight your going to put on it.
A cross piece every two feet is about right.
Nobody should be upset by a question, Delta1. Lothar and Soumodeler are right, though there are other issues you might want to consider. While you can certainly do it the way they have suggested, with supports every so far, and in fact that’s how I did my HO layout, it does make mounting things under the layout somewhat problematic. For instance, switch machines. You can’t really mount anything solidly to the foam. I have had to mount the switch machines on a piece of wood, and then glue that to the foam. It works, but if I now had my “druthers”', I’d opt for 1" foam on 3/8" plywood, just to make under-table mounting easier.
And make sure your cross beams aren’t going to be in the way of any under table switch machines.