The layout is a multiple deck, shelf style layout. Normally the deck is less than 12" wide; it does bump out to 24" at the major yard, which is my version of Acca Yard. Like most modelers, I had to compromise in what would fit and what would work well when it comes to operations, so the classification tracks are single ended, rather than double like the prototype.
The track plans should be considered "baseline" type of documents, as the as-built railroad differs from the track plan in a couple of spots. Hopefull they give enough insight that the reader can understand the size and scope of the layout.
The benchwork is mostly built from 3/4" plywood; I ripped the sheets of it down to 3" wide strips that I then used to provide joists and other support framework. One thing I discovered is that the big box stores (Home Depot and Lowe's) sell 3/4" plywood that 1. isn't 3/4" and 2. Isn't consistent from 1/16 to 1/4 from a nominal 3/4" inch thick. Fun times occur when you try to match up your subroadbed and find issues like this.
I started benchwork with the lowest level staging yard, which is 33" or so from the floor at track level. I build the benchwork somewhat like modules or dominoes in 8 foot long sections. I made an attempt to make things somewhat modular to make it easier to remove when the time comes to sell this house. As time went along, I moved away from the truly modular style and just built things in place once I realized that trying to fit a shelf style layout into a different room than what it was built in was probably a fool's errand and that I should save the time spent in engineering modular solutions and use it elsewhere. The upper level reflects this change, as it is homasote on top of 3/4" plywood with offset joints. (Something else learned during contruction.)
When I first started laying track, I used the Woodland Scenics roadbed product, Track-bed, instead of cork, thinking that cork was "old" technology. Turned out that cork is easier to deal with and, as a big bonus, holds spikes very well, making track changes or reuse very easy. The track-bed, does not hold spikes, meaning you have to glue track down. This means that a good portion of the mainline will end up in the dumpter when I move anyway, no matter how modular I made it.