I'm considering small room-sized layouts for use overseas in a townhouse. In my search back thru numerous publications I've collected over the years, and with the very numerous plans available on the internet, I singled this one particular two-layer, room-size layout design from a 26 year old publication 'Building Your Next Model Railroad'.
It starts out presenting the building of an action packed switching scene on a 2 x 8 shelf layout (or might be two, 2 x 4 modules). It then proceeds to incorporate that 2 x 8 scene into a compact small room-size layout that makes maximum use of the full room size (aisle in the middle). Furthermore it is double-layered for running even longer trains (10 foot long trains can pass one another!).
Some hi-lites about this two-layer, room-size layout.
1) It is designed to fit into room sizes,
a) the larger 10' 9” by 11' 9”
b) the smaller 8' 9” by 9' 9” (2' smaller on each side)
2) It is designed to squeeze as much mainline operation as possible in as small a space as possible. Trains as long as 10.5 feet can pass one another. You can route an endless number of complete trains through the 'visible' portion of the layout from either 'east' or 'west', and what you'll see is precisely what you would see in the real world; a parade of trains running just as though they really did come from somewhere (outside your modeled world) and going to some distant destination (also outside your modeled world). All that hidden trackage makes such operations possible by simply throwing a few remote turnouts (and block switches, if only DC controlled).
3) The nominal minimum radius curve is 24 inches. That's exactly the radius of only the outside curve between Kirk and Kalmath falls. The inner curves are 21.5 inches radius on the hidden reverse loop, and in the upper right and lower left corners of the visible upper level. You could make those inner curves 22 inches, but long passenger cars and articulated steam locos could hit one another with only 2 inch spacing on the curves.
4) There are fairly stiff 2.5 percent grades on this layout, another compromise needed to squeeze mainline operations into such a small space.
5) One of the confusing aspects of the plan when squeezing so much operation into such a small space is the need for some tracks (particularly in the 3 corners opposite the doorway) to be placed directly above one another. If you use open grid style bench work, 1 x 2 supports shaped like football goal post can support the upper level plywood sub-roadbed. (build lower level track first, test and prove it, then add upper level). You can access those lower level tracks from both beneath the layout, and from the 3 hidden access holes that will not be blocked by any scenery at this lower level.
The plan shows the sky backdrop curving in front of all 3 of those access areas at the upper level. Its suggested that one curve of the sky backdrop around the corners of the room, and extend the hills above eye level so just the tops of the hills hide the forward edges of the access holes. That is obviously a lot easier to accomplish if you are modeling the Rockies rather than recreating Kansas.
