This is my first Instructables so I will do my best to include the steps that count towards building your own.
Step 1: The Plan
The room is basically 12' X 14' and my obstacles were a door on one side a window opposite the door with two bookcases on the side and a closet.
I purchased a sheet of 1/2" plywood, I got the better quality plywood so I didn't not have to sand too much. Consulting the NMRA www.nmra.org page I found the minimum clearances and went to my next door neighbor to start cutting on his table saw.
The main loop is 2.5" wide and the part where the main loop and siding are 4.5" wide. Three curves are made to fit 18" radius nickel curves and the third curve with the siding has 22" radius and 18" radius curves. I feel 18" is the minimum radius for a layout because long cars like my Walthers Husky Stack calls for a minimum 24" radius. I have also noted that Locos with 6 wheels or more per truck bind a bit in 18" radius curves slowing the train as it goes around.
I viewed several sites and videos of ledge or shelf mounted railroads and decided that for the level of craftsmanship and tools I had, I had to attach the roadbed to the wall with strips of the same 1/2" plywood cut at 2.5" wide. I was really wanting to use crown molding to dress up the bottom of the shelf and also to help hide any wires but cost, time and my lack of skills made me think twice.
Step 2: The Buildout
I dug up all the 36" flex track I had stored in the closet and started to clean it. Even though it is nickel, it was not clean. It was going to be hard to keep the rails clean and I thought that the current would not reach the far end of the track. I used the track as a guide and cut two channels on the roadbed with a router using a 1/8" bit. Then feed wire though the channels. The wire was glued in the channels with CA gel and every once in a while I would solder a rail joiner to each wire to go around the layout.
The next step was to paint all the plywood and the right triangles used as support. The right triangles are cut from 2" x 2" squares. I decided to not attract attention to the structure and painted all the wood with the same latex white paint I used on the wall.
The roadbed was cut following my design, the sides was screwed to the roadbed with #6 1.25" screws.
I laid the track on foam roadbed, the foam roadbed was glued to the wood base with 3M spray mount, check compatibility first. Then I used tacks to hold the track in place and make sure it was straight.
To add to the layout I decided to add a 18" through Truss Bridge over the entrance door.
Step 3: Installation
Hanging the shelves on the wall was not straight forward as the walls were not straight and the measurements for all walls were not the same at all places. The shelf was screwed into the studs were available.
The wires were routed through the 1/8" channels on the roadbed and pushed through the wall to the closet where the transformer sits. I used some old 3 wire telephone wire to hook up the switches for the siding and hooked it up to a sliding momentary switch so that both switches change with one touch.
Step 4: Next Steps
Even though the layout is limited to a main line and a siding I can only run one locomotive at a time. I have looked at DCC and it is a viable next step to upgrade the layout. I have enough space to have 2 or three locos on the layout alternating them around the room.
Taking ideas and experiences from others and incorporating to yours make this a great hobby. Yes... there are a few things I would do different and most likely when I have a chance I will change them. Meanwhile I will enjoy looking at my trains go round and round instead of in a box in the closet. Perfect, no it is not perfect but prefection calls for training and experience with lots of expensive tools.... tools I would love to have but then again I need a large shop to put them in... <;o)