Building first layout.... Any advice?

[Andrew Falconer]

The mountain would be at one end of the room.

The double-track bridge would be at the other end of the room.

You would need a pair of double-track wide tunnel portal if the double-track mainline has to go through the tunnel

[Buckeye Riveter]

Procure one O gauge tunnel portal.  You now have the needed vertical clearance for almost 99% of all rolling stock produced.  See clearence problem below. 

Look closely at the benchwork below and you will see pre-drilled holes for wiring.  I then pre-wired the track and accessorie buss wires before installing the foam over the benchwork.   

 

[Andrew Falconer]

The benches to support the foam sheets can be 3 feet wide around the wall to leave you an open area of just over 3 feet wide.

[Andrew Falconer]

First you need a smooth sky backdrop.

You need to use 2" thick to 3" Extruded Polystrene Foam sheets, supported by a wood frame. You can use a Wallmate extruded foam sheet as a base.

The lighting in the room has to be placed in a way to illuminate the sides of the freight trains, without the viewer casting shadows. New LED lighting bulbs and strips can be used to make the lighting bright and compact.

[fifedog]

I would try 2 lines at first, each with a passing siding.  Be willing to "push" the trackwork away from the layout edge when you design.  More pleasing to train watch, and gives a place to set down your beer.

I've found that 40-46 inches is a comfortable benchwork height for going underneath to work on the layout.

Use screws, avoid nails.  I like square drive.

Color-code your wiring.

Good room lighting.

Trees.  Lots of trees.  Tell the loved-ones trees for Christmas.  Unless you're modeling Arizona, then cactus, lots of cactus.

[Firelock76]

Do what you like, there's no right or wrong here, it's not rocket science.  If you don't like the result you can always tear it down and start over.

The advice I'd give is get the trains up and running as soon as possible, everything else like decorating and scenicking can wait.  In my mind the train table is the stage and the trains are the actors.  Good actors can give a great performance on a bare stage, but the best-dressed stage is no good without the actors.  That's what I did.

[tinplatacis]

I guess a waterwing type deal is in mind, with less that 12" being available for the "bridge" between. I want a town area on 1 side, and an industrial district on the other. Preferably double track mains. I also have a loop of 042 set aside for going around and inside a mountain, to go with my version of Hogwarts and the HP loco Lionel made a few years back. 

[tinplatacis]

Space: to wrap around with 4' or less width, an area 9'-10"x16'-10".

Have 2 RW, 1 1033 for accessories and my 3356, a 1950's DC transformer, a 1053, a CW-40. Looking to run 4-6 trains. Have an unknown quantity of TO, 027 track.

[ADCX Rob]

Well, you have your work cut out for you, nearly literally. Put together your list, and specifications, of your Givens & Druthers first, and if you then have any unanswered questions, there are many here who can help fine-tune it for you. Your inquiry is just too broad to address at this point.

[tinplatacis]

I want to know what design flaws to avoid, things like that.  It will be a wrap around type made from foam core, wanna run 4-6 trains on it.