My DAV&P is a double deck layout. Its basically made of many shelves connected to each other. I used aluminum book shelve brackets to securer the shelves to the wall. Each shelf is like a small box with a frame and a top and cross members to support it. If your curios to see if this type of construction will support the trains, keep in mind I model G SCALE. Here are some shots showing my layout. Most of my second level is no wider then 2 feet. In 2 places I had to use legs to support the upper level. This I tried my best to get around, because it makes a scenery block. In a few places I ran a chain from the upper deck to the basement ceiling. The chains where strategy placed as so they would be hidden in trees or in a building when add the scenery. I also have one spot where the upper deck would have covered up the view of my round house on the lower deck. So I simply ended the upper deck on both sides of the round house and built a 6 foot + long bridge to cover the gap. I think that worked out really well. With a little planning a double deck layout is really the way to go. I found an added bonus I had not planned on. My view of the trains on the first deck is like looking down from a birds eye view, where as looking at the second deck is more like the view id get if I where a scale person standing beside the train.
Like this? Definitely use open grid benchwork for the upper deck, takes up a lot less space height wise than L girder or such. Lower level can be anything that fits the area. Larry http://s527.photobucket.com/albums/cc354/ClinchValley/Overall views/
I haven't got as far as those guys above, but here is what I am doing (lots of construction info on the link to my blog in my signature below). I hope mine turns out as good as the pics above: Jamie
Somebody whose name escapes me and who has written a number of articles for "MR" used 2-inch thick foam on L-shaped shelf brackets. I think he used Masonite splice plates on the bottom of the foam at the section joints. Cheap, light, and fast. Maybe Bill Darnaby and his Maumee Route?
Larry (ClinchValley) is definitely right about L-girder construction requiring a thicker deck, especially if you intend having a very long run without upper deck supports taking up lower deck real estate. Most of my deckwork is L-girder, and all of it is free-standing...not attached to the walls anywhere. If I were to build this layout again, I'd want to find a different way to support the upper deck...probably open frame secured directly to the wall studs instead of L-girders on legs.
