I’m building my first layout after 40 years away from the hobby (I dabbled in it a little in high school, then have been “armchairing” ever since). I’m going to use insulation foam as a layout base, on top of 1/4-inch plywood. I’m modeling in HO.
Originally was planning to use 2-inch-thick foam on the base. But because my track plan calls for an elevated area, I think I’ll put the raised track on 1-inch foam, which would be on top of a 1/4-inch plywood support. So now I think for the base layout instead of 2-inch thick foam I’ll do 2 layers of 1-inch foam, with the top layer being raised “cookie-cutter style” for the grades up to the upper level.
So will the 1-inch thick be thick enough for the upper level, esp. if supported by 1/4 inch ply?
Also, will there be any problem in using the two layers on the lower level instead of one 2-inch layer?
(And yes, I do plan to install cork roadbed under the track and on top of the foam to deaden noise.)
I have an N-scale pike and I used 1" foam on luan plywood and I’m very happy with the results. It’s sturdy, yet I can cut down into the foam for scenery purposes. The plywood allowed me to easily secure things like switch-machines.
Welcome to the forums and back to model railroading.
I would recommend 2" for your base. It gives you more below track scenery possibilities and does not really need the plywood underneath (14.5 scale feet instead of only 7.25 feet). I do suggest at least a light frame under it though, 2’ centers will do. Also, I recommend a facia on any surfaces that are exposed to bumping, foam does get dinged edges easily. If you go with the 1" you will need the plywood underneath, as it will sag.
If you want a section of track raised track raised you can use 1" or cut some 2" down. I have multi-layered foam in places and have had no problems.
Even small pieces of foam are useful. You can make anything from small piles of dirt to large mountains (solid or hollow) with the stuff. Many folks have carved quite nice rock formations out of it also.
For foam adhesive I use cheap latex caulk. It doesn’t take much and if you use it sparingly when you put your track and cork down, with a little care most of it can be salvaged if you want to make a change in your track plan. Also, it is tacky enough to hold gentle curves, though I recommend pinning your track while it dries if you have much curve in your flex track. It dries slowly enough so you can adjust its position as you go along.
When I got back into the hobby about 5 years ago I went into HO {up from O and N as a kid and teen}.
I wanted a layout that was light weight so it could be taken down and stored if necessary or moved when the time comes that we are able to buy a “Model Railroad space that happens to have a house covering it”. It is a relatively small layout: 3.5 feet by 5.1 feet.
I used 1" foam over a grid of 1x3s one foot on center glued to the 1x3s with regular white glue. That’s it. It is plenty sturdy enough to support my HO trains and buildings. I did use the Woodland Scenics 1" foam “Risers” { flexible ramps} and WS 1" foam “pillars” {flexible 1" high strips} to vary the heights of the rails so that it was not all flat as a pancake. White glue worked for that too. As long as you aren’t going to lean on it, or climb on top, I found the one inch foam over 12 inch centers to be fine.
If I were to do it all over again, I would put down 1/4inch luan plywood over the grid work so I could mount under layout switching mechanisms and wiring etc to. I would probably use one inch foam in layers, the lowest being one inch over the luan for rivers and valleys, and the regular track being on a stack of two layers of 1 inch, and heights going up to 4 layers to give me varying heights- that is assuming I have space for a larger layout!! [8-|] I would use the silicone adhesive meant for foam to bond the layers of foam together.
Another thing to consider is layout “table top” height from the floor for working purposes. My layout is at 44" high off the floor for ease of use to work on for my height {5’6"} so I am not bending over the layout stressing my back as I work and play. Just another thought for you to consider.