I don’t know if I can provide any scientific reason for building with or without plywood but here is my experience.
I built a shelf section 2’ by 10’. I did not use ply wood. Operating trains on that section always seemed to produce much more sound than my later additions were I used plywood first and then placed the foam on top.
The second reason that I placed plywood down first was for easier instalation of switch machines. I now use the plywood first and then the foam. I only use 1/4" plywood ( 6mm ) but it is doing what I want it to do
My current 4x8 layout is 1" foam board on a 1x4 frame benchwork. No plywood. Though it is really easy to install scenic lighting and is very light weight, I find the foam does seem to be noisy and just seems to lack stability. Maybe it is just me.
My replacement layout, due to begin soon will be 2" foam board on 1/4" plywood with sturdier benchwork. It will be lots heavier, but I feel it will be more “stable”.
Thanks, this is verry helpfull information for me.
The whole thing about using foam was, i thought it whould be more sound deading, seams i am wrong tho.
Maybe i should reconsider the use of foam under the tracks.
Thanks for your info
Krgds
Cor
As for foam under the tracks, I assume you mean the Woodland Scenics foam roadbed?
If so, that is what I used on the current layout. Works well and takes ballast nicely, but I did find that my heavy steam locos pound the curves (like the real thing) and loosen the track and ballast. Looking back, I would rather have used cork. I have no experience with the self-stick Ami Instant Roadbed.
My new layout will be using Kato Unitrack with the roadbed built in. With a little “weathering” it looks just as good or better than any ballast work I can do. It’s really expensive, but for my heavy steam locos, seems to work much better.
I use foam, glued directly to the top of grid benchwork. No plywood. I don’t find it to be noisy at all, but I am also using WS foam roadbed, and fastenign the roadbed and track with latex caulk, which probably helps. No issues with switch motors - I drop them in from the top (I use tortoises), first mounting them on a small square of perf board and useing the dremel to make a recess so the top of the perf board is flush with the surrounding foam. I can even get away with the stock piece of wire as it only has to stick through the perf board and roadbed.
For my current shelf railroad, I used 1 X 4 framing with 1/8 lauan board glued and screwed as the top surface. Add 2" foamboard glued to the lauan and your set. The entire roadbed surface is extremely lightweight, but sturdy.
I’m using 2x2" framing under 3/8" mdf in 4x8’ sheets and glue 2" extruded insulation on top (or more depending on the terrain). The sheets of mdf are about the same price as the insulation (foam) but the whole thing feels a lot sturdier than if I’d simply gone with the foam on the framework. I like how solid everything feels. I have yet to see how noise is as I haven’t started laying track yet, I’m planning to glue cork down as the roadbed.
Cor, thanks for raising this question, I am also about to build my 1st layout, and have heard many various methods for sub-base. I am going to use plywood on top of the bench, then I am going glue down 2" foam insulation board. I feel that this will not only reduce any unwanted noise, but also will give me stronger support for layout. I may lean on the layout ( or fall accidentally ) trying to improve/repair scenery, and I would hate to bust through 2" of foam ONLY on top of the “L” framing…not very nice!!! Sure, it will cost a little more, but when you consider the lifelong investment, isn’t it worth it?
I also intend to screw all my wood framing and plywood top. The new aircraft grade decking screws are terriific, and makes modifications, moves, much easier than trying to bang nails out. And screws do not back out over time from vibration etc.as nails will. Also, adding on sections with screws is non destructive as opposed to banking away with a hammer.
If this is a permanent layout, then go with the thin (1/8" - 1/4") plywood topped with foam. The plywood simply makes all the bottomside work easier. Terminal blocks and wire staples and switch machines can be put wherever you need them easily, rather than trying to mount directly to the foam or being restricted to the grid.
Don’t use foam any thicker than you need for your deepest depression. If the creek your’e going to cross only drops an inch below grade, then use 1" foam. On the other hand, if you’re going to have a LOT of vertical elements in the layout, and the overall size is fairly small, it may be simpler to just get a single sheet of thicker foam, which will simplify building up the hills, ridges, cliffs, etc. Either way, have fun, don’t forget the pics.