I have built a few layouts with a plywood base and plan on building a new layout after I move to a different house. I was wondering the pros and cons of either foam or plywood base, track laying, switch machines, wiring, scenery, running noise ect.
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I always believe in using both. Plywood on bottom with 2 inches of foam on top.
On my present layout, I am using one inch foam on a Luan surface. I think it is noisier than 3/4 inch plywood, but going below grade is sooo much easier. It also makes mounting switch machines on the bottom easier.
Welcome to the forums.
With foam there is no expansion and conrtaction or swelling in hot/cold, dry/damp weather. It is ightweight, easy to handle and cut, but keep a can of anti-static spray and a shop vac handy if you cut it with any kind of a saw. Repairing a place where you took out too much is easy, glue in a new piece.
Foam can dent if you don’t protect the edges, but most folks put a facia of some sort on their layout anyhow.
If you are going to have grades on the layout plywood is good for cutting cookie cutter style. WS inclines have helped making grades on foam easier, but there is a cost.
For portable modules, I would use a piece of 1/4" luan or plywood under the lightweight foam, just to protect the bottom during moving. On a perminant layout I have seen articles where just a strap glued under the foam at each support location is used.
There are many pros and cons to both. I’m sure you will get many comments. Look them all over and see what suits your situation best.
Good luck,
Richard
[:$] So what is Luen???
Cho Cho
@cho cho: Luan is a type of plywood.
One thing not mentioned above is that you probably don’t want to kneel on foam. I use 2" or 1" foam glued on top if 3/8 plywood, even with cookie cutter. Works great, allows carving below the surface and is very strong.
same thing as luan but with an e
Luan is a higher quality ($$) 1/4 plywood often used to make interior doors. do a web search and check it out next time you’re in a store that sell lumber.
Depends on the layout you are building. If you are building a basically flat layout with some small areas below grade, flex or sectional track minimal grades if any and surface mounted switch throws or machines then foam is probably pretty good.
If you have lots of changes in elevation, want larger valleys and peaks, use under the roadbed swith contols or linkages or are handlying tracks, then plywood is the way to go.
I have built one layout for my son that was layers of 1 and 2" foam on a 1/4" plywood base and hopefully will never have to build one like that again.
On one of my modules, I used a base of 1/2 plywood, then stacked foam on top of that. If you’re going to have a flat layout, then use foam to build your layout up from that base, that’s fine. If, however, you’re going to stack foam and put you’re track on top of that, I’d advise against it. I found that wiring the track became a major pain to drill holes in the wood base to feed the wires through. I ended up drilling holes with a 2 1/2" hole saw. For my next modules, I build a frame of using 1x4, then glued the foam to top of the frame. At that time I used Liquid Nails for projects, but have since changed to using acrylic latex caulk. I have one section that’s 12" thick. I made a tool out of a wire hanger to feed the wire through the foam. It has a hole at the top and the wire is fed through the foam like a sewing needle.
I used a 1/2" plywood base over 1x framing because I had to be able to sit ontop of the layout to lay down track at the rear of the layout against the backdrop, that something to consider if its a big layout. You then work outword from the backdrop to the front laying foam and scenery and such.
I will tell you why I did mine the way i did as I a firm believer in the “there’s more than one way to build a MRR” camp.
I used 2" foam over 1" x 4" open grid bench work. The reasons for this are I always wanted to try this method after all the “Plywood Pacific’s” of the past. It is very easy to put in a stream, culvert or Hwy under pass, by just cutting into the foam. Foam is very easy to repair if a spot is damaged or not to your liking as far as landscape contour is concerned.
Your layout can be portable, movable or built in. I wanted my layout to be movable. The long part you see in the photo is 18’ x 6’. Two of us picked it up and carried it around and into the house from the garage where I had built it. Foam is very lightweight.
One thing I will never ever do again is put foam over plywood. I have a small 4’ x 4’ spot on this layout that has foam over plywood and it drives me nuts. Working through plywood is easy and working through foam is easy, but working through foam and plywood together, I found myself grrrrring a lot.
When you consider the weight we put on top of the benchwork is measured in ounces or a few pounds at best, 2" of foam without plywood is more than addiquit for the job.I have climbed on top of my benchwork by putting down a 2’ x 3’ piece of plywood to kneel on. there was little evidence I was there when I got off. I have built a lot of things in my 54 years and often use to overbuild things. I have now learned that overbuilding is a waste of money and can often be counter productive. By not using plywood you save money, and the less wood on a layout the better as far as having to worry about warping etc. I am a big fan of steel studs. Steel studs and foam are the perfect combination and steel studs are cheap and easy to work with.
As far as risers are concerned, I built mine out of spline, again just because I wanted to try it. Just Google “Spline Roadbed” in images and a million “how to” pages come up. I have 80’ or so of
Hi! And welcome to the Forums!
For me, plywood is the only way to go for a model railroad base. The foam stuff may be great for carving mountains or other scenery attributes, and may even work ok as a roadbed or scenery base. But, to support something as delicate and complicated as a layout, you really should have something solid under it.
On my24’x24’ HO layout there are six inch deep harbors and rivers and 2ft. high mountains, so I used 5/8" plywood and cut out the shape of the rivers and harbors, and buit up reinforced arc mountains (to span five tracks). I mark and cut out thee rectangular holes for mounting 96 under layout switch motors. Bob Hahn 
Even if you are building the layout prodominatly of foam, I would recommend using at least 1/4" ply as a base for the foam. Laun underlayment is relatively cheap. This isn’t so much for any strength issue but the use of the plywood will prove helpful for all sw machine mounting and any other mounting of buss wiring, etc.
There are a few different qualities of the Luan, the cheap soft core stuff @ HD and Loew’s is rather weak as compared to the better grades found at a “real” lumber yard. The junk “stuff”, you can snap a corner off w/ bare hands, won’t happen w/ the better plys on the good stuff. I work w/ all sorts/ grades of ply on a daily basis, there is a difference. If you want a better base, not that it would probably matter under all that foam, look into the Doug fir PTS/ underlay plys in 1/4, up to 1/2" Building a cabinet benchwork then go for the Baltic Birch!!! Ya right…LOL
Most of the responses have included some type of plywood as a base, or to attach turnout machines, under benchwork wiring, etc.
In all cases, the plywood only, foam only, or combination of plywood + foam has been used to more effectively suit specific needs of the layout for the model railroader. Foam, plaster, or ground goop can effectively be carved and/or built up for scenery.
CR&T must use plywood for support-strength for traction poles and its live overhead as a traction layout, and; foam will be used to build up scenery.
If you have access to How to Model Realistic Layouts: Trackside town & city scenery – Tony Koester on page 35 in "Figure 6 Modeling Metcalf – includes a construction photo where the scenery is flatter with some gently rolling hills…
…and here’s the caption: “With most of the NKP and B&O track at Metcalf in place on Tony’s layout, he is now installing the streets and structures, The main line is elevated 1/2” on Homabed to allow for ballast, ditches, and land contours." P.S.: The layout base is plywood, and the track is 1/2" above the plywood.
Ok, gotcha. Sort of like Baltic Birch plywood from Russia with 2 times the lamination than normal 1/8 inch we normally get in North America.
Chu Chu
I enjoyed your post, as I am about to put together a smalle 30" x 54" N scale layout and was going to use the plywood/foam as a subroadbed. I agree that 2" foam is strong enough and with 1"x4" framing and 1"x2" supports - this should work and be light enough for a small portable layout.
Personally, I find neither solution all that appealing. I prefer an open grid - even for a shelf layout. But then I don’t like flat layouts, nor do I model a level prototype. Depending on the situation, L-girder or box grid, using lumber or plywood strips all work fine to construct the grid. L-girder with lumber is perhaps the fastest for an incompetent carpenter like me (cuts to the nearest 1/4" or so). Thin plywood grid is the slowest to construct but is the lightest.
Subroadbed up on risers - can use spline, plywood, or foam for subroadbed. Nice thing in the early stages is the easy access for wiring, switch machine and uncoupling ramp mounting, and the like. With the subroadbed and roadbed on risers, scenery features can be any elevation I want them to be.
I have started with a flat table top layout (both foam and plywood) in the past, but ended up cutting out the subroadbed and putting it on risers later on (cookie cutter construction). Somewhat wasteful of materials that way.
Comparing plywood and foam -
- plywood requires basic carpentry tools - saws, drills, screws. Foam takes knives and glue.
- foam is much, much lighter. But this only matters if you are carrying or moving a layout section.
- foam doesn’t change with humidity changes. This is a non-problem in most homes with plywood - but the potential for problems are there with plywood.
- foam is much thicker for the same structural strength. This makes switch machines and under the track uncoupling ramps more difficult. Areas where one track is above another re
I would like to say thanks to all of you that have sent replys. Has anyone noticed a difference in track noise on foam or plywood. I have always used cork roadbed. All of my rolling stock has steel wheels. Keep sending replys and hopefully this post will help other modelers as well.