Foam, plywood or both?


I've got the lower level benchwork in process, but have not really given much thought to the deck material, I figured I'd wait until the time came to make that decision. Guess what? It's time. I have seen and run on layouts where the deck was just plywood, and one where there is a layer of plywood and a layer of foam. What about just foam? I see where people use 2-3" foam board, but all I can get in my area is 1". Is 1" to thin to use on its own? I live in a high humidty area, and I figure the foam board will be less likely to expand and contract, true?

Sorry for all the newb questions, but we all gotta start sometime. :D


The foanm will definately not be effected by the elements, but you are still going to have wood as the framework and sub-base it sounds like, you may get some effect. I think if you can keep the room consitant on temp and humidity, you will be okay, not sure what the % is on it being a factor.

If you are doing HO, I would re-enforce the sub-base under the foam. I didn't use plywood under mine, but now thinking it may have been wise, now that I want to put undertable switchmachines etc.
I have never seen the advantage of foam for a permanent layout. A plywood top can be cut through to go below bench level.



The cost of 2" foam is $27 bucks and a sheet of 9/16 OSB is $12. I tried all foam back in the late-70's and was never impressed by it.

Just a thought
Hi Glen. well 1 inch foam is quite thin to be self supporting. Then again if it was a narrow module you might get away with it. You can do the whole area underneath plywood thingy or just support it with joists underneath (1x2/ 1x4) stock lumber, gridwork. I think if it was me I'd be trying that. (not necessarily right, but thats what I'd do :D )

Glenn, I am in a very high humidity area and do not have any problems with the 1/2" plywood sub-roadbed. The most important thing you can do for it is to support it with 16" centers or less for your benchwork joists and risers and don't spare the screws when putting the plywood down. This will prevent warping that everyone claims will happen. Gads! People have been using plywood in model railroading for ages.

I can see where foam would be an advantage with weight, if one was going to move their layout around like a club would or be involved with modules, but that is about all. Some claim that the noise reduction is better, but much of the noise will still be transmitted through the hard shell scenery anyway.

I'd definitely use plywood under the foam because of the durability it will provide, also it gives you a place to attach support hooks [etc.] for the many wires you'll have crisscrossing beneath your layout. And as Rex was saying, if you use plenty of wood screws to secure the plywood to the frame, humidity distortion won't be a problem.
Thanks for the replies. My benchwork is 1X4 spaced 16" and where it meets the walls, 2 screws in every stud. It isn't moving without pulling the walls down. I was leaning towards foam, but that kinda hampers installation of under table switch machines. It is cheaper though. I will just go with 1/2" (or whatever the closest /16 or /32 measurement is, what's with the weird measurements anyway?). If I get sound, I won't hear much of the track noise (at least that's what I tell my wife to justify sound).

Thanks again!

Well I had better jump to the support of foam :D

Foam has more then light weight as an alternative to wood, and the other more messy methods of scenery making. As I stated I didn't use a sub-base but then again I am doing N scale and felt the weight was well within reason. As for doing scenery with plywood, you are correct, BUT you can also do the same with foam. I don't remember paying much for 1 1/2" foam in 8X4 sheets. It was actually cheaper then plywood. To find a decent sheet that wasn't bowed, easy to transport, I took the foam route. Doing scenery was a breeze, I used a serated knife to cut ditches, stacked like you would layers of a cake to make hills, then a Stanley surfoam file to clean up or add contours to the hills. (if you are thrifty, you can find scrap foam sheets at construction sites)

As for sound deadening, I can't say, I used WS foam roadbed, and my engines seem pretty quite. You can paint foam, glue to it, even plaster if you want, but I used the WS foam putty. I think while wood has definate requirements for a frame for the bench work, foam can have as strong a place in sub-base benchwork if you have supports as needed. For making a shelf layout, using wall brackets makes foam even more attractive.

If I was redoing my layout again, I would still use foam as the scenery base, but maybe a 3/8" plywood base for mounting items under the benchwork.

Dave DFUW - (Defender of foam users worldwide ;) )
Well I had better jump to the support of foam

:p :p
Just kidding!:D
No doubt that there are benefits from plywood or foam and this is probably argued as much as anything else in our hobby. I am comfortable with the use of plywood and would advise anyone to use what they are comfortable with.

One big reason I chose plywood is strength: not just for the top, but also for the overall benchwork. My layout is large and it is wide in several places causing me to have to lean and reach. If these areas were foam, it would be on the floor in pieces. I do use foam for fillers in some scenery situations, but I just can't handle chasing the mess around the room after trying to carve it. It is so much easier to chase piles of sawdust and shavings:rolleyes:.

IF...I used foam, I certainly would use a plywood support base for it.

Noise? Well, who cares? Darn, these are trains and trains are noisy. Jezz, my Challenger is so heavy it sounds like a real one rumbling through:D
RexHea said:
Noise? Well, who cares? Darn, these are trains and trains are noisy. Jezz, my Challenger is so heavy it sounds like a real one rumbling through:D
You got that right Rex! Those Tsunamies can get rather loud...!;)
I use both. Using foam on top of plywood allows you to use a much thinner (=lighter, = cheaper, =easier to work, etc) plywood. In most places I used only 1/4" plywood but increased the crossbeams (1x2 on edge) and it's STILL a lot cheaper and incredibly strong (i used to sit on it often).

All I have is the 1" stuff as well, but in many areas I have it glued into 2-3-4-5 layers thick. For the most part the plywood is flat, surfaces changes are made with foam. That makes things a lot easier!