Foam roadbed?

[Point353]

Years ago (eons) in the early days of N Gauge (now Scale) there was Mosimer (check the name) foam roadbed made in Germany. My last layout had no roadbed at first, I later lifted up the track and installed this gray foam road bed under the tracks, the roadbed for the switches just fit the Mintrix powered switches I was using at the time. It did not look half bad and on the upper level of that layout it actually provided super elevation to the 18-24 radius curves I used. No I never added ballast over the foam.

The Mössmer foam roadbed was what I used under Arnold Rapido track when first starting out in N scale 40-odd years ago.
It was easy to install and had a reasonably good appearance.
I cut it into strips to match the length of each piece of track, effectively creating sectional track with integrated ballast long before such products as Unitrack, E-Z Track or True-Track were introduced.
Unfortunately, over time the foam disintegrated into a powder-like consistency. 
While it's not something I'd consider using today, it is still available:
http://www.noch.com/en/product-categories/terrain-structuring/model-railway-track-beds-and-ballast/mossmer-trackbed-ballasted-gray-99167.html

[Chris7092]

Chris, for your hot, humid environment, I'd stick with an exterior grade plywood that has an "X" as its last designating letter.  Since you'll be using it for subroadbed, it's important that you have a quality surface on which to mount your roadbed, and although CDX plywood is very common (the C & D stand for the quality of finish on either side of the plywood, D being the worst grade, and C being just a tick better) I'd opt for more expensive, but better grade BDX, or ADX if you can find it, or even AAX or BBX, with at least one side finished pretty nicely.

I'd also make all of your benchwork from exterior grade plywood, making sure to glue and screw all of your joints using a quality yellow carpenter's glue. 

After I was done with the benchwork, but hadn't installed my subroadbed yet, I'd seal everything...install the subroadbed, sand the surface you're going to mount your roadbed on and seal it too.

OR, you could construct your benchwork (with the exception of risers and subroadbed) from steel, which may be simpler, stronger. lighter and easier to work with than wood.  You certainly would NOT have expansion/contraction/warpage problems with steel.  Just use the best construction protocols for it making sure the joinery is stable.

I'd probably also paint your benchwork too before installing subroadbed...even the steel as steel rusts.

Remember to sand both the surface you mount your roadbed to on your subroadbed, and sand the top of your roadbed (if you use cork) before laying track.  This goes a long way towards giving you trouble-free rails to run on.

Cheerio!
Bob Gilmore

Bob,

Thanks for your information.  I should've specified yesterday that while the exterior climate is hot and humid, the basement generally stays the same temperature (fairly cool) and most of the humidity would come from the garage door opening and closing.  Very good idea about sealing the bench work and sub-roadbed; that didn't occur to me.  I'll post photos of my progress as I get things started.

Chris

[C855B]

... I do live in a hot and humid environment (northern Georgia), and the layout will be built in my basement which also serves as a third car garage, so temperature fluctuations and humidity will be a factor.  Any advice or experience handling this type of environment? ...

Frankly, I have a pretty good feel for your environment*, and would not use wood. As noted up-thread, I have had very good luck with XPS ("pink") foam over steel studs, without a plywood substrate. Documented in my layout engineering thread, starting roughly here.

Temperature variances are usually not an issue with model railroads - the monster is humidity, as wood fibers expand and contract with humidity. The association with temperature is somewhat of a red herring, since relative humidity often goes up with ambient temperature.

* - My wife and I were married in Ringgold 28 years ago, by y'all's locally-famous marryin' judge.

[Lphughes]

I also use 1/16" bulletin board cork for yards and sidings. Slightly less stable (slight shrinkage), but hasn't been a problem yet.

Where do you get the 1/16 cork?

[C855B]

Menards, in their office supplies department. Also available at Hobby Lobby.

[peteski]

I think that the sheets of cork gasket material sold in automotive parts stores are also 1/16" thick.

[coosvalley]

I will add Micheals to this list of places to find cork sheet and rolls.