Dr. Frankendiesel aka Scott Running BearSpace Mouse for president!15 year veteran fire fighterCollector of Apple //e'sRunning Bear EnterprisesHistory Channel Club life member.beatus homo qui invenit sapientiam
Wood expands and contracts with changes in humidity and temperature much more than metal or foam, and is usually the cause of track buckling. My main concern with foam alone, other than the possibility of sagging over time if it is not adequately supported, is the way it resonates the sound of trains running on the track. I would paint or seal the 1x4 crossmembers to prevent warpage, but other than that you should have no problems with humidity or temperature changes.
We have a 20 x 40 foot HO scale layout in a building with no central heating or air conditioning here in the high Arizona desert where wintertime temperatures drop below freezing and summertime temperatures sometimes top 100. This layout has a 2x4 framework and is built on hollow-core doors topped with one inch of sound board glued in place with latex caulking. Humidity ranges from 10 percent to 70 or 80 percent, and we have had no problems from these extremes.
JBSteamer wrote:Here's the question . . . If I use two inch foam as a base, covering the front part and a strip along the back to lay that track on, can I avoid the problem of hummidity and temperature changes?
You may eliminate most of it, but I wouldn't count on it altogether.
What I would do is lay the track as you normally would. About every six feet, I would make sure that you have a gap of about 1/16 inch between two track sections. Because I favor soldering rail joiners, I would solder all the rail joiners that occur between each of the 1/16th inch gaps. Don't solder the joiners at the 1/16 gaps so they can allow for some temperature changes. Chances are that you won't get your layout completed before next winter, so if something does happen, you should be able to correct it without messing up the scenery.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.