My benchtops are 1/2 inch plywood overlaid with 2 inches (and more in some areas) of extruded foam. Cork roadbed is laid on top of this. Should I be overly concerened with expansion/contraction of the track in a room that is well insulated and heated/cooled? I live in Georgia so high humidity in the summer is the norm rather than the exception.
Thanks,
Jarrell
since you seem to be attempting to keep the tempurature within a reasonable range your only concern will be the humidity . a dehumidifier for the summer months might be a good investment . unfortunately the ones i’ve used give off heat , which will require more cooling
I don’t think you need to worry about expansion or contraction because styrofoam does not expand or contract like wood or metal do. The only place you may encounter problems would be at a joint between styrofoam sheets.
When you say cooling, you are not talking about an evaporative cooler (swamp cooler), considering where you live…right? You mean a compressor and condensor system in a closed circuit. So, you are “conditioning” the air not only by cooling it but by drying it somewhat. Therefore, you should have no problems with expansion or shrinkage during the months when your air conditioner is functioning.
It may be a different story in your “winter” way down there in the steamy tropics [:D] because the warmer you keep your air, the more humidity it will “carry.” So, you may find that you will benefit from a modest dehumidifier in the winter which will not only control that aspect, but also provide some heat…a little.
I have found nothing more than a badly deflected section of flextrack that crosses my largest bridge when I allowed humidity to climb near 70%. That was when I scrambled out to HD to purchase the dehumidifier. Within hours, the track had straightened back to where the locos and I felt a lot better about it, and the unit still runs for several hours each day.
This may be counter-intuitive, winter vs summer, but that’s the way she goes up here.
-Crandell
Yes, I use a heat pump that heats in winter and cools in summer. I don’t ‘think’ I’ll have a problem but ya never know… 
Jarrell
The one advantage of a dehumidifier over the a/c is that the former has a humidistat, and therefore responds directly to the changes about which you worry the most in this context. So, your heat pump should offer some benefit, but time will tell if you need the real McCoy.
-Crandell
The rail movement is minimal to the expansion/ contraction of the wood. Too many times the rails are blamed when it is the benchwork. Since you have laminated the benchwork w/ foam and glued the track any movement would be very slight and probably unnoticable except for extreme and prolonged humidity.
Your AC should control the envirorment, and let you run happily ever after.
Bob K.
Much obliged for the help.
Jarrell
I have a bridge that’s 54" long - two lengths of Peco flextrack cross it but aren’t tacked down. It passes over an electric fireplace. My wife had the fireplace on high one day, and I found the middle of the track had risen half an inch or more. When it cooled off, it settled back into place.