01-16-2011, 09:55 AM
When you think about it any heat conductor will expand and contract with heat and cold. Insulators will not. On the other hand, any porous substance will soak up water or dry out and expand and contract with humidity. Generally our bench work is wood, a porous insulator. If your layout is in a part of the country with swings in humidity, your bench work better be sealed on all sides with paint or sealer to keep moisture cycles of dry weather and humidity form causing the wood to expand, contract or warp. You need to cut appropriate gaps in rail to allow for expansion and contraction of the rail with temperature swings. I think the main difference is that I think the metal rails respond more quickly to heating or cooling than wood does to humidity and drying, but both problems need to be addressed unless you live in a dry climate where the humidity just doesn't change much.