paint/seal plywood & foam? is a free Model Railroad Discussion Forum and photo gallery. We cover all scales and sizes of model railroads. Whether you're a master model railroader or just getting started, you'll find something of interest here.


New Guy
I'm getting ready to put the plywood down (1/4") on top of that I plan on putting the 2" pink foam from Home Depot. Do I need to paint or seal either of these or both?



Wyoming native
The foam certainly doesn't need sealed from moisture. It's completely inert when it comes to water.

As far as they plywood goes, you'll get both yes and no answers. Some people think you HAVE to seal the wood or you risk significant dimensional changes with humidity (playing hob with your trackwork!), while others think paint is not really necessary.

For myself, I don't paint the benchwork. I humidify my basement in winter and dehumidify it in summer. Most of the time my basement stays in the 40-60 per cent humidity range, which keeps the wood stable. Occasionally it swings beyond that (like when I forget to fill the humidifiers), but it takes some time for the wood to absorb or lose water, so a day or two of high or low humidity isn't a problem.


New Guy
My basement somewhat remains the same temp and humidity as the rest of the house so I don't think that will be an issue.


Aaron, the biggest cause of warpage or distortion with plywood is caused by people not supporting it adequately or not securing it properly to its support. Make sure that you brace you plywood as much as possible and use plenty of screws to secure it (4 to 6 inch spacing max. for screws). This will prevent most of the effects of temp and humidity changes. I live in the heart of the South with very high humidity and my layout is in a garage without much enviromental control. I have yet to experience any problems with my plywood.

I don't use the foam on top, but I would not use 1/4 inch plywood for a top regardless of the foam. 1/4 is so thin that it is very hard to support to prevent sag. Do yourself a favor and go with 1/2". My 2 cents.
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