To Build or Not Build a Frame?

[RobertInOntario]

Question #1 - how thick is your foam, and what type of foam is it? If it is the blue or pink extruded type of foam 1.5 or 2 inches thick, you are probably okay going without a frame at only 3'x5' size. If it is the white foam, or less than 1.5 inches thick, I would recommend a frame. In my experience, thinner foam or the white foam is will sometimes bow slightly and needs support. The white foam isn't nearly as strong, and should have a frame no matter what the thickness.

I would not use plywood for a frame. Instead, I would build a frame out of 1x2 lumber. At that small of a size layout, I would simply build a rectangle with dimensions 2'x4', and glue it underneath the foam, leaving a 6" overhang on all sides. I would upgrade to poplar lumber as opposed to pine. It is straighter and has less knots. Putting an entire sheet of 3/4" plywood underneath the layout as a "frame" would be much heavier and not nearly as strong.

Thanks, Kevin -- all of this is helpful.

The thickness of foam is about 2" and it's green insulation foam. So it's very similar to the pink or blue kind, just the green/environmental version.

The frame you describe also sounds good although I may not need to go that route.

This leads to my next question or project! I was thinking -- that if I didn't need to create a frame -- I might extend the layout's length by 8" to 16" so I could add a sort of fiddle yard! I already have one siding at the left end of the layout where I can park one train -- I'd like to simply add another siding and improve the current siding.

This would obviously increase the layout's size to either 3x5.5 ft or 3x6 ft. I should have a little extra time in the next week or so, so I thought I'd try to sort out a few details before I started.

Thanks again,
Rob