Hervey Howe says:

Justin,
You are sacrificing a lot of wood for little strength. In my case I used 1×4 with a 1& 3/4″ strip glued and screwed into the top edge of the 1×4 to form a L beam. This is supported on 2×2 legs braced with 1×2’s.
I added 1×4 across the L beam I attached a 1×4 on edge to support the track base. These are placed where they will not interfere with scenery but I targeted around 16″ between each once the scenery was finished These were screwed into the 1&3/4″ strip on top of the L beam.
For track base I used 5/8″ plywood good one side. Since I was working off a plan I cut the track base to form as determined by the plan approximately 3″ wide. These are attached to the 1×4’s with a small wood bracket to allow for variations in elevations around the layout (rail line slope not holes in the floor).
Scenery is added by creating the form with narrow corrugated cardboard strips formed to the general desired profile attached by hot glue to the edge of the track base. This is then then overlaid with gauze impregnated with plaster of Paris (purchased in bulk on e-bay as ends of cast material). Once dry a layer of sculptamold is applied to give you the final form and something to apply scenic detail to.
Hope this helps. I found all this info prior to starting my layout on line if you wish to research more info.

Bob Van-Kempen says:

Good morning Justin
I have had a couple of goes at building a stable baseboard. In the end I used sheets of 1200x900x18mm ply as modules for the baseboard, braced around edges with 19x40mm pine. The baseboard has then been covered with 3mm cork sheet. This seems to have worked.

My original attempt used 20mm polystyrene sheet on top of the baseboard (which allowed me to carve out a dock area). But there was too much movement in the sheet (I think it might have been the hot summers in Queensland, Australia). This caused track alignment problems when I created ‘blocks’ in the track and slight twisting in spots. It was a salutory lesson to make sure everything is stable and aligned before adding ballast and scenery! 😊

Good luck with it.

Andrew Luchsinger says:

I use a 2 X 4 and 2 X 2 frame. Depending what I get for price will use either 1/2 in plywood or fiber/particle board or MDF. I found ceiling tile in place of foam or other types of material followed by cork for the road bed. It’s simple and gives me some good results. The best part about the ceiling tiles is that you can cut it easy and plaster of Paris will stick to it and does work well with the scenery materials I use.

Phillip Colins says:

I made a but-jointed ladder frame of 22 x 69 pine (PAR) with longitudinal bracing for rigidity. Over that I used a coarse chipboard, which I should have painted with oil paint. The chipboard was free; otherwise I would probably have used a more tighly compressed chipboard. In some ways plywood and fibre insulation board would have been preferable. Cost was a big consideration. Perhaps I was rather short-sighted, metaphorically as well as optically.