For many modelers, scenery is one of the most enjoyable aspects of the hobby. Prior to laying the plywood sub-roadbed a little forethought and planning goes a long way. Upwardly rising scenery features are easy enough. Even if your layout base is a simple slab of plywood, anything rising above track level can be formed simply by stacking hills and mountains on that base. It’s scenery that drops below track level that gets a bit trickier. Even if you’re modeling a relatively flat region, such as an industrial area or mid-western plains, you will need to allow room to drop down at least a little for features such as small streams and roadbed slopes. If you want more pronounced features, such as deeper ravines or more elevated roadbed, then the issue looms larger.
As a general rule, you don’t want to mount your plywood base directly on the bench work. That gives you ZERO opportunity to work in any downward dropping scenery. Begin by thinking through and planning what scenic features will drop below track level and by how much. Examples include sloped embankments, hills, waterways, and bridges. Once you know which features you want, and how far below track level they will extend, simply insert spacer blocks between the top of the bench work and bottom of the plywood. Depending on how much relief I want I use 1×2’s, 1×3’s or 1×4’s either laid flat or on end.
My preferred scenery base is extruded foam (the pink or blue material used in the building trades for insulation). This comes in thicknesses of 3/4″, 1″, 1 1/2″ and 2″. I then cut pieces of the foam and place them on top of the bench work as shown in the above photo. Once in place, the foam can be contoured with rasps, hot knives, or sanders.