If you want to create convincing model railroad terrain without the mess and weight of plaster, extruded foam insulation board is the go-to solution for many modelers, both new and experienced. Foam is a versatile material that lets you craft everything from rolling hills to dramatic mountain peaks, and the learning curve means that you don’t have to deal with a lot of mess before you get your scenery to look the way you want it.
The popularity of foam scenery construction stems from several practical advantages. Foam offers excellent strength despite the fact that it’s extremely lightweight. That’s particularly crucial if you need a layout to be portable or if your mounting situation is weight-sensitive.
Foam provides tremendous design flexibility and can let you easily modify terrain by cutting away sections or adding layers even after you’ve finished your build.
The carving process, even though it can be messy, is far less complicated than working with wet plaster or plaster-soaked cloth over cardboard strips. Foam doesn't have a working time limit like plaster, which means you can work at your own pace. Not to mention, a solid foam base makes installing trees, figures, and scenic details much simpler than with hollow hardshell construction.
Not all foam is created equal when it comes to model railroad scenery. The key distinction lies between Extruded Polystyrene (XPS) and Expanded Polystyrene (EPS).
XPS foam, commonly sold in blue (Dow), pink (Owens Corning), or green varieties at home improvement stores, is designed with a tightly packed closed-cell structure that makes it rigid, durable, and ideal for carving detailed terrain features. Its dense composition prevents the foam from crumbling into thousands of frustrating static-filled beads.
EPS foam, otherwise known as “bead board” or white Styrofoam, is not a good material for scenery work. Its open-cell structure with irregular spacing between cells makes it significantly less dense and prone to breaking apart during cutting and carving. No one wants to deal with clouds of lightweight particles that spread everywhere with the slightest air movement.
For most layout applications, XPS foam boards are available in thicknesses ranging from one-half inch to two inches. Thicker boards minimize horizontal joints between layers and can even serve as benchwork when properly supported, eliminating the need for plywood in certain situations.
The Wedding Cake Method
The most popular technique for creating hills and mountains with foam is colloquially known as the “wedding cake” or tiered method. This approach involves stacking successively smaller layers of foam to create the sloping contours found in nature. The process begins with cutting foam sheets to rough shapes that approximate your desired terrain, then gluing each layer together with wood glue or specialized foam adhesive.
Start with a small test section to develop your technique before tackling major terrain features. Spend some time studying photographs of real terrain.
Focus on building the general shape first and leave detailed contouring for later stages. The beauty of using the wedding cake method lies in its forgiving nature. It’s not critical that you lay out the groundwork with precision during the initial stacking phase, which means you can refine the shape as you get to the carving phase. In fact, intentionally creating a more random stacking pattern can facilitate realistic features like rock outcroppings and varied slopes.
When you glue layers together, apply a thin layer of adhesive between each sheet and weigh them down overnight to make sure they get a solid bond. Some modelers swear by Glidden Gripper primer paint for foam-to-foam adhesion, claiming it creates an unbreakable bond. Allow adequate drying time before moving to the carving phase.
The wedding cake method provides a proven starting point, but don’t be afraid to experiment with techniques that work for your specific situation.
Remember that scenery construction is forgiving. You can always cut more foam away, and even if you carve too much, it’s not too difficult to glue on additional layers.
Carving and Shaping
Once your foam layers are securely bonded, the real artistry begins. The carving phase is all about blending layers together and eliminating abrupt changes in slope angle. At this stage, you’re still working on general shapes rather than fine details. Different tools produce different effects on foam board, so experiment with various implements to achieve the textures you're seeking.
Essential carving tools include serrated knives or small saws for removing larger sections, utility knives and craft knives for finer details, Surform rasps for smoothing and blending, wire brushes for aging and texturing surfaces, and even simple items like the edge of a metal ruler or flathead screwdriver for creating specific effects.
Hot wire cutters can create smooth, flowing cuts but require excellent ventilation, as foam releases toxic fumes when cut with heated tools. Many modelers prefer the versatility and safety of manual cutting and carving tools. As you carve, concentrate on creating irregular, natural-looking contours. Real-world topography is rarely smooth, featuring rain-washed gullies, rock outcroppings, and subtle undulations that add visual interest.
The final shaping phase is where your scenery truly comes alive. Reference photographs from your prototype region or take your own pictures during day trips to capture realistic terrain characteristics. Consider where water erosion would naturally occur, where rock faces would be exposed, and how vegetation patterns would develop. These authentic details separate convincing scenery from obviously artificial terrain.
Finishing Techniques
Raw foam, no matter how well you carve it, doesn’t resemble natural terrain until it’s properly finished. Most modelers apply a layer of plaster cloth, lightweight spackle, or even diluted plaster over carved foam to create a hard, paintable surface. This coating smooths imperfections and provides a durable base for painting.
For rock faces, many modelers combine carved foam with plaster castings made from rubber molds. Hydrocal, an extremely fine plaster powder, captures superb detail when poured into highly detailed rock molds and dries to form dense, durable castings that resist chipping. Cast rocks can be applied directly to dried foam surfaces or pressed into place while the plaster is still setting, then blended together with additional plaster carved to match the castings.
Painting brings foam scenery to life through careful color layering. Start with an airbrush application of earth-tone base colors appropriate to your region. Artist’s acrylics work well for this purpose. Apply multiple thin layers rather than heavy coats to build up depth and color variation.
Specialized painting techniques enhance realism significantly. Washes, created by thinning paint and flooding it over an area, settle into crevices and simulate natural shadows. Drybrushing, where you wipe most paint off the brush before lightly dragging it over raised surfaces, highlights edges and worn areas where sunlight would naturally strike. Black washes in deep crevices, burnt umber in soil-rich areas, and light ochre highlighting on sun-exposed rock faces all contribute to convincing results.
Ground cover application completes the illusion. While paint is still wet, sprinkle real sand for texture, or use adhesive spray to apply sand after painting dries. Foam turf, static grass, and natural materials like dried moss add vegetation. The foam's solid structure makes planting trees and details straightforward, as items can be inserted directly into the foam base where they hold securely.
Many modelers document their foam scenery construction processes online, sharing techniques for everything from creating vertical rock walls by gluing foam layers perpendicular to the layout surface to carving realistic water-worn channels and gullies. With some basic tools and attention to natural appearances, any modeler can create convincing terrain, and that can really be the wow factor that takes your modeling from casual to artwork.
Check out the Green Stuff World Smooth Sculpting Set, hobby knives, and phenolic carving foam, as well as our whole collection of modeling tools to get yourself started with tools and materials.
- Written by Matt Herr