TL;DR: The Table of Terrain Materials

Tip: hot glue and corrugated cardboard gets you further than you realize.

plasticard: high-impact polystyrene sheet used for office signs
abs:        acrylonitrile butadiene styrene, the stuff used in Lego bricks
xps:        high-density foam used for heat insulation

Fiberboard e.g. MDF

Fiberboards are created by milling wet wood into fibers in high temperature
that are then pressed to boards. The pressing can be done using wet or dry -method.

For model building, you usually want the kind that is dry-pressed. You can recognize
a good fiberboard by checking that the fiber particles are small and not crumbly.

Technically, the denser the better, but you also need to have the tools to cut it,
and thus low-density fiberboard (chipboard) is more common.

uldf:       ultra-low-density fiberboard
ldf:        low-density fiberboard aka. chipboard or particle board for photo frames
mdf:        medium-density fiberboard
hdf:        high-density fiberboard aka. hardboard

Plasticard / Styrene Sheets

Plasticard is high impact polystyrene sheet. Plasticard term is used in the UK, styrene sheet term is used in the US.

You can get 3 mm thick plasticard from many office supplies, the are used for office signs. The thicker variety should be available in hardware stores.

• Thin plasticard (0.25 mm) is like paper.
• Thick plasticard (3 mm) is quite rigid.

You cut plasticard by score-and-snap. Scratch it with a sharp knife or scalpel, then bend it along the score, it should break cleanly. Clean the edges with a scalpel or file.

You can shape plasticard. Plasticard softens at 80°C and becomes malleable. Steam it over the kettle or soak in hot water. Heat gun also works but is far more dangerous.

XPS

High density foam aka. XPS (extruded polystyrene) is insulation foam that frequently used building wargaming and role-playing terrain. It's sold in both sheets and blocks. You can get it from hardware stores and it's the main material used to sculpt stuff like rocks and walls, but can also be used for the whole ground if thick enough.

High density foam brand names: Styrofoam, Polyfoam, Craftfoam, Reticel. Usually, the more dense the foam board is; the better and more expensive it is.

Extruded polystyrene (XPS) is not the same as expanded polystyrene (EPS). EPS is the one they use for packaging, XPS is the one used for insulation. EPS has very limited use because it's fragile and reacts to various chemicals used in terrain building.

Don't inhale XPS dust. Just like MDF, our bodies don't like it.

More natural bricks:

• cut XPS to bricks
• throw the bricks into a container with rocks
• shake

Vallejo Plastic Putty or spackle can be used to fill gaps in XPS. Stuff like Revell Plasto and Tamiya Putty will melt XPS. You can also use acrylic caulk.

Buy the densest XPS available in the appropriate size.

EVA

EVA (Ethylene-Vinyl Acetate) foam is frequently used for cosplay costumes and props. In Finland, EVA is also called softis in the live role-playing circles.

TL;DR:

I'd say EVA is usable for larger terrain and especially on things with curves.

XPS is surely better for small terrain pieces and adding intricate detail.

Compared to XPS, EVA is more flexible but harder to work with. You could call EVA "semi-squishy" in its default state. EVA is more troublesome to cut as it both requires a very sharp blade and dulls edges fast. EVA requires heating for it to take imprinted shapes.

You probably want to seal EVA with e.g. Mod Podge so it becomes less squishy, resistant to cracking and less porous so it takes paint better.

A snap-off utility knife is great for cutting of EVA. Having an adjustable, sharp edge is important. You should cut EVA in an angle to reduce tearing, not poking straight through it.

You could use a hot wire to cut EVA foam but it will easily leave you with jagged edges and toxic fumes. Possible, but not recommended.

EVA comes in various shapes but 2 - 8 mm thick sheets and rolls are common. You can also buy those toddler play mats but they come usually come pre-textured which can be a bad or a good thing.

Professional grade EVA is cheaper AND better quality than floor mats.

For example:
https://www.poly-props.com/
+ 5 grades of EVA foam, different densities.

You can use a heat gun to do EVA heat shaping. After heating the EVA, you can either bend it or apply texture on it.

To smooth an EVA surface, sand it, then heat it and finally smooth it with your finger while it's still warm.

Balsa

Balsa is a very light and cheap hardwood. It is frequently used for RC aircraft and miniatures.

Balsa is easier to cut and detail than most other wood. Even though technically a hardwood, it's really soft and keeps detail well.

The main, rather obvious, benefit is that balsa looks like wood. It is wood after all. You might want to use a wire brush to add more grains and stuff to enforce the illusion for your given scale.

• Use a wire brush to add more wood grains.
• Use an dark ballpoint pen or a sculpt tool to add knots.
• Use a hobby knife to gently add extra deep grooves.
• Use a hobby knife to chip a small chunk from the end of miniature balsa blanks.

Balsa is also a great material for miniature furniture.

Terrain Cloth

Fleece > Felt Felt creases.

• A big navy blue fleece is a good naval terrain cloth.
• Buy some dark green fleece. Hang on a washing line. Use spray cans of yellow, green and brown here and there.
• White fleece work great for a snowy field. Lightly spray with some pale blue.

Tip: See-through plastic cups work great for multi-layer naval battles. Ships on upside down cups, submarines on the table.

Dark fake leather can be used for urban terrain. There are so many varieties so your mileage may vary.

Don't get model railway grass mats for wargaming. They are meant to be glued on a flat surface, not to be rolled.

DAS Air Dry Clay

Quite moist, little messy but even pleasant while working with it.

You should dampen surfaces and tools with water, so it won't stick to them.

Tiger Hobby Clay

Hardens to hard but slightly elastic so won't break when dropped. Not crumbly or brittle at all.

Creative Beton

• not runny at all, more like a paste
• you can change to consistency with water but too much water makes it harden more brittle but more smooth

Sources

• Battlefields in Miniature, Paul Davies