Roads for Your Model Railroad Layout or Diorama, the SMARTT Way




Introduction: Roads for Your Model Railroad Layout or Diorama, the SMARTT Way

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Almost every model railroad has villages and towns spotted across its landscape. What lends an air of reality to these features is the road work connecting them, turning a bunch of houses and shops and industrial structures into a living town that is a part of a larger world.  It may be tempting to just slap a coat of black paint on the bare wood of your tabletop layout surface and call it done, but the process involved in making a visually appealing road is not difficult or expensive. Many roads are asphalt based and this is an easy way for model railroaders to connect their towns.

I wrote this column for our December newsletter, , free for everyone to read and enjoy.

Step 1: Sketch Out the Road

Let’s focus on a road across a relatively flat area. Draw your road to connect the two points you want to connect on the surface of your layout.  If your layout is an open grid (no hard surface except under the tracks), you will need to attach a flat substrate like plywood, preferably screwing it into place with flat head screws that will sink flush to the layout’s surface. Don’t use something that will flex easily. Make your road as wide as you need using a scale vehicle for reference. A lane of traffic will be about 20 percent wider than a car. Multiply this by the number of lanes you want your road to have.  A meandering country road may have only one or two lanes. A highway would have more. You can also leave space on a city street for a parking lane on one or both sides of the street. Add a little extra width to your country roads to allow for a dirt shoulder. For this instructable, we'll make a sample road.

Step 2: Lay the Joint Compound to Create the Road

It’s easier to make your road surface before the ground cover in the surrounding area is installed, because the road process will raise some dust that might ruin your efforts.  The first layer of the road will be joint compound, usually used to cover or fix small holes or irregularities on drywall. It is available as an air drying pre-mixed substance in a tub or as a powder you mix yourself. We prefer the powder as it chemically sets, not air dries. Depending on the one you choose, it may set in as little as 20 minutes or as long as overnight.  You will need a flat spatula to apply the compound along the length of the road in the area you have marked. Do not work in too large an area at a single time, no more than a few feet. Mix the powder by adding it a few ounces at a time to a mixing cup holding a few ounces of water. Add more powder and keep mixing until it is the consistency of thick sour cream. If it gets too thick, add a few spoonfuls of water. Using the spatula, spread the material smoothly and not too thickly (no more than 1/16 to 1/8 inch thick). Try to remove any lumps. If you have mixed the compound well, there should not be any lumps. Don’t worry if there are a few minor scratches or other imperfections in the road surface. Let this dry, overnight if necessary.

Step 3: Sand the Road Surface

When dry, sand the surface of the road with 150-220 grit sandpaper. This will create a lot of dust so have a vacuum, preferable a shop-vac ready. Make sure that the shop vac is positioned so that the outgoing air doesn’t blow the sanding dust back in your face. Wear a dust mask and safety glasses if you can. You are going to smooth the road as much as possible, then vacuum again.

Apply a second thin coat of joint compound to fill the scratches and dips of your road. It does not need to be super perfect as real roads rarely are, but make it as smooth as you will be satisfied with. Let dry, then sand and vacuum again.

Step 4: Paint the Road Surface

Time for paint. For an asphalt color, try Woodland Scenics’ Asphalt water base paint. Brush it on and let it dry. You may need two coats. For a concrete road surface, Woodland Scenic makes a good Concrete paint too.  Before you paint, be sure that there is no dust left on the surface. You may want to wipe the surface with an alcohol dampened cloth or paper towel. If you don’t remove the dust, the paint will stick to it and not the road surface beneath, and the paint may peel up in subsequent steps.

Step 5: Dry-brush the Road Surface

Now you will need some white water-based craft paint, like that made by Apple Barrel or Deco-art. Spread the paint on a piece of scrap cardboard and dip the tip of a broad soft flat ended brush in the paint. Next, scrub the brush back and forth on a clean paper towel until there is almost nothing left on the brush to come off onto the paper towel. Stroke the brush back and forth on the road surface. It should leave a light layer of the white paint on the asphalt surface, lightening it, by catching the high points of the paint surface. The more times you repeat this step, the lighter and more weathered the road will become. This technique is known as “dry-brushing.” Some people scrub in a circular pattern others will go back and forth. Choose the procedure that is most comfortable and provides the most pleasing result. If you’re unsatisfied, you can always repaint the asphalt and begin again. Cover the entire road this way and let the whole area dry thoroughly

Step 6: Mask for Road Lines

If your road will have lines separating the lanes, you will need some narrow strips of masking tape. Many people lay out regular tape on a piece of glass and use a hobby knife to cut thin strips. If you are near an auto paint supplier, you can buy rolls of tape that is already very narrow.

If you are cutting your own strips from wider tape, you may want to consider using Scotch brand low-tack blue tape sold in the paint department of the hardware store. If you only have regular white or yellow masking tape, you can reduce the tack or stickiness by putting the sticky side of the strip on your shirt before laying it out on the road.

Lay the strips of tape out on either side of your road’s center line leaving 1/16 to 1/32 open space between. Fill the areas outside the tape with more tape so that only the area where the line will be is visible. Don’t press the tape down any harder than you need to in order to get it to stay in place. When you remove the tape later it might pull up your asphalt paint layer below. If the strip will be a dashed line, lay cross strips of tape to mask for that.

Step 7: Paint the Road Lines

Depending on the era and location, your lines may be yellow or white. Check photo references for this if available. Dip a brush in the line colored paint, using the same type of paint that you earlier dry-brushed. Wipe most of the paint off the brush. If you put too much paint down, it will seep under the tape. This technique is almost the same as the dry-brushing earlier, but with a little more paint on the brush. You will only concentrate on the exposed area between the tape strips. The masking will keep you from getting paint on the rest of the road.

After your road line is dry, gently peel back the masking tape. If you have avoided pressing down too hard and if your tape is not too tacky, then the asphalt should not peel up too. If you do have a few peeled spots, just touch up the asphalt and dry-brush the area again.

Step 8: Conclusion

A little sand or fine ballast blends the edges of the road into the surrounding terrain.

This technique is pretty easy and yields great results, but you might want to try it out several times on scrap areas before heading to the layout to perfect your technique.

Applying the same idea, you can now create other paved areas, parking lots, cul-de-sacs, etc.  By more complex use of the masking tape, you can make other markings like stop-lines, Railroad crossings, and more.

Good luck and now let’s hit the road!



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    18 Discussions

    this is perfect!!! :D

    Is there any thing wrong with black for asphalt and slate grey for concrete? That's what I've always done, but maybe I'm just being overly cheap... :)

    1 reply

    Thanks, that makes a lot of sense, I often blend paint colors for that same reason to!

    Great question! One of the great dioramists, Shepard Paine (I hope I've remembered the spelling of his name correctly) points out in his books that things in the real world are never simple plain colors. Tires are not truly black, concrete is not simply grey etc. The level of realism that you attain in your models is up to you. Model-making for the non-professional is supposed to be fun so you can do as little or as much as you like. How much effort you place into your efforts is your choice. For us, where realism is the standard goal, we strive to attain more than a single stock color. We present this as an option so you can consider moving beyond the basic level too.

    what i do for the lines (if you want dashed lines) is, you take a paper clip and unbend the outside end and dip it in yellow paint and then you just place it on the spots you want and it makes a nice yellow line.

    2 replies

    Another interesting idea! In the smaller scales like N this would be a great time saver, but only on straightaways, unfortunately. Bigger scales like O and G need more realistic edges and corners to "sell" the illusion.

    right it have this on my HO scale train set and it looks pretty cool but for the larger scales it needs to be a little bigger

    They are! and with the techniques you can learn on Instructables, not just from me but many autors, you'll find thay're easier than you thought! Give it a shot and make something!

    I notice in the photo above that the dry brush technique accentuated the brush strokes from laying down the asphalt color. Perhaps dabbing the wet asphalt paint with the end of a brush would give it a more realistic stippled look.. Also, curves in the road are usually wider than the straight parts.

    3 replies

    Good point. I'll have to give that a try in the future. We tend to vary our techniques depending on the area and the substrate.

    Strangely on projects, the road curves are as wide as the straight parts, but they modify everything when the road is begin made.

    Thanks, both of you. I had not been aware of the width issue on the curves. As we frequently have to be time conscious, there are certain elements that may be selectively ignored that are not obvious to most viewers.

    For example, real roads are not flat but when seen in cross section are convex at the center. This raised portion, called the crown sometimes, allows for drainage into the lower edges, which often have gutters, another element often overlooked.

    This kind of detailing is usually not necessary unless you are building an inticate contour map for a Dept of Highway Safety project. We let it go.

    Another element overlooked on roads is the super-elevation, or banking of the road on a curve. The outside of the curve is slightly higher than the inside allowing inertia (centrifugal force) to press the moving vehicle into the road surface for better traction. We actually do this for operational track work as it makes the trains run better.

    Keep those ideas and observations coming!

    awesome! you should post an instructable for the stonework above the red truck in the first picture.

    1 reply

    In step 8, if the painted surface is damaged, or comes up, you might consider doing a little 'Dept of Transportation' repair using more of the asphalt paint to put in 'tar strip' repairs just like the real world. a hypodermic syringe will make this easier to accomplish, and add even more realism

    1 reply

    I came here to declare SPAM, but found a well written instructable by a company that isn't pushing its wares at us. Nice job.