Paving Plaster Roads

By Ty’s Model Railroad - 2/25/2012 04:40:00 PM

Completed model railroad plaster roads made from Smooth-It plaster and weathered with powdered pastels

I decided that the next step of my layout would be the roads. As always, I researched the subject online and found that the most effective method would be to build forms and pour the roads with a plaster product. First however, I needed to plan where my roads were going. I determined my road width at 2 1/2" and cut a square piece of cardstock the same width. After drawing the contour of one edge of my planned road on my layout, I used the template card to draw the opposite edge. This allowed me to ensure the road was always the same width. 

Double sided foam tape being installed on wood benchwork to make forms for plaster roads

Double sided foam tape being installed on wood benchwork to make forms for plaster roads

Once the outline of the road was drawn onto the layout, I installed 4 laser cut wood grade crossings where the road crossed the track. For the road forms, I used inexpensive foam tape that I purchased from a local dollar store. Woodland Scenics sells a similar product called Paving Tape, but it was unavailable at the one and only hobby shop in my city.

Masking tape being applied to protect track, grade crossings and turnouts from plaster road construction

First layer of Woodland Scenics Smooth-It road plaster being applied to forms made from double sided foam tape

I laid the foam tape on the outside edge of the road lines I had drawn. The tape I used was 1/4” wide, which allowed it to be easily pliable for any curves. Because my layout and grade crossings were not all level, I needed to use two, three, and even four layers of foam tape in several areas to allow the surface level of my road to be as level as possible. For a smooth transition between the different levels of foam tape, I always made sure the very top layer of foam tape was continuous rather than being stepped. This is very important when it comes to smoothing the top of the road.

Double sided foam tape being installed on wood benchwork to make forms for plaster roads

First layer of Woodland Scenics Smooth-It road plaster being applied to forms made from double sided foam tape

For the road material, I used Woodland Scenics Smooth-It, a special dry-mix plaster product specifically designed for building roads and other smooth surfaces. I mixed the Smooth-It powder with water until it was the consistency of cake mix. Working in small sections, I slowly poured the mix between the forms, spreading and leveling it with the top of the foam tape forms using a wide piece of styrene. I made sure I masked the top of the wood grade crossings with masking tape. That way I could easily level the roadway with the top of the crossings.

Double sided foam tape being installed on wood benchwork to make forms for plaster roads

First layer of Woodland Scenics Smooth-It road plaster being applied to forms made from double sided foam tape

After the first layer of Smooth-It had dried overnight, I applied a second thin layer, smoothing over any imperfections in the first layer and making sure the road was as smooth and level as possible. Once the second layer was completely dry, I carefully removed the foam tape forms. The roads were pretty smooth but needed further sanding to improve the surface and remove rough edges.

Second layer of Woodland Scenics Smooth-It applied to plaster roads with foam tape forms removed

Complete plaster road system after second coat of Woodland Scenics Smooth-It

Using 200 grit sandpaper, I sanded the road surface until I was satisfied with the smoothness. After I vacuumed all the dust off of the roads, I noticed some areas of my road looked bubbly, similar to the inside of an Aero chocolate bar. This was caused by mixing my Smooth-It too thin when I poured it. If you do mix it too thin, add more Smooth-It powder and stir until the bubbles disappear and let it sit for a few minutes prior to applying. To fill the air holes in the road, I simply added a thin layer of Smooth-It on top, making sure to press it into all the holes.

Leveled parking lot area made from Smooth-It road plaster for future freight station structure

Road and leveled circular cul-de-sac area made from Smooth-It for future model railroad downtown scene

I used three coats of gray acrylic paint for the road colour. I also coloured the wood grade crossings with India ink diluted with water. Once the gray paint had dried, I marked a center line on the roads with a pencil, using the center line on the same cardstock template I used before to measure the road widths. These lines would be a guide for the center line markings. I also marked out stop lines using the same method.

Stop line and center line markings drawn in pencil on a plaster road painted with grey acrylic paint

Sanded plaster road painted with grey acrylic paint

I masked the stop lines first and painted them with white acrylic paint. Once they were completely dry, I masked the center lines. To do this, I took blue painters tape and applied the required length to a piece of glass. I then cut the straight edge of the tape about 1/8” wide to make long, narrow strips. I peeled the narrow strips off the glass and very carefully applied it to the road, following the contour of the center line I previously marked. I also ensured the straight edge of the tape was always facing to the inside.

Stop lines masked out with masking tape and painted white on a plaster road

I found that starting at one end of the road and only sticking down 1/4 - 1/2” of the masking tape strip at a time worked best for getting smooth, straight lines. For curves, I found that holding the tape down with one thumb and positioning 1/4” of masking tape at a time with my other hand worked best. I then did the same with the second strip of masking tape, ensuring the space between the two strips was as equally spaced as possible.

Center lines masked out with narrow blue masking tape on a plaster road

I painted the lines with three coats of yellow acrylic paint. I then carefully removed the blue masking tape strips. Some small patches of the gray base coat did lift with the tape, which I easily touched up. Just make sure you save some of your original road colour if it's a custom mix! I found working in sections and not leaving the tape any longer than 20 minutes on the road greatly reduced the amount of paint that came up. Also removing the tape on a sharp angle helped, opposed to lifting in straight up.

Center lines masked out with narrow blue masking tape on a plaster road

Center lines masked out with masking tape and painted yellow on a plaster road

My roads were now complete, but looked a little too perfect and clean. To add some weathering and usage effects, I sprinkled a very small amount of black pastel dust down the center of each lane and smeared it with my finger. I used the same effect on the grade crossings as well. Signage and other small details will come later, but the main roadways are now complete and ready to serve the various areas of my layout.

Completed model railroad plaster roads at a turnout and grade crossing

Completed model railroad plaster roads made from Smooth-It plaster and weathered with powdered pastels

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2 comments

  1. Hello Ty, my name is Travis Getz and I have been working on a model town on-and-off for around 9 years now.

    I always told myself I would do a blog or a book one day, so everything was photographed digitally along the way. Then some bad sectors on some hard drives erased many of the photos!

    Anyway, I just wanted to let you know I really enjoy your blog and congratulate you on getting everything online and sharing your techniques with everyone. I have learned a lot from it, the wiring diagram and trick about dirtying the roads were both great.

    Well, all the best and keep up the great work... --T

    ReplyDelete
  2. what is the name of the foam tape that you bought from the dollar store?

    ReplyDelete