First, I don’t want you to think my way is the only way. In fact, my way of building a roadbed outdoors is a modification of what I’ve seen others do. My way, which I call the “straight and narrow ladder” (SNL), works for me because I like flex track and since flex track inherently creates transition curves that look nice and allow trains to operate smoothly into curves. It's a relatively cheap and quick method of roadbed construction vs. concrete, wood/metal post, bricks, etc.
SNL as I use it is GROUND based. That is, it's meant to be constructed directly ON the terrain/soil. One might attach the upper part of SNL to posts high off the ground in order to have a railway running up high, but then it won’t be SNL.
The most important feature of using SNL is its flexibility. If you don’t like the way the layout is constructed, it's easy to remove the roadbed and change it around with little trouble. Another important aspect is simple construction. You could (and I have done so) literally build a lengthy section of roadbed, lay down track on it and run trains the same day.
Having a method with this ability gives the modeler the freedom to avoid creating every bit of the track design only to find out later that the route is unsatisfactory from whatever standpoint, but you're stuck with the roadbed as designed. You could rough out a design, put down the straight sections, fit the curves, tack down the track and try it out in a short time without worrying that something that doesn’t look right can’t be fixed unless a lot of work is undone.
The SNL method uses several materials that are available at big box hardware stores, either inside or thru their online website.
1/4” x2” x 8’ PVC composite trim
3/4” PVC pipe
2” deck screws
The amount of the materials list above is dependent on the length of track you intend to build.
The 2x4 lumber is used for two steps in the SNL process: 1) it provides the roadbed for straight sections and 2) it is cut into short 4” sections and used between the PVC trim on curves to keep the curves in line.
The PVC pipe is cut to short lengths, beveled at one end, and used to hold the 2x4s in the straight sections from moving. The PVC pipe length you cut is dependent on your soil – for loose soil, make the pipe lengths long – 1’ or more. If the soil is dense and doesn’t move much, the length can be shortened. Experiment to find out what is ideal for your situation. Err on the side of longer is better because we don’t want the 2x4s wobbling out of line since they act as anchors for the curves. The PVC pipes are attached to the 2x4s with the deck screws. But first the 2x4 must have a hole cut into it the size of the pipe. Use a boring bit the diameter of the PVC pipe you are using. I used 3/4” PVC pipe so a 1 3/8” boring bit did the job. Go about 75% thru the 2x4, not much more – you will have to pound that board and force the pipe on the other side to go into the ground without causing the pipe to poke thru the side you are pounding on. Drive a deck screw into the side of the 2x4 about 25% of the way up from the hole and drive it thru the pipe. Do another screw on the opposite side. You will notice the pipe swivels back and forth lengthwise a bit. That’s good for slight expansion and contraction of the roadbed along with track movement. Unless the lumber is over 6’, you only need two pipes. Otherwise, put a pipe in every 3’ or so.
Here’s a video showing how to make the 2x4 straight sections with the PVC pipe attachment:
Now for the fun part. Find a straight section in the layout design and install pipes into a 2x4 cut to the length of the straight section. Place the pointy ends of the pipes attached to the 2x4 along the proposed route and pound it in. If the terrain requires it, dig down or fill where the roadbed will go so the 2x4 rests along its entire length on the ground. I’ve found that making the top surface of the 2x4 even with the top of the proposed route gives more stability and hides the PVC trim pieces used for the curves looks better than having the sides exposed. This will require you to dig a couple of inches deeper along the route. Remember: these pieces of wood are food for insects so coat them with wood treatment and let it dry before installing.
Before filling the ladder:
After. Note the tops of the 2x4s are even with the grade, making it easy to attach track to them with nails or whatever.
More to come ...