I have never used roadbed in my yards. Just lay the track elements on the plywood surface, adhered, and then sprinkle real, sifted, garden soil in place to make the terrain look natural. I won’t claim rightness or perfection, but I have never been displeased with the results. If I used roadbed, it would require that much more sifted soil and liquid adhesive mixture to fix it in place.
I used 4x8 sheets of Homasote over 5/8" plywood (over 1x4 open grid benchwork) for my yard areas on the previous layout. While Homasote has many good properties, it was NOT perfectly flat and I had to do a lot of patching/sanding. I am thinking about using 1/2" or 1" foamular rigid foam board this time for my yard areas. And no elevated roadbed for yard areas in previous or new layout.
Check your foam with a straight edge. You will find it’s not as flat as one would expect - at least the extruded foam (blue or pink) that I bought.
There is no single perfect answer. Since I hand lay some of my track, cork’s disintegration over the years, and lack of spike holding, makes cork unsuitable. I’m now attempting doorskin glued to foam for roadbed. But I have to check where the track is going to make sure there are no subtle dips in the foam. In all fairness, the dips are normally towards the edges - the center will be thicker than the edges.
Fred W
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Hello All,
I use Woodland Scenics foam roadbed on a foam base.
GE Silicone Caulk; I or II, is used to adhere it to the foam.
The advantage of using silicone caulk is, if you need to reposition the roadbed it peels up easily without damage to either foam.
For some, the smell of the curing caulk is a deal breaker.
To attach the ballast I use powdered glue (now discontinued) mixed in with the ballast and wetted with 70% Isopropyl Alcohol and a few drops of India ink.
A similar product marketed as “Ballast Magic” is available from Delux Materials.
Hope this helps.
I bought a roll of 1/8" (3mm) cork underlayment from Menards. You can get a lot of roadbed out of a roll like that.
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That’s what I do - buy it by the roll.
Rich