The May/June issue of MRH Magazine had an article about making retaining walls from rigid extruded foam, the same material that so many of us use for sub-roadbed these days. The author used 2-inch pink foam for his HO-scale walls. For my N-scale layout, using 2-inch foam seemed like overkill, so I used 0.25-inch blue foam, which is available at many of the same places that sell the 2-inch stuff. Otherwise, I used the same techniques as described in the article. The curved retaining wall below is 53-feet long by 26 feet high in N-scale. It took about 10 minutes to make the wall and about twice that to paint and weather it, allowing for drying time between applications of paint. The rough texture of the foam gives a fairly realistic look to the stones, at least to my eyes. And you can't beat the price! I think I can do a better job of painting and weathering, and I'll need to make some top caps, but I'm pretty happy with my first attempts. - Jeff And a slightly smaller straight wall.
I've tried this in the past, and my results were nowhere near as good as yours. One thing I found was that the finished product is very fragile. The slightest ding and you end up with a pink (or in your case, blue) gouge.
My completed walls are not fragile or brittle at all. They are actually kind of soft and flexible. You can dent them with a fingernail or screwdriver blade, but I have not noticed any tendency for the foam to chip or for pieces to break off. I've made over 300 (N-scale) feet of walls so far. The raw material is Dow Bluecor, which comes in fanfold bundles as shown below. If Bluecor is not available, look for the very similar Dow Protection Board. These products will be found in the insulation department of home centers and lumber yards. The sheets have a thin plastic film on one or both sides, which I peel off before using it for modeling purposes. A full bundle of this material would be sufficient to make 36 N-scale miles of retaining walls of the height I need! - Jeff
