Hi Jimmy,
I am using what appears to be polythene foam. It used as insulation for roofs and other areas here in the Philippines. It is available in huge rolls and sold by the metre. It is available in various thicknesses but I tend to go for around 20mm if possible. It is available with one or both sides covered in a metallic finish. This can be removed but a bit tricky.
I use clear mastic as an adhesive.
Once the piece of scenery is constructed I paint the exposed foam as soon as I can before too much rain gets to it. It is the monsoon season here but at the moment the rain is holding off. In the rain it can absorb water like a sponge. Painting the exposed edges reduces this problem. The material dries out fairly swiftly in the heat and sunshine.
I have used it for walls, with buttresses to provide strength. I have just completed a large bridge structure - looks a bit like Tower Bridge in London except that there are two levels and the bridges do not open. I have also made a signal box and roofed it with sheet metal.
Once constructed, and before painting, I use a soldering iron to score "bricks/stones" into the foam.
For paint I am using ordinary, oil based paint, including red oxide primer.
Here in the Philippines I am somewhat limited in the availability of suitable materials. So far I am pleased with this foam. However as I have only used this material for less than a year I have no experience of its longevity. Particularly bearing in mind the sun, heat and rain. But it's cheap enough to experiment. There is little strength to the material so either use: a frame; buttresses; thicker material; and form into towers (boxes). Be prepared, I suppose, for a shortish product life. But it's cheap enough to experiment.
Final point - it will not give the quality and appearance of a professionally made model such as those shown in an earlier post.
I hope this helps.
Cheers,
Tim
