Thanks Maru,
Those look good.
Bump map works well! If only there was a way to map translucency fraction as well.
are there any issues with using translucency and a small amount of refraction together? Ill test tonight and see how much time it adds to the renders. Mine above had only 0.1 refract.
I might stick to having 2 planes a few cm apart and having the hidden structure within them, for thats probably how it would be in my design (tho it would be two 20mm thick cellular polycarb sheets and a cavity between them and structure within that gap)
Another reason for having two planes, is that when I had a shadow cast onto the translucent plane from the outside, like an eave or tree etc, it would be a sharp defined shadow when looking from inside the building. Having 2 helps make this much more diffuse as it should be from within. Again, I'll have a look at how it affects the render times tonight.
Thanks again