Double sided faces in Blender 2.71

I am trying to create a small number of walls that require two sides and while I have found a number of posts on the subject for older versions, I am not able to find any that apply to this one. I tried turning the faces into very narrow rectangular prisms, but in order to get them thin enough, I end up with artifacts on render.

On a related note, there are a few areas in my model where faces touch, and I have removed as many walls as I can to prevent them from bleeding through, but there are still a few places where I just can’t seem to get them far enough apart to not interfere, while still keeping them close enough to touching that they still appear to touch, but it seems like this distance varies texture to texture. Has anyone else experienced this?

I’m not confident enough in my work yet to provide a blender file in a public space, but if necessary, I can probably provide one to someone that is open to helping me “bug test”.

Yes, it can be done in nodes with the Geometry node.
See pics.

Video here:

Great, thanks!