Giving Mesh thickness with additional requirements I have some meshes that are parts of hallways with different crossings but all walls have no thickness.
For purposes of rendering it in a game I program they need thick walls (for avoiding artifacts with shadow mapping).

How can I achieve this thickness with Blender? My three conditions are


No self intersections: I know about the solidify-modifier but the angles of my mesh make it so, that the new thickness intersects with itself which is not ideal (z-fighting).
UV-coordinates of all pre-existing vertices have to stay the same. We have a cool looking texture and the texture-mapping has to stay the same.
Stay tileable: The meshes get positioned next to each other in order to form a maze. This has to be possible with the thick meshes.


The outward appearance of the mesh is not important since they are only seen from the inside. Additional I should be able to do this within a day for round about 10 meshes.
I don't think you can use a modifier in this case. You will probably have to do it manually. 


Go into edit mode tab
select all a
extrude e
scale shift+y, (which will only scale on x and z.)


Now, if there are faces which are on top of each other (in the same place), you can try any of these options;


s, then y to scale along y.
Change pivot point to individual origins, then scale on y.
Simply adjust it manually.


It's hard to say what you should do, because I haven't seen the mesh, but this should help. Keep in mind, that I am assuming facing down your tunnel is the y axis. When scaling, you want to exclude the axis you are looking down, so that it only gets wider, not longer.

I hope this helped, please comment with any questions.