I used stucco walls with a wall covering of stone or brick and the stucco is showing through in renderings. Never had this problem before x6. I have been using chief since vs. 9. It looks like z fighting but I don't know how to fix it. I was also getting in on the roof until I made the roof material 1" thick.
I started with the walls as pony walls but they were not behaving the way I would expect either. The lower material would not show up sometimes or if I changed the material it would not change in the renders.
The renders are just to show my customer's clients what a house would look like with certain options so having the proper wall type is not important, just the look. The plans are never used to build from.
Please let me know if you have any ideas that might help.