This has probably been solved before. I tried to search but could not find anything on the subject (didn’t really know what to call this issue). But anyway, I created a pillar and I am cutting some cracks into the side. The side I sculpt looks great, BUT if you spin the mesh around, the backside is extruded out where I sculpted on the other side of the mesh. I checked and symmetry and mirroring are both off (even though it’s not really the same thing). I am using a custom alpha, but that’s not the issue because it does it with the preloaded alphas too. Sorry for the basic question, but this never happened to me before.
If your brush size is quite large compared to the column then that may be causing the problem. It can also arise on thin objects. The solution is to turn on Backface Masking in the Brush palette.
Yeah, the brush was a bit too big and the pillar was thin. That backface masking worked though. I forgot about that option 
Thanks for the quick reply!