ZBrushCentral

Clay buildup brush affecting the opposite part of the mesh

Hey, champions! Greetings to everybody. I am quite new to Zbrush and run into one very annoying issue while sculpting on relatively thin surfaces like wings for example. When I use clay buildup or clay brushes instead of adding mesh to geometry, instead of adding on top it is extracting from the opposite side of the wing and I just madly don’t understand why it is affecting the other part where it shouldn’t ( in theory, or at least according to a human logic). Anyone can please help me to understand what am I doing wrong here?
Appreciate any help!

It was obviously in the backface masking. But hey, very friendly community, appreciate that. Topic closed