Non-Manifold Geometry when using Subdivision

Hi all,

I’m a relatively new Blender user, and I’ve been taking some .stls from thingiverse and modifying them to create a certain effect. The first thing I often do with low-poly models is run a subdivision; however, when I run the subdivison, I immediately get non-manifold geometry, and cannot for the life of me figure out how to fix it. There’s no doubles, internal faces, etc. that I’m reading to fix on other posts. I am running into this issue mainly when I apply subdivisions to low-poly models. I’d upload the model, but unfortunately I can’t due to my new-user status.

Any help would be greatly appreciated.


Sub d modifier works best with a quad based mesh. You can select all faces and turn tris to quads, under face dropdown menu. But might not looks as you want


Just realized the non-manifold geometry was occurring before the subdivision this time. I just deleted all the non-manifold vertices and partially re-made the model, which fixed the issue.