RC SLAB BEAM Clean Up Lines

[nocturne00]

Hi All;

I'm having some difficulty in cleaning up lines in my Sections, specifically where the Slab and Beam lines meet. It seems the beam and slab lines wont clean up as a monolithic structure, their lines wont trim at their boundaries. Initially I was able to do it by using the same Material(w/c is cast in place concrete), but now even if I use the same material, they wont seem to merge.

Any recommendation would be of great help. many Thanks

Below is a screenshot of my problem