Trim walls to roof

[clauds1223]

Whenever I use the trim walls to roof setting in archicad, the walls trim to topside of roof, I want them to trim to the understand so they dont show,. 

Please help. 

Operating system used: Windows 11

[Lingwisyer]

Check the Intersection Priority of your relevant Building Materials and check if the top Surface of your roof is set as a Skin in your Composite.

Ling.