The wall or column must intersect or extend beyond the top of the roof to be trimmed.
Trimming to roof will not cause a wall or column or any other element to grow to meet the roof.
Erika
Architect, Consultant
MacBook Pro Retina, 15-inch Yosemite 2.8 GHz Intel Core i7 16 GB 1600 MHz DDR3
Mac OSX 10.11.1
AC5-18
Onuma System
"Implementing Successful Building Information Modeling"