Why don't my walls touch the ceiling?

[bdillard1]

This one little thing is a great learning project for me - any guess on what I need to fix on this?    I'll probably make it a side vent fireplace since it isn't for heating but first I need to finish the chimey structure.

 

https://1drv.ms/u/s!AonCBRorVv74rGrvzyAazH7f4lD_?e=1W6OvX

[SNestor]

You need to define your fireplace walls in a different manner...watch the video

BDillard1 - Fix Interior Wall Definition - Watch Video

[bdillard1]

Thanks so much for solving it AND making it crystal clear with a video!