Mark3D

Can you upload the plan as it is hard to see what is going on

Untick use soffit surface for ceiling in stairwell and loft playroom on room structure tab.

Upload your plan I will be easer to see what is wrong

Not sure what I am looking at but if that is a roof plain on the lower section that will stop wall the going to full height, you will need to drag it to the other side of the wall, if not upload your plan file so someone can help you.

Select the attic wall under root tab select roof cuts wall below.

I would first try using only the major contour lines for elevation data as chief will get slowed down if you use all minor contours , then if needed you could add some minor contours for correct shaping. if you have the cad file you could import to chief I think x12 may have import ability the video is using x13 Also if you have built the terrain and are having trouble upload your file you will probably get a fix

Select first floor room and unselect floor supplied by foundation below as your first floor has no floor.

You don’t have to use project management if the old way suits you , you can turn it off in preferences. You navigate to plan file in project management right click export disconnected plan then save and place on forum it will even zip it if you want

Upload your plan

See if that is better it still needs a bit of cleaning up, other may have a better way to do it Plans.plan

This post has similar question might help you

Image showing would be helpful

Check this setting

Also Share your chief plan file when looking for help on the forum not dwg

With terrains you cannot just put one piece of elevation data you need multiple elevation data, as if you have one elevation region the hole terrain will move to that height in relation to the settings in terrain perimeter. So a sloped block of land with an 8' slope you might have 4' elevation data and -4' elevation data you must control the terrain with more than one piece of elevation data