Hi Users

I am facing a challenge in deleting the plenum from each floor of the
building. Initially, I have created a building with Flr to Ceil height of
9ft and Ceil to Flr height 4ft. Know I have to delete the plenum from each
floor, in this process I have increased the Flr to Ceil height to 13ft,
then tried to delete the plenum walls for each zone. After that, I am
trying to delete the plenum space but the "Next to the surface" of the
ceiling is which is selected as plenum are creating an error.

Please let me know the way to delete the plenum in detailed mode.

Thank you
Regards