Greetings,

Why are you so sure that I am not allowed to mess with it? If the
firewall is 10" thick and I make a 2 inch deep trough and later fill it
in with mortar (and some outlet box holes) it won't change the
structural integrity. It won't make it so the neighbors can hear
through the wall. It won't change the fire rating to less than two
sheets of 5/8" drywall which is used for partition walls between houses
I have seen in the past. In short, I know it is probably safe. I am
wondering about the code issues. Just because something is safe
doesn't mean it complies with code. Of course local code could say
ANYTHING but I am not asking if this violates local codes that no one
here could know about. I am asking if it violates national codes or if
(for some reason I cannot think of) there is in fact a safety concern.


Why are you so sure everyone on the Internet is dumb and cannot provide
helpful advice? Why can't I tackle a project that I don't already know
how to complete before I start? Plenty of people complete projects
safely that they knew very little about before they started.

Update on materials used:
I have found some PVC coated MC suitable for direct burial in concrete
which has a smaller OD than 1/2" FMC so I have switched to using PVC
coated MC with concrete tight connectors.

Hope this helps,
William