Jeff, do you feel there is a duty to upgrade an older home to today’s standards? I cringe at the word “mandated” and “will need to be replaced”. This is still America and buyers nor sellers don’t have to do as we say. I would phrase it a little less authoritatively, such as:
“There is no firewall separation between the garage and the residence, which is required by today’s commonly accepted construction standards…We recommend installation of a functional fire barrier for safety reasons.” (Emphasis added.)
Well if so, it must not have been enforced here in the Carolinas. I grew up in a home built in 1972 with a plywood separation (Mother still lives there). Most homes around here older than 20 years old do not have a functional fire barrier.
There’s absolutely no requirement to upgrade an older home to today’s code standards, but I would always recommend a firewall upgrade (separating living area from garage area) in older homes simply as a safety feature.
With this sort of thing, I mention that it may not have been required at the time the home was built, but that widely-accepted modern standards require it for safety reasons, then I recommend it be brought into compliance with modern standards.
This idea gets my vote which makes it an incomplete carport to garage conversion and repairs should be peformed to bring it into the accepted standard that has been in force since the first building code in 1927.