I read this on NextSTL and trying to understand what it means for housing renovations in the city. https://nextstl.com/2018/08/key-changes ... mediately/

> Under the new 2018 codes, if electrical, mechanical or plumbing systems are modified or extended in existing buildings, it appears they will now be required to be brought up to standards similar to new construction instead of being “grandfathered in”.

I read the article but I'm not clear if this is all buildings or just commercial buildings? If the statement above applies to residential as well, then adding just a single bath (apparently a Level 2 project) to an old house would require all plumbing and electrical in the house to be brought up to the new code? That would be prohibitively expensive in much of our housing stock. Hoping someone can provide clarity as I can't imagine that adding a half bath could trigger a full re-plumb and re-wiring of a house.