Seems to me there's plenty of examples of code requirements being enforced that were non-existent at time of construction. Fire escapes, stairwell smoke detectors and emergency lighting come to mind, as well as the handrails I mentioned.
Correct, any 3 or more, multi-family building built before the UCC came into effect in 1977 was required by the introduction of the NJ UFC (aka “retrofit” code, NJAC 5-70:1-4) in the mid/late 1980’s to be “upgraded” with various fire safety features. There had been several tragic fires, with multiple fatalities, in older buildings and the State introduced the UFC to upgrade the safety of older housing stock. The Code in effect when the UFC was introduced was the BOCA code, 1984 and 1987 editions. The UFC was amended several times shortly after introduction, and in the meantime the BOCA code was also updated, thus, the two applicable editions. An owner had to do the work to keep their green card. If they didn’t, then the building became unregistered and illegal for renting.
So if we think of a hypothetical JC brownstone, typical construction and layout, originally constructed in 1890 and converted to a 4-family in 1925, that building was mandated to be “retrofitted” by the UFC in the late 1980’s. Once that work was done on the building, inspected and passed, that was it – it had met the requirements of the UFC. It wasn’t required to have further upgrades – I gave you the citation to the NJR previously – just because a new code edition was released subsequently. However, if “rehabilitation” work is done on the building, that does trigger the need for updates to current codes – I’m oversimplifying for the sake of brevity, but see the rehab code for details (NJAC 5:23-6, et seq.)
What is NOT supposed to happen to that 4 family brownstone that met the UFC requirements in the late 1980’s and hasn’t had any “rehab” work since, is for an Inspector to come along and say, “Oh, now we have a new code, the 2006 UCC, and you don’t meet the requirements, so you need to do X, Y and Z.” But lots of Inspectors do it, and the JCFD does it. No one understands the rules, and the Inspectors pick home owners off in small numbers over time, so they get away with it…. But it isn’t what the Regulations permit or require.
This is why it is essential to know the specific edition of code that applies to your building – so you can push back if they ask for something crazy that comes from some later code edition. That said, for the simple, inexpensive, sensible stuff, I used to just do it anyway, even if it wasn’t actually “required” according to a correct application of the correct code edition. For the sprinkler I drew the line because of the costs and heavy-handed, threatening and intimidating way the FD approached me. They acted more like thugs than professional law enforcement officers and all the while they were wrong.