some of the laws mandating that type of thing specify "if/when you renovate something, you need to bring it up to code, otherwise you can skate on the code"
this affects a lot of the little tiny shops in NYC. if you change your facade or bathrooms, they need to be made accessible. however, it's not the cost of renovation, it's that accessibility can entail many many square feet of space that is now inaccessible-to-make-any-money-from, making the rent much more unaffordable. so, renovations are still done, but meticulously match what any previous plans on file would look like.
The trades themselves don't pull permits because it's not about the permissionn, it's about using them. The towns don't care unless you've cut them out so much that they feel slighted in which case they'll send you angry letters about violations, demand a million bucks and you'll hire a $10k lawyer (another licensed trade, lol) who'll get you off for $1k.
Needless to say compliance is pretty low outside of the rich neighborhoods because normal people can't afford to tack $4k of engineering onto a "repave my shitty 2-car driveway" project or a $3k panel upgrade onto a "renovate my 50yo bathroom and add a couple outlets".
It's all shit and should be replaced with a much lower touch system that's cheap enough people can afford to comply with it. But there's so many parties in on the racket that it'll come crashing down before that happens.
The curb elements are made offsite. All you do onsite is to cut the stones to length if need be.
The challenge is properly anchoring them into the surrounding soil, and for that you need a concrete foundation. Basically, you make a gravel (or concrete) foundation, then you put down the curb element onto a few small pieces of wood, then you make a sort of mold cavity, and then you pour that mold full of concrete. Once that has cured, you put gravel to have an equal height with the road's gravel foundation on the road side and either soil or gravel on the pedestrian side to grade height - gravel if you want to place paving stones for pedestrians, or straight out soil if you want a grass siding.
You can see a few pictures and diagrams on how we do it in Germany here [1].
In Chicago, they concrete form the curb on site.
https://blackhawkpaving.com/wp-content/uploads/2021/03/Concr...
