I would go back to the 1870s and endlessly berate New York architects and builders for the next thirty years about their use of brownstone. Yes, it was cheap and very easy to carve. It’s been a plague on this city for 150 years. It’s been a plague in my work for 35 years and I’ve talked about this before.
The picture above is a small piece of the door surround at the front entrance to a rowhouse in Brooklyn. The stone was resurfaced with stucco in the past – probably in the late 1980s or early 1990s – so the outermost layer peeling off is the old stucco. Below that, we have brownstone doing was it does best: peeling off in sheets as it attempts to return to the layers of mud it once was.
There is no fix for this damage other than removal. You can remove the spalling outer layers and apply stucco or you can remove the entire stone and put in new stone, although it won’t be exactly the same material as the original quarries in New Jersey and Connecticut are mostly closed. The end result is that the vast majority of material that people see when they look at “brownstone front” buildings is actually brown stucco, which is something I could live without.
There’s no way to fix this situation now, so the only useful answer is that time machine and persuading, cajoling, or threatening people to use brick instead.