A lot of the information about the age of older NYC buildings is just wrong. Case and point are Harlem Brownstones. What we see around Harlem was mostly built over just a few decades – starting in the 1870s and continuing to about 1910. But if you look on places like Property Shark you’ll see dates like 1910 and 1920 on pretty much everything – that’s just wrong.

Our new expediter pointed out the way to figure out the age of our place, but you have to know how to interpret what you’re seeing. First, go to the DOB’s BIS (Building Information System). Find your building and at the bottom of the page there will be a link to “Actions”. Not all buildings have “actions”, if you have actions they’ll look like this…

(Click pic to see it full size)

Notice the line with “New Building”. But also notice it says 1984. The BIS system apparently gets confused with dates in the 1800s, so it’s off by 100 years – the real date is 1884.

But even that doesn’t work sometimes… Notice what it says for our sister/twin townhouse down the street…

Notice the date on the New Building line is 1918, but then see the line has NB 997-1884 – so the date is in the code number. Notice also that because they were all put up at once our building has the same code as the other townhouse since it was one big project – only the code on ours just has 84, instead of 1884. So it’s the code in the “number” column that’s most important.

Not all buildings have New Building actions. So you may need to look at the records for all the ‘twin’ buildings that were built at the same time. Of the 7 townhouses identical to ours, only the two shown above have New Building actions.

One other thing of note is that townhouses with mansard roofs are generally a bit older than the standard Harlem brownstones. For example the 3 remaining townhouses with mansard roofs on our block were built in 1880 – 4 years before ours. What’s a little odd is that 1880 was 7 years after the heyday of mansard roofs.