Permits and occupancy: Is there a law that exempts 1-2 family?

Hello, kind brownstoner folks, We’re in the midst of filing for renovation permits with the DOB for a four-story 1890s townhouse we purchased in 2014 in Clinton Hill. We have an architect who has submitted plans as well as an expeditor; both are knowledgeable about the process. We’ve recently hit a bump I didn’t especially foresee. My two simple questions, repeated at the end, are these (more background below them): (1) Why would we have to consider our house a single family and therefore file Alt 1 if we’re making it a two family, if the HPD, DOB and DTF all have it listed as a two family already, and (2) What’s the deal with (what our attorney says is) a law on the books that says that the above isn’t even relevant for a one or two family dwelling? And how do we get DOB to acknowledge this? Relevant facts: The house has no C of O. The DOB profile lists the house as B3-2 FAMILY DWELLING The Department of Finance classification is the same (B3-2Family) HPD LISTS IT AS 2 Class A units and Zero Class B units The home was owned by the same family for about 40 years, their heirs sold it to us. It was built as a one family house as were its neighbors in 1890, at some point converted to 2 family (see above) and then had various uses. We don’t have any documentation of that conversion but see references to records above. Its last use was basically a very underused single family with a renovated kitchen on the garden level an old kitchen upstairs on the top floor. Our mortgage documents and the appraisal that led to them list it as a 2 family dwellling. Getting the loan as a two-family was not a problem. As part of our renovations, we are going to convert the garden (basement) floor into a separate apartment, the kitchen is already in it and make an owners’ triplex above. There is currently a second kitchen on the top floor (not usable), but we’re going to put a kitchen for us into the parlor floor. One more wrinkle: The previous owners attempted to get a Letter of No Objection, which was denied for lack of enough information provided. When we were just about done with our DOB filing for Alt 2, it apparently just came to the attention of the plan examiner that the “current use” was a single family (from the plans, maybe?) and that we did not have enough information to support its “continued use” as a two family; If we persist in this we may have to file for Alt 1 which we really dont want to do (it’s not a gut reno, we’re not changing the size etc). I was really under the impression that if there was no c of o the HPD, DoB and maybe TF would be enough, plus the appraisal report. We spoke to the attorney that handled the purchase, and according to him, there are laws in place that say that anything below a 3 family dwelling is not subject to the same stringent code requirements, (sprinklers etc) that we fear we would be required to conform to if we filed for Alt 1\. In other words, he’s saying it doesn’t matter whether it’s a one or two family because the code laws don’t apply to 1 and 2 family dwellings. He also added that in some cases the only way to get this to be acknowledged was to sue the DOB (he wasnt trying to drum up business as he’s not the kind of attorney who handles that by his own admission) I would love some insight please (it has taken us two years to deal with the permit process though some was not unexpected, don’t even ask about the LPC): (1) Why would we have to consider our house a single family and therefore file Alt 1 if we’re making it a two family, if the HPD, DOB and DTF all have it listed as a two family already, and (2) What’s the deal with the law on the books that says that isn’t even relevant for a one or two family dwelling? And how do we get DOB to acknowledge this? Endless thanks for any light you can shed on this!