third floor extensions no more?

Hey everyone. I am working with an architect and contractor on a project which involves, amongst other things, a proposal to take an unfinished third floor attic and make it a full size third floor, but also to extend the house back on all three floors, including the third floor (we have already confirmed we have enough FAR to do this and it would comply with the R5B zoning we are in). so based on this, the architect prepared initial plans, but after we reviewed them and ok’d it, they came back and claimed that we could not do any extension on the third floor, beyond the existing third floor space that exists. They are claiming that despite the fact that it complies with zoning because the house is a wood frame house and in a “fire zone” and is thus precluded. I asked them about this and they said all of brooklyn is a fire zone, and I expressed to them that this can’t be right or noone would be able to build a third floor extension in the borough. Also there are many recent similar extensions in the neighborhood all of which were permitted. They then claimed there was some change in the law in 2013 that would make it so that we can’t do any extension of the third floor, yet they couldn’t point me to anything that actually says that. The section of the administrative code they referred to for the “fire zone” thing i read to be likely inapplicable to an extension, but i wanted another opinion. I only know one person that did third floor work since 2013, and it is a bit odd that he did not extend it as he did the rest of the house, but only opened it up to make the existing third floor full height, so i wonder if there is any creadence to what they are saying. Is there any reason that anyone knows that I would be unable to extend the third floor, other than FAR requirements or anything in the basic rules of R5B zoning all of which the plans are in compliance with? Any help would be greatly appreciated. Thank you. Ps- i think this architect is an idiot. At an earlier point they claimed we didn’t have enough FAR to do the third floor work (again after having done the plans already). I looked at their chart because i knew this was wrong. I then found that they made major miscalculations on their chart of the additional square footage on each floor which once corrected (and they admitted their mistake), made clear that the plan totally was within the FAR limits. Especially because of this, i do not trust these people’s word, and since they cannot show me anything in writing that indicates what they now claim, i figured i’d ask you guys. Thanks again.