Landmarks does not affect your ability to change the C of O, other than any changes to the outside of the property that you may be making.
In order to file for any building permit your acrchitect will need to get a notice of no effect from Landmarks. Of course if you are making changes to the exterior, anything that can be seen from the street will need to be approved by landmarks.
Why do you feel that you want to do this? There is not an issue with down useing a building. If you were going the other way, a 3 to a 4 there would be a problem, but down useing is not an issue. And leaving it as a 4 useing it as a 3 still gives you options down the road as well as avoiding the conversion process and R E Tax re-assessment issue.
Feel free to call me for further information.
Kathryn Lilly, Broker
Realty on the Greene, LLC
Only outside changes of your building, such as front facade, windows, doors, columns, architraves and other outside details, need a permission from Landmark for renovation.
If you need an architect who can help you with that, you always contact with me.
I am licensed contractor / realtor who is currently renovating a 4 story brownstone on a calendared block and I am changing the use from multi unit misc. to a 3 family c of o.
What will happen is that the Buildings dept. will automatically issue a 40 day hold on anything landmark or calendared. If you plan to alter the exterior you will have to get permission from the landmarks NYC division. Since I was calendared and nothing was being done to exterior we just waited the 40 days and that was it.
I suggest you go through HUB and that you use an architect that is familiar with it. This will expedite your plans tremendously.
Also keep in mind that you will have to sprinkler the entire building to conform to the new building code. This isn't cheap. I will say that I found a way to bring the costs down.
If you need a referral to an architect let me know.