Owner Downstairs Wants to Convert Apt into Rental Unit

Hi,

I need a bit of advice from my friendly Browstoners. Our brownstone building is currently a three owner occupied building. We have the top two floors, lady below us has the 1st & 2nd floor and there is one other lady on the garden level. The lady downstairs wants to convert her 2nd floor into a separate rentable apartment. She would like to add a kitchen.

Now, looking at the building bylaws, I know that she needs to get our permission to do this. What I’m wondering though is, will the value of our place take a hit from allowing her to go ahead with her plans? The building does have a subletting policy which allows renting out the spare floor, but I’m wondering what the repercussions would be if she added a kitchen.

One last thing, we would like to have a roof deck installed and obtain roof rights. We would probably get these signed in exchange and she would give us her spiral staircase between floors that she would no longer need which we could add to ours (b/w floors 3 & 4) for access to the roof.

All in all, what do you guys recommend?

Any advice very much appreciated.