Building FAR

Look at OasisMap (http://www.oasisnyc.net/map.aspx), find the property you're interested in, and check the Location Report tab.

Where does ceiling height come into play. What stops someone with an FAR of 10 building something that is actually 12 stories high?
Maybe its a dumb question but I never understood what regulates someone building 9 foot vs 14 foot ceilings.

300, you may know this but available development rights cannot be determined by simply subtracting existing floor area from maximum permitted floor area. The analysis can be quite complex, typically done by an architect with experience in air-rights and air-rights transfers, taking into account factors such as existing lot coverage, side and rear yard dimensions, building overhangs, building height and other factors.

Truth, ceiling heights are determined based on permitted building heights which are detailed in zoning regs. So,
for example, you could decide to build a four story building with 15" ceilings or a six story building with 10" ceilings. Of course, a limiting factor would be the total floor area permitted.

Aaron2, cool site. Much easier to do these analyses today than 20 year ago!

Aaron, Thanks a lot. Very helpful. The building I was interested in has an allowable far of 10 and utilized of less than 3. As you may have guessed, I am exploring the lot line windows on a property and this tells me most likely I will lose it unless they have sold the air rights to some one else.

Ximon, I hear you. However, when the difference between utilized and available is significant, without paying some one to do a full study, it tells me that the probability of building up is high.

truth, Building height is rather complex. My quack understanding is -

One restriction of the total building height depends on the zoning.
Second is the width of the street and the width of your lot and how set back is your building from the street (driven by light for neighbors)

300: I had a similar issue when I was buying: lot-line kitchen window overlooking a brownstone (I'm on 15th fl). Fortunately, the air rights to the brownstone were transferred away a while ago, so my window is protected (I still look out to a brick wall 25 feet away, but it's better than nothing). I also had an architect who specialized in zoning issues give me some advice about the zoning across the street (which is different from my building's) , to get an idea of the likelihood that something would go up there. It will, eventually, though probably not during my ownership.

300, yes, makes sense there is some room for additional development though perhaps more in depth (rear yard) than height? Or perhaps some combination of depth and height if you do a setback? Please update us if you move forward.

In the apartment I am considering, it is clear that the commercial building next door can build up as they are utilizing small percentage of their FAR (saw that in the helpful link Aaron posted) and they are built full depth of their lot. Even if they have sold their air rights to some one, they can always buy the air rights from some one else - not easy but a smart developer can figure that out. I am assuming that the windows (5+) will be lost at some point of time and my bid will reflect that. If I do not get it, so be it.

Don't forget that we are in a time of constantly changing zoning (especially upzoning). Look what just happened in Midtown East and is likely to happen in East Harlem.

30, That is a good point. I always assume that if lot line windows have little value upto 5th floor. Above 5th floor, one needs to do more research.

300, so you are thinking that even though all remaining air rights may have been transferred, you might not be able to add windows along the lot line since the owner could theoretically purchase new rights? Never thought of that.

Low floor windows are not safe as they can just rebuilt with very high first floor without using any additional far. Research for possibility of buying is indeed very complex but is some one has far remaining, I assume they will build up for sure in 5 years. As least I would not to pay much for lot line windows. Say 2k per window each year for 5 years will be the max I would consider paying.

Btw, the lot line windows towards the back of the building are safe as the next door building has to leave a clearance at the back by law for light. Believe the requirement is 20 feet from the back of the lot. Most developers may even leave bigger clearance to get better light.

" In residential districts, the minimum depth of a rear yard is 30 feet, except in R2X districts. In commercial, manufacturing and R2X districts, the minimum depth of a rear yard is 20 feet. A corner lot is not required to have a rear yard. In commercial and manufacturing districts, and for some community facility buildings in residence districts, the rear yard may be occupied entirely by a single-story building up to a height of 23 feet. "
https://www1.nyc.gov/site/planning/zoning/glossary.page