Floor Extension

I would not go behind the boards back it is frowned upon

I wouldn't do it. Not so much because it's behind the board's back, but because it "might" invalidate some known/unknown clause in your home insurance. If it doesn't affect your insurance somehow, then I guess why not. Though, what about when you want to sell?

i would first look to see if the building has enough FAR to do it and the proceed carefully. doing a minor renovation and a floor extension are different beasts. different materials have to be brought in and the noise factor will change as well.

treat lightly.

Also, if you do something like this you may unwittingly change the zoning allowance, which could hurt resale. If the space is zoned for a loft with, say, a 14' wide floor and you extend even one foot, you violate the original plan.

I know this can be a problem when people want to erect walls to add extra rooms--my parents had a loft years ago and wanted to create two bedrooms out of one larger room. Zoning laws allowed them only to build a 'partial' wall, one that did not go all the way up to the ceiling.

In the past saw two lofts in Tribeca where the units had open upstairs space (surrounded by wslls to conform to to conform to FAR. Sponsor, knowing that the space was valuable for a purchaser, had actually put in steel beams (hadn't needed to for the as-built), just in case someone wanted to "reclaim" the space in the future, which, of course, both purchasers had done. I assume the purchasers figured that no one was going to inpect for FAR compliance when they went to sell. They would, however, have had to explain the "extra" room vs. the condo declaration to future purchasers.

Adding on to a building to accomodate one piece of furniture sounds quite insane. You would have to do major structural work, add roof area, new exterior wall, etc. It would be the most expensive renovation in the city on a per sq ft basis. Also, the other commenters are correct about FAR. Most loft buildings are over built and will probably not have much FAR available. If it's a landmark district than you're really out of luck.

Crash, Anon is talking about adding on to the mezzanine area, the 2nd, internal area built into a double height space, the area over a closet or kitchen, for instance. It nonetheless seems like a lot of work for an additional small amount of space. I would just caution that it be good & sturdy so that it doesn't fall down, go boom.