Cost of adding a new floor

The true cost will be your sanity. Trust me on this one.

Based on my experience building up (just a bulkhead and roofdeck), I'd guess a minimum of $300k without any bathrooms or kitchens.

You may very well need to spend $25k on architectural, engineering, code consulting, and permit applications just to determine if it's even possible.

I am working on one right now (architect here) - a new set back floor in a landmarked townhouse. Minimum $500,000, with one bathroom and no kitchen. The mechanicals for the whole house may need to be changed, and the extra floor may even require stair hall enclosure due to fire regulations.

I was guessing around 150k. Thx for the input guys.

Target, how do you find out if it is possible to build up? For most brownstones can you only just add a little room onto the roof which is connected to the top floor apt, or can you actually add an entire floor?

How much you can add depends on landmarks and zoning... And of course the lower structure actually being able to handle another floor...

In brownstones, fire code can be an issue, too, especially if the building has only one common entrance and exit.

If you're willing to go through all the trouble associated with adding a new floor, you might as well buy an empty lot and build something from scratch.

Suggest you just add a realtively lightweight greenhouse and pergola, which will not require all the work of adding a new floor. You will need to make sure the roofing materials and joists can hold the weight, but you will be able to avoid a lot of the heavy work.

My wife and I are looking to buy a small townhouse in PS and in the listing it says it's pre approved to add a floor on top. We were just wondering how much and how long it would take. 300k to 500k is basically a NO for us lol.