Top Questions Homeowners Ask About ADUs in NYC

Whatever the reason you’re here, ADUs have become one of the hottest – and most confusing – trends in NYC real estate. The rules are almost impossible to decipher, the costs are wild, half the time the city changes its mind mid- sentence.

Here are some of the questions homeowners just like you have and the honest-to-goodness answers that get past the fluff.

Can I rent my ADU on Airbnb?

Not if you wish to remain legal.

New York City’s short-term rental laws are harsh, and for good reason. The city supports the use of ADUs to provide permanent housing rather than for converting neighborhoods into hotel districts. Planning on renting out your backyard cottage to weekend warriors via Airbnb? No.

You have the ability to rent it long term (30+ days) and/or use it as your own residence. But nightly rentals? That’s a fast track to a $1,000-$5,000 fine. Nah.

Will adding an ADU increase my property taxes?

Probably—but not to the extent that you are afraid of.

In fact, generally speaking, if you raise the value of your home, the assessment will be higher. But, NYC does not regard square footage, but rather the income potential, of 1-, 2- and 3-family homes. If you aren’t renting the ADU – for example, your mother is living there free of rent – your taxable income remains relatively unchanged.

But check with a property tax professional prior to building an ADU. Even a small incremental increase today could translate into significant savings down the road – particularly if the ADU prevents you from having to move to a larger home.

What if my basement floods sometimes?

So unless your basement ADU has some serious waterproofing – and perhaps even a sump pump – you’re in trouble.

According to NYC’s building code, habitable spaces must be dry, safe, and free of molds. You can’t turn your wet basement into an art studio simply because it becomes damp after a rain and put a mini-fridge down there. You’ll want proper draining, vapor barriers and perhaps a backwater valve to prevent backups of sewage.

It’s not a free service, of course. But consider this, would you like to live in a damp, musty room? I didn’t think so either.

Can I build an ADU above my detached garage?

Yes – if you have the height and your garage is legal.

Detached garages have been built, never legally permitted, on many older homes in NYC. If yours is one of them, you must first determine how to legalize it. From there, you can typically build an additional 650 square feet on top of that, provided you stay within height requirements and lot coverage.

Zoning district is a pro tip. In some areas, second floors are not permitted on accessory structures. Better to find that out now than after you’ve bought the lumber.

Do I need my neighbors’ permission?

Not necessarily, but it’s good to keep them in the loop.

Luckily, NYC doesn’t require neighbor approval for ADUs . But once your new backyard unit casts shadows on their property, or makes parking impossible, or otherwise transforms their sleepy block into a rental alley, they will oppose. Complaints can also delay permits or cause additional reviews.

A coffee chat is worth a thousand emails. No, seriously. “A little unit for my elderly parents that I’m considering adding- just so you know” can save months of headaches.

Can I convert my garage into an ADU and still park my car?

That’s tricky.

If your garage is your sole off-street parking, then a conversion will eliminate it. And in most NYC neighborhoods street parking is a sort of Hunger Games.

Replace parking is, but, not required by the city. But let me ask you this: are you willing to drive around the block for forty-five minutes every single night? If that isn’t an option, perhaps a basement or attic ADU would be a better fit—or you could build a new structure that has both parking and living space (if your lot is able to accommodate it).

What’s the #1 mistake homeowners make with ADUs?

Not attending a pre-application meeting with DOB. Seriously.

Don’t simply engage a contractor and begin demolition. NYC’s regulations for ADUs are further complicated by an existing web of zoning overlays, special districts and variations to the code. Spending a half hour on the phone with someone at DOB can save you thousands of dollars in redesigns, delays, or refusals.

Second Key is here to guide you every step of the way. Let’s unlock the full potential of your NYC property—seamlessly, smartly, and beautifully.

Start your ADU journey today with a free property assessment.