Building Extension Permit


    How important is it to have a city permit to an extension to a house – before we decide to buy it? I understand there are many properties with extensions built without permit but I want to weigh pros and cons before putting down an offer. Any insights from people here would be welcome.

    15 Replies

    1. If a valid C of O was issued at some point in time after the extension was built, would that mean that the extension is legal from a DOB perspective? If so, could the OP check to see if there are any post-construction C’s of O on file?

    2. Perhaps worth taking a look at any previous applications for Work Permits from the DoB. If, for example, a bathroom renovation was planned, and the filing documents show the rear yard addition, then it would be difficult for the extension to be termed ‘illegal’ as it was part of an application that was at some point approved by the DoB. The extension may then be recognized as existing non-conforming condition. Of course the alternate is to do a zoning study and determine if an extension would be legal, in which case you could plan on ‘legalizing’ it once you take possession.


    3. so much for a free country and buying your own house, then you still have to get a permit to do something to your own house that you pay for…..

    4. Oh I see. Then it depends, you maybe able to legalize it. When was the extension built and how did you find out it was built without a permit?

    5. Like I’ve said countless times, 90%+ of all buildings in Brooklyn have unpermitted work. And extension would be a fairly egregious offense but nonetheless, they are plentiful. Most likely it can remain but the problem is that if you do have to get a permit for something else, this will likely come under scrutiny and be a problem. If you plan no renovations that would require permits from here on out, I wouldn’t worry about it.

    6. I think OP is considering buying a building with an existing extension and there wasn’t a DOB permit for it.
      I bought a house with a small 1 room extension that had been there for generations (we found newspaper from the 40’s inside the walls). Got it fixed up – new interior walls and floor, new siding, new window, new roof. Later sold the house. Honestly I never thought about DOB permits and it never became an issue but maybe things are different with DOB from how it was in the 90’s and 00’s. Riskier to build a new un-permitted extension vs. keeping an existing one.

    7. Those illegal extensions were likely built some time ago- the Building Dept is more on top of things now. All it takes is one complaint about construction noise from a neighbor and you’re done for.
      Also, along with the DOB being more on top of illegal construction, they have recently changed code interpretations that could affect whether you are allowed to build out. Get an architect, this is what we do.

    8. You need to have an architect look it over to see if the existing unpermitted extension is something that can be legalized. It would need to meet zoning, fire code and other requirements. Give one of us a call, there are a bunch on the forum here.

    9. Thanks karhu. I think you’re talking about a creating a new extension. The house in this case already has an extension built without permits. How big is a problem this is usually? Should I be worried about getting in trouble later after I buy the property? What if not-so-nice neighbor or a tenant (has a legal one bedroom in basement) complaining later? thanks again.

    10. It is very important to have a permit to perform construction work. I don’t think you can get it done (especially for extension) without a permit. If you get caught, there will be a fine and then you need to apply a construction permit for removing all the work done without a permit. Before you buy the property, you should make sure zoning allows you to build additional floor area. Good luck.