What are these scaffolding around NYC buildings all the time?(FAQ#8)

Those scaffolding or sidewalk sheds are part of a New York City Building Law concerning maintaining and repairing a building's exterior facade.  Specifically, it's called Local Law 11, and it's quite common place.

Local Law 11 requires an inspection every 5 years of a building's facade for building's higher than 6 stories.  So you can deduct that for a place like New York City, with 1000's of building's higher than 6 stories, you will see these scaffolding quite often.

The importance of Local Law 11 is to ensure the safety of the pedestrians and vehicles from a deteriorating building.  Brick work deteriorates over time and a loose brick or piece of debris falling from a high floor is a potentially dangerous occurrence.  

Every building that meets the minimum height standards of Local Law 11 has to comply and the management company of the building is typically responsible to hire the contracting companies that provide the scaffolding and sidewalk sheds, engineers to inspect the building, and  possibly architects to facilitate the process.

So don't be alarmed, if you see scaffolding outside of a building you are interested in buying an apartment in, the building isn't falling down, it's probably just time for the mandatory inspection of the exterior and barring any required repairs the scaffolding typically comes down relatively quickly.  

You can always confirm with the management why the scaffolding is up outside of a building and see when they estimate it might come down.