The Grandfathering Clause: When Does It Apply?

The New York City Building Code prohibits apartments smaller than 400 square feet, yet you can rent apartments half that size.  What gives?  Aren’t those apartments illegal?


This is known as a “grandfather clause,” or when an old rule continues to apply to certain existing situations and a new rule applies to all future cases.  In the case of small apartments, the pre-1968 Building Code allowed microapartments, but the following Building Code instituted a minimum square footage of 400 feet.  The new rule doesn’t apply to existing apartments, but it has to all apartments built since.  Hence, old microapartments are technically legal.

The grandfathering clause exists because bringing old buildings up to new code standards every time the Code was revised is not only impractical, but cost-prohibitive.  In most cases, Building Code changes aren’t retroactive, and old buildings are simply left as-is under the clause.  However, not all code changes include grandfather clauses.  Generally speaking, code changes involving immediate safety and hazardous condition, such as updates to the Fire Code, apply universally to all buildings.

Additionally, grandfather rights aren’t necessarily permanent.  Grandfathered features are often required to be updated to the new code if they’re being renovated in some way.  For instance, suppose your bathroom was built before the Americans With Disabilities Act (ADA) was passed, which mandated accessible bathroom dimensions for the disabled.  If you chose to renovate your bathroom, the renovation would have to meet ADA standards.  If it didn’t, your new bathroom would be considered illegal, even though your old bathroom wasn’t.  The only way your renovation can avoid updating to the new code is if the necessary changes are impractical or financially unreasonable in some way.

It’s important to note that old work that was done without a permit can never be grandfathered in.   In the first case, the work was initially built legally and is only “illegal” now because the requirements of the Building Code have since changed.  However, work done without permits, even if it was a long time ago, was never legal to begin with.