DOB and code context.
New York City Building Code Section 3309.4.3 is the trigger that applies to any excavation near a neighbor: no excavation 5 to 10 feet deep within 10 feet of an adjacent building, and no excavation over 10 feet anywhere on the site, may begin until the existing conditions of all adjacent buildings are documented in a preconstruction survey. Section 3309.4.4 adds monitoring once the work is underway, and TPPN 10/88 extends documentation to landmark buildings within 90 feet of certain excavation and foundation work. Where monitoring applies, Section 3309.16 calls for a written plan from a registered design professional covering device locations, reading frequency, tolerances, and what happens when a tolerance is exceeded. Our photographic record is the baseline those instrument readings get compared against.















