topographic survey nyc
A topographic survey records the shape of the site rather than its legal edges: spot elevations, contours, the grade at the property line, existing structures, paving, walls, trees and visible utility structures. Architects and engineers need it before design because in this city the constraints are vertical as much as horizontal. A rear yard that falls four feet across its depth changes the whole approach to an extension. A cellar entry, a vault light, an areaway and the sidewalk grade all interact with what can be built and what the DOB will approve. Rooftop work has its own version of the same problem - bulkheads, parapets, existing mechanical equipment and setbacks all have to be located before an addition can be designed against them. We agree the datum before starting, because a drawing referenced to the wrong vertical datum is worse than no drawing.
A topographic survey records spot elevations, contours, existing structures, paving, walls, visible utility structures and the grade where the lot meets the sidewalk. Architects and engineers ask for it before design because in this city the binding constraints are frequently vertical. A rear yard that falls four feet across its depth changes the whole approach to an extension, and a cellar entry, an areaway and the sidewalk grade all interact with what the Department of Buildings will approve.
New York work references either the Borough datum or NAVD 88, and the two are not interchangeable. A set of drawings that mixes them produces errors that only surface once something is being built, which is the most expensive moment to find them. We fix the datum in writing at the outset and state it on the sheet. If your engineer has already specified one, that is the one we use.
the Bronx and Yonkers are the two places in this market where topography is a first-order problem rather than a detail. The ridge running through Riverdale and the Hudson slope above Yonkers put rock near the surface and drop several feet across a single lot, which decides retaining structures, driveway routes and whether a cellar entry is possible at all. Staten Island has real relief in the centre of the island too. In Manhattan, Brooklyn and Queens the ground is comparatively flat and the topographic work more often concerns roof levels - bulkheads, parapets and existing mechanical plant - than site contours.
Design work usually pairs this with an as-built survey where something already stands, and the construction stakeout that follows is set out from the same control. On a commercial transaction it is commonly ordered as part of an ALTA/NSPS survey.
How long does it take? Field work scales with site size and how much detail the designer needs. A rear yard is quick; a full block-through lot with a roof component is not.
These are usually asked for on the same transaction:
Records what was constructed, as constructed - required when a filing is conditioned on it or the build departed from the approved plans.
Learn More →Marking building corners, offsets and grades on site so what gets built matches what was approved.
Learn More →The national standard commercial lenders and title underwriters require on a transaction. Defined content, not a general drawing.
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