Geotechnical investigations and reports in New York City
Grant Engineering investigates subsurface conditions and prepares the geotechnical report that your design team and the Department of Buildings need. We work on new buildings, enlargements, and excavations next to existing buildings across the five boroughs.
What the investigation includes
- Borings and test pits, planned around your site and the proposed building
- Soil and rock classification, and groundwater observations
- Inspection of the borings and test pits by our own engineers (TR4)
What the report gives you
- Subsurface conditions found at the site
- Allowable bearing pressure and foundation recommendations
- Seismic site class
- Recommendations for support of excavation, underpinning and groundwater control where the project needs them
- A report signed and sealed by a New York Professional Engineer
Common questions
Do I need a geotechnical report for my DOB filing?
The NYC Building Code (BC 1803.2) requires a geotechnical investigation and report for new buildings, for horizontal enlargements, and for vertical enlargements or alterations that need new foundations or add more than 5 percent to the load on the existing ones. One- and two-family homes of three stories or less are generally exempt from the report, unless the job involves conditions such as underpinning or dewatering or sits in a flood hazard area (BC 1803.6). Call us if you are not sure.
How many borings will I need?
The code sets a minimum by building footprint (BC 1803.4.1): one boring up to 750 square feet, two for footprints over 750 and under 5,000 square feet, and one more for each additional 2,500 square feet. For one- and two-story buildings, test pits can take the place of borings. The engineer may call for more, depending on the site.
Why does an engineer have to watch the borings?
Borings and test pits are subject to continuous special inspection (BC 1705.6), which is reported to DOB on the TR4. Our engineers perform it.
What do you need from me to prepare a proposal?
The site address, the proposed plans or a description of the project, and any earlier borings or reports for the property.
Can Grant also design the foundation and inspect the work?
Yes. We design shallow and deep foundations, underpinning and support of excavation, and we perform the special inspections during construction.
How long does it take?
We can be ready to start on your project within days to a couple of weeks from contract signing.
Code references
NYC Building Code Chapter 18, Soils and Foundations: Sections 1803.2, 1803.4.1, 1803.6. Chapter 17, Special Inspections: Section 1705.6.