Code: Underpinning (Building work / structural method)
Description: Underpinning is building work that adds new support under an existing foundation so a building can safely carry loads or sit next to a deep excavation. In NYC it is often required when you dig a deeper cellar or when nearby construction removes soil next to your wall.
Practical Meaning: Underpinning means a contractor will work directly under your foundation, usually by pouring short concrete sections one by one under the old footing. As a homeowner, you should treat this as high‑risk structural work and make sure there is a structural engineer, proper DOB permits, and insurance before any underpinning starts.
Where You May See It: You may see “underpinning” on DOB permit plans, structural drawings, contractor proposals, and foundation or excavation notes in DOB NOW or BIS. It can also appear in emails from a neighbor’s architect, in party‑wall agreements, or in engineer reports about movement or cracks.
Why It Matters: Poor or unpermitted underpinning can cause settlement, wall cracks, flooded basements, or even partial collapse, which can lead to DOB violations, vacate orders, and expensive repairs. If someone proposes underpinning near your house, you may need your own engineer and lawyer to protect your building and document any damage.
Source: More about Underpinning