BC §3310: what counts as a NYC "Major Building"

What "Major Building" means

Under NYC Building Code §3310, a "Major Building" is a project that meets one of the following:

• 10 stories or higher, OR
• 100 feet or taller, OR
• A DOB-designated project (regardless of height)

Major Buildings get the highest tier of NYC site-safety requirements: a licensed Site Safety Manager or Site Safety Coordinator on site, a filed and approved Site Safety Plan (governed by §3304), and additional credentials (Concrete Safety Manager under §3310.10, FDNY Fire Safety Manager under FDNY rules) where the project's scope demands them.

The chapter further divides Major Buildings into two tiers:

Both credentials are issued by NYC DOB. Both involve documented experience and a DOB examination. The SSM credential requires more years and a higher-level exam.

The two thresholds: height and stories

§3310 ties the credential requirement to two thresholds: floor count and height in feet. You trip the requirement at whichever you cross first.

• A 14-story building that's 215 feet tall is over the SSM threshold (height-driven).
• A 16-story building that's 195 feet tall is over the SSM threshold (story-driven).
• An 11-story building at 145 feet is squarely SSC territory.
• An 8-story building at 90 feet is generally under the threshold entirely (other Chapter 33 rules still apply).
• A 10-story building at 105 feet is squarely SSC (right on the threshold for both metrics).

There is no waiver because your project is "only one story over the line." DOB enforcement is hard at the threshold. The threshold question is resolved at the DOB filing stage, documented in the project's DOB NOW application, and checked by inspectors from the first site visit.

What counts as a story

Story-counting under §3310 trips up development teams regularly. The standard methodology:

• Stories above grade count. A standard occupied floor counts as one story.
• Mechanical penthouses count. DOB counts them. Don't try to argue your top floor is a "mechanical space" to stay below the threshold.
• Mezzanines count as stories under most circumstances if they meet the floor-area criteria in the NYC Building Code's general definitions.
• Cellars and certain below-grade levels generally don't count toward the story threshold, but they may add to the height calculation in unusual cases. Confirm against your DOB filing and the height measured from grade.
• Roof bulkheads for stair and mechanical access typically don't count as stories, but the height they add can push a project over the feet-based threshold.

DOB Buildings Bulletins have addressed story-counting methodology in specific situations.

If your project is borderline, get a licensed manager to read the application before mobilization. We do this on intake calls at no charge.

Alterations, vertical additions, and demolition

The cleanest case is a new ground-up high-rise: 30 stories, obvious SSM. The trickier cases:

Major alterations. A 22-story alteration that's "just" replacing the curtain wall and reconfiguring the lobby still meets the threshold. Buildings keep their height during alteration, and §3310 keeps applying throughout the work.

Vertical additions. Adding a story to a 14-story existing building can put the structure into SSM territory partway through the project, especially if the existing building's height was measured below the §3310 line. The credential applies from the moment the addition work begins, not retroactively after completion.

Demolition. Full demolition of a building that itself meets the threshold requires an SSM during the demolition. This is one of the most common mistakes. Project teams think of SSMs as "new construction" credentials and overlook the demolition trigger.

Mixed scope. A project with both a new high-rise tower and an attached low-rise alteration usually needs an SSM for the whole project, not just the tall portion.

DOB-designated projects

§3310 also allows the DOB to designate any project as requiring an SSM, regardless of height. This authority is used sparingly but it does happen. Common reasons:

• Unusual structural complexity (transfer trusses, deep excavation in dense urban context)
• High-occupancy assembly use under construction
• Hazardous adjacent conditions (active subway infrastructure, occupied healthcare facility directly adjacent)
• Project history: a project that's already produced significant violations may be re-tiered by DOB designation

If your project receives a DOB designation letter requiring an SSM, the credential applies even if the building itself is below the standard threshold. Designation letters appear in the DOB NOW project record. Checking for them before mobilization is part of the filing review.

What credential each tier requires

Site Safety Manager (SSM). DOB-licensed individual. Required on Major Buildings 15+ stories or 200+ ft under §3310. Must be on site whenever active construction is happening. Maintains the SSM logbook. Signs off on major operations (concrete pours, hoist erection, scaffold builds, demolition phases). Coordinates with DOB inspectors. Holds stop-work authority and documents its use.

Site Safety Coordinator (SSC). DOB-licensed individual. Required on Major Buildings 7–14 stories or 100–199 ft under §3310. Same daily discipline as an SSM, scaled to the mid-rise project. An SSC license cannot be used on an SSM-tier project. An SSM license covers SSC-tier projects without issue.

Concrete Safety Manager (CSM). DOB-certified individual. Required under §3310.10 on Major Buildings with concrete operations. Inspects formwork, shoring, and reshoring. Signs off on each pour and coordinates with the structural engineer of record. The CSM is in addition to the SSM/SSC, though one person holding both credentials may cover both roles where project scope allows and DOB rules permit.

FDNY Fire Safety Manager (F-89). FDNY-certified under FDNY rules. Required on most NYC high-rise construction sites. Issues hot-work permits, verifies fire protection system operability, coordinates with FDNY chiefs. Independent credential from DOB SSM.

For a side-by-side comparison, see SSM vs SSC vs CSE.

DOB NOW filing path

The §3310 credential assignment is documented through the DOB NOW project filing, which is the current standard for NYC construction permit applications. In DOB NOW:

• The licensed SSM or SSC is named and their license number entered in the project record before permits issue
• The Site Safety Plan (§3304) is filed as a separate attachment and reviewed by the DOB plan examiner
• Any DOB designation letter, if issued, appears in the project record
• Credential changes (mid-project credential transitions, covering managers) are updated in DOB NOW through an amendment filing

PW1 paper filings are a legacy pathway largely replaced by DOB NOW for current projects. If your project still runs on PW1, confirm the transition pathway with your filing professional.

Decision flowchart

Use this in 60 seconds:

1. Is the building 15 stories OR 200 feet or taller? → Yes: SSM required under §3310.
2. Is it 7–14 stories OR 100–199 feet? → Yes: SSC required under §3310.
3. Below those thresholds? → Generally no SSM/SSC required, but check the DOB filing for any designation language.
4. Has DOB issued a designation letter? → If yes, SSM required regardless of height.

If step 1 is yes, also confirm:

• Concrete Safety Manager under §3310.10 if the project includes structural concrete operations
• FDNY Fire Safety Manager (F-89) for high-rise construction, coordinated through FDNY pre-construction conference
• Site Safety Plan filed and approved under §3304 before permits issue

Smaller projects below the thresholds may still need fire watch, OSHA-30 site presence, or other elements depending on hot-work scope and project conditions.

Common mistakes that produce stop work orders

The mistakes we see in the field:

1. Mis-counting stories. A 13-story building that turns out to have a counted mechanical penthouse becomes 14, then becomes 15 when the rooftop bulkhead is reconsidered. Suddenly the project needs an SSM, not an SSC. Catch this at the DOB NOW filing review, not at first DOB walk-through.
2. Treating an SSC as an SSM. An SSC license does not cover a §3310 SSM-tier project. The credentials are distinct and DOB enforces hard.
3. Assuming demolition doesn't need an SSM. It does, when the building being demolished meets the §3310 threshold.
4. Missing the DOB designation. Designation letters appear in the DOB NOW project record. Check for them before mobilization.
5. Letting an SSM credential lapse mid-project. License renewals are non-trivial. A lapsed license during active construction is a direct stop-work-order trigger.

A licensed manager review of the DOB NOW filing in advance catches most of these before they become enforcement events.

Bottom line

The §3310 Major Building threshold is conceptually simple (10 stories or 100 feet or taller) and operationally subtle. Get the threshold and credential right at the DOB NOW filing stage, hire the higher tier when borderline, and confirm the DOB record has no designation surprises before mobilizing.

Skilled Safety Management can confirm which credential your project requires in a 10-minute call. If your project needs an SSM, we can have one on site within 48 hours of contract signing.

Frequently asked questions

Working on a NYC project? Skilled Safety Management staffs licensed Site Safety Managers, Coordinators, Concrete Safety Managers, and FDNY Fire Safety Managers throughout the five boroughs. Send your project details through our contact form or call (212) 498-8863 for a fixed-fee proposal in 24 hours.